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I. 0).: n: M85 :3 LIBRARY 900:9 Michigan State University This is to certify that the thesis entitled Petrogenesis of Distinct Silicic Magma Types from the Lower Pleistocene Guachipelin Caldera, NW Costa Rica: Extensive Magma Mixing and Protracted Subvolcanic Residence presented by Chad Daniel Deering has been accepted towards fulfillment of the requirements for the MS degree in Geological Sciences gag, flag.) Major Professor’s Signature /2- w— 2605’ Date MSU is an Affirmative Action/Equal Opportunity Institution PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. MAY BE RECALLED with earlier due date if requested. DATE DUE DATE DUE DATE DUE 2/05 c:/ClFiC/DateDue.indd-p.15 Petrogenesis of Distinct Silicic Magma Types from the Lower Pleistocene Guachipelin Caldera, NW Costa Rica: Extensive Magma Mixing and Protracted Subvolcanic Residence By Chad Daniel Deering 'A THESIS Sumitted to Michigan State University in partial fiilfillment of the requirements for the degree of MASTER OF SCIENCE Department of Geological Sciences 2005 Professor Lina Patino ABSTRACT Petrogenesis of Distinct Silicic Magma Types from the Lower Pleistocene Guachipelin Caldera, NW Costa Rica: Extensive Magma Mixing and Protracted Subvolcanic Residence By Chad Daniel Deering Lower Pleistocene ash-flow deposits in NW Costa Rica represent sequential eruptions of high-silica (69—79% SiOz) magmas from the Guachipelin Caldera. Silicic magmatism such as this is uncommon in areas void of continental crust. However, the chemical variations within this suite of ash-flows are consistent with results from several different studies (i.e. Tamura and Tatsumi, 2002; Sisson et al., 2005) suggesting that partial melting of crystalline, calc-alkaline andesite or high-K basalts could produce these Silicic magmas. Chemical heterogeneities were discovered through evaluation of incompatible trace element ratios. Seven units were defined using the Nb/I‘ a ratio, which have a significantly wide range, from 3.8 to 29.4. Polytopic vector analysis (PVA), a multivariate statistical method, was used to characterize the relationship among individual units. The program defined four different end member or initial melts, which contributed to the generation of the seven units associated with the Guachipelin Caldera. This requires extended periods when the initial melts reside in subvolcanic zones prior to the inception of a particular eruptive event. Considering the temporal (<0.5Ma) and spatial (single caldera) constraints of this sequence of eruptions, significant chemical variations of the magmas have occurred, which require processes to operate on relatively short time scales. ACKNOWLEDGEMENTS For their guidance throughout this research project and meticulous review of this document, thank you to Drs. Lina Patino and Tom Vogel. Extensive help with sample collection in Costa Rica by Dave Szymanski and Beth Apple, providing an exceptional base of pumice fragments for key analyses, is also greatly appreciated. Special thanks to Bob Ehrlich for running the Polytopic Vector Analysis (PVA) workshop and Karen Tefend for her assistance with the EPMA and continued discussion of PVA. To my wife Heather, whose support and encouragement have elevated me to new heights. Most importantly to my son Dakota, who has perhaps sacrificed the most during my pursuit of knowledge. iii TABLE OF CONTENTS LIST OF TABLES .............................................................................. vi LIST OF FIGURES ............................................................................ vii I. INTRODUCTION ............................................................................ 1 II. GEOLOGIC SETTING ..................................................................... 5 III. GUACHIPELIN IGNIMBRITE STRATIGRAPHY ................................... 9 IV. METHODS ................................................................................. 15 l. Pumice sample collection ......................................................... 15 2. Sample preparation/ analyses ..................................................... 17 2.1 Bulk geochemical analyses .............................................. 17 2.2 Individual phase chemistry ............................................. 18 3. Modeling: Polytopic Vector Analysis (PVA) ................................... 19 V. RESULTS .................................................................................... 20 l. Geochemistry — bulk pumice ...................................................... 20 1.1 Major elements ............................................................ 20 1.2 Trace elements ............................................................. 79 2. Petrographic analyses .............................................................. 87 3. Mineral composition ............................................................... 91 3.1 Plagioclase .............................................................. 131 3.2 Amphibole ............................................................... 133 3.3 Biotite .................................................................... 136 3.4 Glass ..................................................................... 136 VI. DISCUSSION ............................................................................ 141 1. Origin of silicic magma: Partial melting/ extreme fractional crystallization of calc-alkaline andesite ............................................................ 141 2. Sources (HF SE: Nb,Ta, Zr, Hf systematics) ................................... 145 3. Limited fractional crystallization and melt segregation ..................... 153 4. Mixing/ Mingling ................................................................. 159 4.1 Geochemical and petrologic evidence ............................... 159 4.2 Polytopic vector analysis (PVA) ..................................... 160 5. Model for the petrogenetic evolution of distinct silicic magmas ........... 170 5.1 Guachipelin Caldera silicic melt generation ......................... 170 5.2 Magma differentiation ................................................. 173 iv VII. CONCLUSION ......................................................................... 176 APPENDIX A ................................................................................. 178 APPENDIX B ................................................................................. 185 REFERENCES ............................................................................... 195 LIST OF TABLES Page 21: Table 1. Pumice sample bulk geochemical data. Page 89: Table 2. Petrographic summary Page 94: Table 3. Phase chemistry Page 155: Table 4. Multiple Linear Regressions Page 162: Table 5. Initial melt compositions. vi LIST OF FIGURES Page 3: Figure 1. Geologic map taken from Acuna et al. (2000). Deposits in yellow represent pyroclastic flows related to the Guachipelin Caldera. Page 6,7: Figure 2a,b. a) Cross-section of the Caribbean Large Igneous Province in Central America. Variations in seismic reflections are interpreted as heterogeneities in the upper crust (taken from Salleres and Danobeitia, 2001; Figure 12). b) Reconstruction representing the convergence of the Cocos plate oblique to the Caribbean plate (taken from Meschede and Frisch, 1998; Figure 13). Page 10: Figure 3. Drawing of an individual outcrop illustrating the typical sequence found among the Green Layer, Santa Fe, reworked, and Pijije. Page 12: Figure 4. Composite stratigraphic column constructed based on interpretation of individual outcrop stratigraphic sequences. Nb/T a ratios are averages for all of the pumice samples within a unit. Ar-Ar dates from Vogel et al. (2004). Page 16: Figure 5. Field study area that lies between active arc volcanoes: Rincon de la Vieja to the Northwest and Miravalles to the East. The pumice samples were collected from road cuts and quarries along the South and Southeast Caldera margin. Map taken from Denyer et a1. (2003). Page 77: Figure 6. Alkalies versus silica, LeBas et al. (1986) classification diagram. Page 78: Figure 7. Pumice bulk geochemistry - major element variation diagrams shown versus SiOz. Page 80: Figure 8. Pumice bulk geochemistry — trace element variation shown versus $02. Page 81: Figure 9. Spider diagrams of representative pumice fragments from each of the seven depositional units of the Guachipelin Caldera. Samples normalized to primitive mantle value of Sun and McDonough (1989). Gray area represents entire set of Guachipelin pumice fragments sampled. Page 82: Figure 10. REE normalized diagrams of representative pumice fragments from each of the seven depositional units of the Guachipelin Caldera. Note the wide range of values the Santa Fe unit encompasses relative to the other units. Samples normalized to chondrite value of Sun and McDonough (1989). vii Page 83: Figure lla-d. a) and b) are cumulative frequency plots of incompatible trace element ratios Nb/Ta and Zr/Hf, respectively. Both a) and c) display distinct variations among units. The Nb/T a ratio demonstrates that clear compositional breaks exist within the Guachipelin pyroclastic deposits; however, Zr/Hf ratios do not separate the units as clearly. The Log-Log plots c) and d) are used to illustrate systematic variations among units based on the aforementioned ratios. A slope closer to one indicates a systematic control of the ratios by the element plotted on the X-axis, while slopes much less than one suggest less of a control by that element. (1) Slope is not given, but the Hf control on two parallel trending groups is evident. Page 86: Figure 12. The range of MN“ a fiom high-silica pumice of the Guachipelin caldera encompasses all of the high silica (SiOz > 65 wt%) samples along the arc. Distance along the arc is measured from Mexico-Guatemala border to central Costa Rica. Gray area represents high silica samples found along the are other than those fi'om the Guachipelin caldera. Page 88: Figure 13a,b. Photomicrographs (XPL) of pumice fragments showing representative minerals of the different units in the field area. Plagioclase, amphibole, biotite and quartz are the most common minerals. Note the resorbed quartz in (a), more than 90% of the quartz found in these pumice samples exhibit this disequilibrium texture. b) Typical amphibole and plagioclase grains at the edge of a glomeroporphyritic clot. Page 92: Figure 14a,b. a) Photomicrograph (XPL) of corroded plagioclase core with amphibole inclusions. This disequilibrium texture is found in plagioclase from nearly all of the representative units fi'om the Guachipelin pumice deposits. b) Photomicrograph (XPL) of a glomeroporphyritic clot and resorbed plagioclase from the Santa Fe unit. These clots generally include the presence of all of the primary minerals represented in a particular pumice fragment. The brush-like texture seen here along the margin of these amphibole were also common among units. Page 93: Figure 15. Photomicrograph (PPL) illustrating the presence of two distinct glasses in a single pumice fragment from the Pijije unit. Note the difference in crystallinity between the two apparently different magmas. This compositional variation is consistent with the presence of banded pumice fragments identified in the field. Page 132: Figure 16. The Liberia, Pijije, and Santa Fe-high (closed stars) plagioclase are all sodic from core to rim (28-37% An), with little variation. The Virginia unit has phenocrysts absent of any zoning as well as grains with reversed zoning. Both are higher in An (~50% An) than the Liberia, Pijije, and Santa Fe-high (closed stars) grains. The Santa Fe-low (open stars), Green Layer, and Salitral East all display normal zoning from as high as 65% cores to 36% rims. Only the Buena Vista pumice have clear oscillatory zoning. Each symbol represents points on a given grain. viii Page 134: Figure 17. Ba/ Sr vs. Sr/Ca plot for the plagioclase phenocrysts. All units are represented here with the exception of Pijije. Two separate trends are evident from core to rim of the phenocrysts. The upper group includes the Liberia and Santa Fe-high (stars). The lower trend includes the Green Layer, Santa F e-low (stars), Salitral East, Virginia, and Buena Vista, which display considerable overlap between cores and rims. Page 135: Figure 18. Major and trace element variation diagrams for the amphibole. Two distinct amphibole groups are clearly distinguishable. These are termed high and low-Mg amphiboles in the text. High-Mg amphiboles are encircled by a black solid line, low-Mg amphiboles are encircled by a black dashed line. The low and high silica groups within the Buena Vista unit are both represented and contain only the low-Mg amphibole. The Santa F e-low and Santa Fe high silica groups contain high-Mg amphibole and low-Mg amphibole, respectively. Page 137: Figure 19. Biotite major element variation diagrams. Biotite from Santa F e- high, Pijije, Liberia, and Buena Vista-high are shown, Salitral East biotite were not analyzed. There is some consistency between the major element (MgO, F eO, A1203) content of the Liberia and Pijije biotite. Liberia biotite are generally higher in K20, NazO, and TiOz than the Pijije biotite. Biotite from the Salitral East were not analyzed. Page 138: Figure 20. Major element variation diagrams showing the chemical array of the glass fi'om individual pumice. F eO, CaO, A1203, NaZO (not shown), and TiOz all show a negative correlation with increasing SiOz. MgO displays two sub-parallel negative trends and K20 shows the only positive correlation with increasing $02. Page 139: Figure 21. Trace element variation diagrams displaying the glass chemistry of selected individual pumice fragments. All of the units are not represented for each of the trace element diagrams due to lack of usable data. Page 143: Figure 22. Plot illustrating the variation in MREE (Dy) relative to the LREE (La) and HREE (Lu). Pumice samples with values of DyN/LuN < 1 could be the result of sequestering of the MREE by amphibole in the source. The subscript N denotes normalization to chondrite value of Sun and McDonough (1989). Page 144: Figure 23. Modified from Vogel et al. (in press). Blue dotted area represents experimental results from melting of high K-basalts, Sisson et a1. (2005). Red diagonal lined area represents the Guachipelin silicic pumice fragments. Dashed line encompasses the silicic pumice samples (Si02 > 65 wt.%) from the entire Central American Arc. Page 147: Figure 24a,b. Modified from Munker et. al. (2004). a) Interaction of slab melt with the mantle would generate magmas with high Sr/Y. Key incompatible element ratio Nb/T a shows no correlation with slab melt addition. Zr/Hf and Lu/Hf can be used as indicators of contribution of an enriched mantle component and slab melt addition, respectively. b) Illustrates the lack of a strong correlation between Nb/T a and other mantle depletion parameters (e. g. Zr/Hf, Lu/Hf, Zr/Nb (not shown)). This suggests ix variable degrees of mantle wedge depletion are not controlling the Nb/I‘ a ratio. Page 151: Figure 25. Variation diagram of Nb/I‘ a ratio versus Si02 illustrating that fractional crystallization of a silicate mineral is not controlling the Nb/T a ratio. Page 152: Figure 26. From Eaton (2004). Although there is an overall increase along arc of approximately 2.0960 6180 from the magnetite(Mt) analyzed, the Guanacaste (specifically the Guachipelin), are anomalously low. Page 154: Figure 27a,b. a) Fractional crystallization (FC) modeling using multiple linear regressions. Model is testing FC between the Santa Fe-low and Santa Fe-high. Yellow arrows used to indicate the pathways for Steps A-C. Step A represents the modeling within the Santa Fe-low (Parent: 010630-4h, Daughter: 010630-4a). Step B shows the model fi'om one of the least evolved Santa F e-low samples to an intermediate Santa Fe sample (Parent: 010630-4e, Daughter: 040707 ~2a). Step C represents modeling extending across the compositional gap within the Santa Fe unit from low to high (Parent: 010630- 4h, Daughter: 040708-6a). b) Spider diagrams comparing the observed and calculated trace element trends for each step. Note: Symbols used in spider diagrams are not consistent with coding used to identify individual units. Page 161: Figure 28. Example of multivariate diagram that represents the proportions of end-members for each individual sample. The A1203 diagram shows the 3 sub-parallel to parallel trends that correspond to the 3 trends clearly seen when comparing the relationship between EM 2 and EM 4. Symbols in scatterplot matrix are similar to those in the variation diagram, with the exception of the black asterisks: Santa Fe-high/low pumice samples and black squares: Virginia pumice. Page 164: Figure 29a,b. a) Ternary diagram demonstrating mixing proportions determined by PVA among the evolving IM 2+EV 2 and IM 1. Fractional crystallization trends represent the path consistent with modeling using multiple linear regressions. Open black stars: Santa Fe-low pumice and open purple crosses: Green Layer pumice. b) Ternary diagram demonstrating mixing proportions determined by PVA among the melt extracted from the IM 2+EV 2 and the IM 3 producing the hybrid Salitral East magma. Open black stars: Santa Fe-low pumice, open purple diamonds: Salitral East pumice, closed green triangles: Buena Vista-high pumice. Page 166: Figure 30a,b. a) Ternary diagram demonstrating mixing proportions determined by PVA among the highly evolved IM 2+EV 2 and 1M 1. Fractional crystallization trends represent the path consistent with modeling using multiple linear regressions. Closed black stars: Santa Fe-high pumice and open purple crosses: Green Layer pumice. b) Ternary diagram demonstrating mixing proportions determined by PVA among the melt extracted from the IM 2+EV 2 and the IM 4 producing the hybrid Pijije magma. Open red circles: Pijije pumice, open blue boxes: Liberia pumice, and closed black stars: Santa F e-high pumice. Page 168: Figure 31a,b. a) Ternary diagram demonstrating mixing proportions determined by PVA among the evolving IM 2+EV 2 and IM 3. Mixing between the least evolved of the Santa F e-low produced the hybrid Virginia magma. b) Mixing between the evolving IM 2 and IM 3 produce the Buena Vista-low magma. The Black open stars: Santa Fe-low pumice, black crosses: Virginia pumice, and green open triangles: Buena Vista-low/high pumice. Page 171: Figure 32. The general trends of magma evolution within individual units are indicated as Nb and Ta would be partitioned proportional to one another. Shifts in Ta concentration are influenced by mixing with end-member magmas with higher or lower initial Ta concentrations. Black dots represent the compositions of the four initial melts generated that would mix to produce the hybrid magmas (Salitral East: purple diamonds, Pijije: red circles, and Virginia: black crosses). Individual symbols represent pumice fragments as follows: Green Layer: purple dotted area, Santa Fe: black diagonal area, Buena Vista: green dashed vertical lines, and Liberia: blue dashed vertical lines. Page 172: Figure 33. Dehydration melting of three distinct crystalline calc-alkaline andesites produce the IM 2, IM 3, and IM 4 magmas. Partial melting of an anhydrous calc-alkaline source generates the 1M 1 magma. Nb/T a ratios for each initial melt (IM) are provided in the lower right comer of each box. Page 174: Figure 34. Summary diagram of the petrogenetic evolution of each individual pyroclastic deposit from the Guachipelin eruptive sequence. Solid double sided arrows represent mixing, dashed single sided arrows represent fractional crystallization, and dotted single sided arrows represent eruption event. xi I. INTRODUCTION A long-term problem is the origin of silicic magmas in geologic settings absent of old, evolved continental crust (for a review see: Vogel et al., 2004; Tamura and Tatsumi, 2002). If old, evolved continental crust were present, simply assimilating and/or melting that crust could produce silicic magmas. The southern part of the Central American arc is void of continental crust, but silicic volcanic products are common. Some have suggested that the generation of these magmas actually represents the development of new continental cruSt'CVogel et al., 2004). Several models have been presented to account for the presence of high silica volcanic products in arc settings. Tarnura and Tatsumi (2002) have shown that slab- derived fluids induce the formation of mantle melts that would eventually pond at the base of the crust. Subsequent melting at the base of the crust could produce intermediate hydrous magmas that later stall within the crust, reaching neutral buoyancy. Described as calc-alkaline andesites, partial melting of these previously emplaced crystalline magmas could produce silicic melts. Sisson et al. (2005) have shown through high pressure- temperature experiments that silicic magma could be produced by partial melting or extreme fractional crystallization of K-rich basalts. In another study of arc volcanism, Hildreth and Fierstein (2000) conclude that either partial remelting of already silicic crystalline rock with expulsion of the interstitial liquid or extensive settling of phenocrysts dominated by low-silica phases was required to produce the high-silica rhyolite of the 1912 Katmai eruption. The silicic pyroclastic ash-flow and fall deposits associated with the Guachipelin Caldera, Costa Rica (Figure 1), also display distinct chemical heterogeneities. Different — University of Costa Rica Central American School of Geology Geomorphologic Map Topographic Curubandé 3148 III lGN Scale 1250,000 — — Volcanic facies TEE"- Atfavgsado lavas D Aguacatales BUbeCI” [:1 Von Seebach subfaclee Caflas Dulces dacltlc domes Paleo-Rlncén de la Vieja Pyroclastic flow facles San Jorge subfacles Curubande subfacies ‘*' Pacayales subfacies Coyol subfacies Rincén de la Vieja facles 13:3 1:: Alcantaro 1:] Fluvial-lacustrian facles C] Colonia Blanca subfacles Guachipelin debris flow faciee Santa Maria subfacles Symbols 6 . Source m Avalanche scarp Inferred contact 3 Fluid movement Interpreted contact Inferred alignment ”‘3‘: Avalanche movement Observed alignment “"~ .m. Caldera border Crater m Escarpment slip Inferred strike/dip ‘\§; Rivers “'4 " Fan ‘\‘,\ Shear zone . v :7“- Nu m. I. ... ,1- lit. .(. I .2. 3 , Vigig... .1. .v . .. .. News E me ~‘—%» s '3 *1: K.“ .v v. 3% v. D .0qu .e-uhm sea a a “We a a @mw llow represent ts in ye (2000). Depos dera taken from Acuna et al. Geologic map 1 igure F lin Cal ipe flows related to the Guach lC pyroclast processes have been proposed to account for these chemical heterogeneities in other silicic deposits: 1) large-scale differentiation of an originally homogeneous magma body (Mittlefehltd and Miller, 1983; Baker and McBirney, 1985; McBirney et al., ‘1986; de Silva and Wolff, 1995); 2) discrete magma batches that represent partial melting or melt extraction from chemically discrete sources (Marsh, 1984; Bergantz, 1989; Sawyer, 1994; Eichelberger and Izbekov, 2000; Eichelberger et al., 2000); 3) magma chamber recharge (Eichelberger et al., 2000); and 4) further modification by magma mixing/ mingling, assimilation (Eichelberger et al., 2000). The objectives of this study are to define the stratigraphic sequence of pyroclastic flows associated with the Guachipelin Caldera based on variations in field relationships, petrography, mineralogy, and geochemistry. Based on these data develop a model that accounts for the origin and evolution of the magma. Along with petrographic analyses, whole-rock geochemical and mineral chemical analyses, and oxygen isotope analyses, polytopic vector analysis (PVA) is used to analyze the whole-rock chemical data. II. GEOLOGIC SETTING The tectonic evolution of the Costa Rican region is marked by the emplacement of several different magmatic components, which are collectively known as the Caribbean Large Igneous Province (CLIP). This structure consists of compositionally distinct constituents: mid-ocean ridge basalts (MORB), ocean island basalts (OIB), arc basalts, and flood basalts with a total thickness of approximately 40 km (Salleres and Danobeitia, 2001). Beginning in the Jurassic and Early Cretaceous (150 Ma), the first component, normal oceanic basalts (N-MORB), were generated at a spreading ridge between North and South America (Meschede and Frisch, 1998). This complex was later intruded, 90 Ma, by a large volume of basalt associated with the Galapagos hot spot which thickened the pre-existing oceanic lithosphere to ~15-20 km (Pindell and Barrett, 1990). Following the emplacement of the Caribbean flood basalts in the Late Cretaceous, subduction of the Farallon plate beneath the Caribbean plate was initiated, caused by the collision and suture of the Caribbean plateau and Lesser Antilles island arc (Burke, 1988). This convergence resulted in the production of are related magmas. Emplacement or underplating of are related mafic melts followed by crystallization of basaltic magmas is suggested to account for the heterogeneities in the upper mantle and lower crust, indicated by seismic refraction studies in the region (Salleres and Danobeitia, 2001). Seismic heterogeneities found throughout the upper crustal regime are consistent with the presence of crystallized magmas, which have been emplaced at various depths throughout the province (Figure 2a). Price et al. (2005) call this process preconditioning of the early crust by andesitic magmatism generated as a result of interaction between arc magmas and the lower crust. HIV“. K. . xx... . Vii. .1 . «.n.w.....lLv~«nhmw .mmEmmE 0:3me .0 cozmcozom: .995. £29.35 Rum—:0 6:8 2:38 8:60.). 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Hm. *0 ==0\ oo.xos_\ .\... .........U...... .. .H.” ............. .....,1- . .......... . ..... / xx 3. ..u M \m. «25:3 532 s The modern tectonic configuration began during the Late Oligocene to Early Miocene, when the Farallon plate separates into the Cocos and Nazca plates (Figure 2b). As the Cocos plate to the north moves in a NNE direction converging with the Caribbean plate, subduction is occurring ~20° oblique to the margin. The down dip angle increases with depth from 10° at 15 km, to 25° at 15-38 km, and to 43° beyond 38 km in depth (Norabuena et al., 2004). III. GUACHIPELIN IGNIIVIBRITE STRATIGRAPHY Ignimbrites associated with the Guachipelin Caldera are a direct result of the modern subduction zone magmatism and are between 2.06 and 1.31 Ma (V ogel et a1, 2004). These deposits are crystal-poor, poorly welded tuffs extending 3500-4000 km2 from the caldera margin, with a total eruptive volume of 25 km3 (Chiesa, 1991). A geologic map of the region is provided in Figure 1 (Acuna et al., 2000). The caldera is filled with several younger deposits including some originating from an adjacent volcano, the Rincon de la Vieja (Kempter et al., 1996). The sequence of ignimbrite deposits related to this caldera are known as the Rio Liberia Formation, which is further defined in this study using a combination of techniques including field relationships, previously acquired Ar-Ar dates, petrography, and bulk geochemical analyses. Initially, discriminations among ash-flow units were determined through field observations of physical characteristics such as mineral content. Therefore, only three units were recognized based on mineral types and abundance (i.e. biotite, amphibole, plagioclase). However, trace element ratios (Nb/Fa) reveal the presence of distinct pyroclastic units. Geochemically distinct units within the otherwise indistinguishable pyroclastic deposits provide the basis for a more comprehensive stratigraphic sequence. Identifying the stratigraphic relationship of the chemically variable ash-flow units is a prerequisite in determining systematic changes occurred. A detailed description of the chemically distinct units is covered later in the discussion. An example of an individual outcrop stratigraphic column that is based on both physical and geochemical variables used to define the units is illustrated in Figure 3. 6.....5 ncm €35.59 6". Scam :98... :85 9: 90:5 .056. 85:53 .moab 9: 9.6.6:... 8850 3336:. :m .o :E:.oo afamazgm .m 2:9... em... 1.0m0w1.<1. zwmmw . .- - .52- m“. 525 EB... 02. s s z .. 3. sea in... 8.383 42.22.2628“. .. E- w”. 525.53.. :85 3:55. .513 5.9 @5383 23 omxmozmm. 8.9 95-883 . . . - - m: : . .0 9m 883 5.” MEEQ 50.: man. 3.6. 3.32 3.953 o... Scam 2 .3. "@2030 5.8. .82. 0%.? £82 "cornea; mOEOHDO 12:05.92. 10 Separate stratigraphic columns at different outcrops illustrate the variations in the units caused by differences in the lateral extent of ash-flow transport from the caldera margin. The incompatible element ratio of Niobium (Nb) and Tantalum (Ta) are used to define the units included in the stratigraphic columns. Details regarding the determination of the seven units are provided in the discussion. The base of the Guachipelin volcanic suite is marked by a paleosol followed by a distinct pale Green Layer (Figures 3—4). The Green Layer ash-flow unit varies in thickness from 0.1 to 5.0 meters and typically consist of lapilli-sized pumice, with amphibole and plagioclase phenocrysts. The next youngest unit is the Santa Fe-low (Si02 <72 wt.%; Figure 4). This unit ranges in thickness from 6.0 to 15.0 meters, with tan-gray pumice distributions normally graded or in swarms, ranging in size from 2-30cm. Glomeroporphyritic mineral clots of plagioclase, amphibole, and Fe-Ti oxides and light pumice banding are also indicative of this unit. The Salitral East is above the Santa Fe-low and this sequence is observed in only one outcrop (Figure 4). This unit is similar to the Santa Fe-low in deposit thickness (~6.0 m), pumice distribution (normal grading), color (tan-gray), and range in size from 4-20 cm. Pumice mineralogy is dominated by plagioclase and amphibole with small quantities of biotite and quartz. The next unit in the sequence, the Santa Fe-high (Si02 > 72 wt.%; Figure 4), is also found in contact with the Santa Fe-low (Figure 3). This ash-flow sheet ranges in thickness from 0.5 to 1.0 meters with randomly distributed tan-gray pumice ranging in 11 #03. ..m 5 .omo> E0... mount .<.:< 4.5 m $5.3 moEEwm 8.8:: .omomEn. o5 .o ..m .2 $929.» 2m 8...: 2.32 .moocozaom 2:35:95 aobSo .3223. .0 5.52925 :o :33 “022588 5:28 2:35:96 ogmanoo .v 959“. B>m_..:o.20,.. .. .. .5 3.3.3 :0. .93. 590 1. . . _ . on. Sm - NO.m..v $4M NN.m_. Aw“. va wu— macmm 50.038. ,. . on. «$8 1 mm 8.3 5.3 .mm. .mmm. .EEmm . ..: ......,.-.. .. 1.0 30. 5.61. 520 .. .wéfimonovo. . mu. Em - NO.wA 5.3" om.mp \Amu. 59 w“. macaw swam Exam .._. _ . \v\ 8.1 52 a. 9...: m. a...“ a; 9. «.595 >m -No.w.v,.-.,. ~2an 5; 9m. 32> mcozm mhdfimwd >m hoax 3% as. ea... :cD a usage ...... - 83:8 8:25 fine-KANE? .. 1 a: . MANN-£3 ,m.- .. I 59:8 12 size from 6 to 12 cm. Pumice mineralogy is marked by plagioclase, biotite, and quartz with small quantities of amphibole. Some Green Layer unit pumice are also found mixed within the Santa Fe-high ash-flow sheet. Contact between the Santa Fe-high and the next youngest unit, the Pijije, is reworked, a feature consistently found where the Santa Fe-high is in contact with the Pijije (Figures 3-4). In addition to the coexistence of Pijije and Santa Fe-high pumice across this reworking contact, Green Layer unit pumice. often occurs below it. The Pijije ash-flow unit is white or pink, ranging in thickness from 3 to 40 meters. Lithics are typically found in these deposits. Pumice fragments are 2 to 15 cm with mineralogy consisting primarily of plagioclase, biotite, and quartz with trace amounts of amphibole. inferred contacts with the Buena Vista (above) and Ar-Ar age dating. Deposit thickness and pumice size data are not available. Primary mineralogy consists of plagioclase, biotite, quartz, and small quantities of amphibole. Pumice fragments from this unit were dated at 1.47 Ma (Vogel et al., 2004). Similar to the Liberia, the Virginia lacks any stratigraphic control, deposit thickness, or pumice size data. Only one outcrop is used to indicate the possible sequence of this unit above the Liberia unit (Figure 4), which places it below the Buena Vista. Pumice contain plagioclase and amphibole. A distinct physical contact exists between the Liberia and Buena Vista (Figure 4), the youngest unit in the sequence (1.31 Ma) (V ogel et al., 2004). There is no deposit thickness or pumice size data. Like the Santa Fe unit, the Buena Vista unit can be divided l3 into two groups based on Si02 content (Buena Vista-low, SiOz <72 wt.%, and Buena Vista-high, Si02 >72 wt.%). These pumice samples were collected without stratigraphic control and are therefore assumed to be randomly distributed within the ash flow. Primary mineralogy consists of plagioclase and amphibole with small amounts of biotite and quartz found only in the high SiOz group. The composite stratigraphic column in Figure 4 incorporates the interpretation of all the individual outcrops illustrating a possible eruptive sequence. Dating of the Monteverde Formation, below the Guachipelin sequence, at 2.06 Ma by previous workers (Alvarado et al., 1993; Gillot et al., 1994) constrains the complete eruptive sequence to less than 0.75Ma. l4 IV. METHODS l. Pumice sample collection Images in this thesis are presented in color. The collection of over 380 pumice fragments from the region S-SE of the Guachipelin Caldera by students and faculty from Michigan State University and the Universidad de Costa Rica began in July of 1999 and continued through the field season in July 2004. The locations selected for pumice sampling were chosen to encompass the region that is suggested to represent the pyroclastic deposits of the Guachipelin Caldera (Kempter et al., 1996; Acuna et al., 2000) (Figure 5). Samples were taken from a combination of road cuts, active quarries, and natural outcrop exposures near the network of roads extending away from the Caldera rim. Samples from July 1999 to October 2003 were taken from outcrops chosen to represent the different eruptive products, but were collected without stratigraphic control within field identified units. Breaks in depositional units were determined based on the physical characteristics of the deposits as a whole and the individual phenocrysts in the pumice fragments within them. These characteristics included pumice color, distribution and frequency; mineralogy; and soil horizons. Subsequently, bulk geochemical data from these pumice samples revealed the presence of several distinct units within field identified eruptive ash-flow deposits. During the final field season in July of 2004 a different approach to sample collection was undertaken. Pumice fragments were obtained in stratigraphic order from individual units, attempting to constrain the geochemical boundaries that were apparent within some of the field identified eruptive deposits. 15 .Amoomv ._m «m .350 Eat :oxE gas. .599: 9830 38:58 ucm :58 23:03. moEmaa ucm 330 :59. E2. 38260 925 8.3.3 oo_E:a 9:. .fimw 05 9 mm=m>§2 ucm $255.62 9: o. m_o_> m_ mu :oo:_m $850.? 08 o>=ow 5953 mm: 55 «98 33m 29”— .m 2:9". .5! 28:0ng / 52 2852.88; .. 232:5 3882 650.9 >53th 238.5» 2:802 650.9 539.0 :33 53...... 2:9 363$ 2889.83: =33 355$ 5230 .55 accuseoam ///'.// =3 :chfiao 8:325» 2:800... Aesoé 2%: l6 2. Sample preparation! analyses 2.] Bulk geochemical analyses Over 320 samples were prepared and analyzed for bulk geochemical analyses of major and trace elements. Hand samples selected for analyses were chosen based on analyzing the complete mesoscopic variation and to eliminate weathered samples. X-ray fluorescence (XRF) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA—ICP-MS) analyses at Michigan State University use fused glass disks. Samples were first trimmed of all weathered parts then rinsed in a sonic bath for ~10 min. After drying overnight, the fragments were pulverized in a chipmunk crusher and then finely powdered to <5um using a ceramic flat plate grinder. Three grams of this powder were thoroughly mixed with 9.0g of lithium tetraborate (Li2B4O7) and 0.5g of ammonium nitrate (NH4N03) as an oxidizer, all within 10.00005g, in a platinum crucible. This mixture was then melted at ~1000°C in an oxidizing flame for ~30min., while being stirred on an orbital mixing stage. The melt was poured into platinum molds, which are cooled on a hot plate at 400°C for approximately 5 minutes, before removing for final cooling over a 20 minute period. The fused discs were then analyzed using a Rigaku S/Max X-ray fluorescent spectrograph. XRF major element analyses were reduced by the fundamental parameter data reduction method (Criss, 1980) using XRFW IN software (Omni Instruments), while XRF trace element data were calculated using standard linear regression techniques. For LA-ICP-MS trace element analyses, a Cetac LSX200+ laser ablation system was coupled with a Micromass Platform ICP-MS. The Cetac® LSX-200+ is a Nd:YAG laser with a frequency quadrupled to an UV wavelength of 266 nm. The analyses were 17 done using continuous ablation (line scan) for three minutes. Strontium, determined by XRF, was used as an internal standard. Trace element data reduction was done using MassLynx software. Prior to any calculations, the background signal was subtracted from the standards and samples. Element concentrations in the samples were calculated based on a linear regression method using BHV O, W-2, JB-l, JB-2, JB-3, JA-2, JA-3, BIR, QLO-l , AND RGM-l standards. 2.2 Individual phase chemistry Eighteen samples were selected for electron microprobe (EPMA) analyses at the University of Michigan. These samples represent both the bulk geochemical and physical variations observed in the deposits. Microprobe analyses were performed using a Camera SX 100 EPMA equipped with five wavelength spectrometers using an accelerating potential of 15 kV, a 6 um beam spot size, counting time of 3 min/ mineral, and a 10 nA beam current. The following phases were analyzed for major elements: plagioclase, amphibole, biotite, Fe-Ti oxides, and glass. Trace elements of individual mineral phases and glass analyzed by EPMA were determined using Laser Ablation Inductively Coupled Plasma Mass Spectrometer (LA- ICP-MS). The location of each point analyzed was recorded for consistency between (EPMA) and (LA-ICP-MS) analyses. Laser ablation parameters used included a spot size of 25 am for plagioclase and 50 pm for amphiboles and glass, and frequency of 20 Hz. The ablation mode was depth profile, where the sample stage was raised at a rate of l um/s. The detector was activated before ablation to capture the transient signal. After ~0.3 min of data acquisition, ablation was initiated and continued for 5 sec. The first 0.3 18 min of data acquisition was used to measure the background. Once the ablated material reached the detector, the signal for the different elements was clearly observed in well- developed peaks. Results were quantified using the height of the peak above background for each element. The concentrations were calculated following Norman et al. (1996), with NIST 612 glass as the external standard and calcium determined by microprobe analysis as the internal standard. 3. Modeling: Polytopic Vector Analysis (PVA) Polytopic Vector Analysis (PVA) is a multivariate statistical method of analyzing populations of samples that are related by mixing. There are three parameters needed to define a mixing system: 1) the number of end members, 2) the composition of each end member, and 3) the relative proportion of each end member in each sample. PVA is used to estimate all three parameters from the bulk geochemical analyses of the pumice samples (for details see appendix A). 19 V. RESULTS 1. Geochemistry - Bulk pumice 1.1 Major elements Major and trace element data for pumice fragments are provided in Table 1. Samples totaling less than 96% are excluded from the discussion. Major elements have been normalized to 100% in the figures. The Guachipelin pumice fragments range in composition from dacitic to rhyolitic (66-76 wt.% Si02) (Figure 6). Variation diagrams show the chemical array for major elements as silica increases (Figure 7). The pumice samples can be divided into two groups based on Si02 content. First, a low silica group ranging in composition from 66 to . 72 wt.% includes samples from the Green Layer, Santa Fe-low, Buena Vista-low, and Virginia units. The second group consists of high silica samples, 72 to 76 wt.% and includes Santa Fe-high, Salitral East, Pijije, Liberia, and Buena Vista-high. There is a slight overlap with a few samples from the Virginia, Pijije, Salitral East units that plot outside their respective silica group. Magnesium oxide, Fe203, CaO, A1203 and TiO2 decrease and K20 increases with increasing Si02 (Figure 7). In addition, there are three parallel A1203 trends. One trend includes samples from the Green Layer, Santa Fe-low, Virginia, and Buena Vista-low. An intermediate trend includes the Salitral East and Buena Vista-high, while another trend includes the Santa Fe-high, Pijije, and Liberia units. 20 Table 1 Pumice sample bulk geochemical data.(Green Layer) Major element oxides (wt.%). trace elements (ppm). Sanmle 040707-6C 040708-38 040708-5A 040708-5B 040707-3A Location Longitude 85.33° 85.38° 85.38° 85.38° 85.24° Latitude 1 052° 1 069° 1 070° 1 070° 10.57° XRF analyses Si02 69.78 67.34 70.05 68.06 68.50 Ti02 0.49 0.53 0.48 0.49 0.51 Al203 16.32 18.73 15.96 17.27 17.13 F6203 3.96 4.33 3.64 3.89 4.20 MnO . 1 , 0.14 0.17 0.08 0.08 0.16 M90 0.54 0.53 0.53 0.66 0.48 CaO 2.70 2.53 2.56 3.23 2.80 Na20 2.10 2.40 2.61 2.70 2.49 K20 3.95 3.41 4.05 3.59 3.70 P205 0.03 0.03 0.04 0.03 0.03 Total 96.02 95.91 96.1 8 96.84 96.64 Rb 81 69 83 69 62 Sr 383 359 373 454 380 Zr 1 98 202 209 208 1 92 Laser ablation lCP-MS analyses Y 34.21 30.16 22.22 16.93 24.79 Nb 1 1.69 12.65 12.30 12.40 9.52 Ba 1890 1921 1819 1696 1598 La 48.13 41.72 33.17 28.62 27.13 Ce 82.36 94.29 62.29 58.04 65.90 Pr 14.12 1 1 .84 7.46 5.94 6.61 Nd 54.26 44.48 25.65 20.39 24.30 Sm 8.49 7.41 3.97 2.49 3.78 Eu 1.59 1 .50 1.08 0.86 0.98 Tb 0.89 0.80 0.54 0.33 0.50 Dy 5.09 4.31 2.95 2.03 3.02 Ho 0.84 0.74 0.55 0.31 0.53 Er 1.84 1 .74 1.38 0.56 1 .27 Yb 1.99 1.96 1.93 1.29 1.62 Lu 0.24 0.27 0.28 0.15 0.22 Hf 2.97 3.55 4.33 3.43 3.34 Ta 0.43 0.54 0.60 0.49 0.36 Th 7.00 8.25 8.00 7.39 5.69 U 4.39 5.14 3.63 3.33 2.89 21 Table 1 cont. (Green Layer) Sample 040707-38 040707-30 040706-1J 040706-1 K Location Longitude 85.24° 85.24° 85.17° 85.17° Latitude 10.57° 10.57° 10.52° 10.52° XRF analyses Si02 70.79 67.42 69.29 69.18 Ti02 0.39 0.57 0.45 0.48 A1203 16.30 17.33 16.37 16.20 F9203 3.1 9 4.33 3.29 3.52 MnO 0.06. t 0.11 0.08 0.09 M90 0.51 0.99 0.67 0.76 CaO 2.28 3.23 3.10 3.03 Map 2.81 2.98 3.03 3.01 K20 3.66 3.02 3.68 3.69 P205 0.02 0.02 10.03 0.03 Total 96.58 96.77 97.17 97.19 Rb 77 51 73 74 Sr 316 382 440 430 Zr 137 221 196 193 Laser ablation ICP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Hf Ta Th U 9.15 1436 22.40 45.32 5.33 19.24 2.98 0.72 0.44 3.63 0.37 5.56 2.77 24.99 9.69 1432 26.82 55.89 6.32 22.69 3.29 0.91 0.44 2.86 0.52 1 .14 1 .65 0.21 3.74 0.33 5.66 2.74 21 .19 1 1.51 1687 32.13 58.58 7.24 25.65 3.72 1 .10 0.46 2.64 0.48 1 .05 1 .57 0.19 3.15 0.48 6.55 3.24 22 21.70 1 1.94 1728 33.82 62.25 7.93 27.75 3.84 1.1 1 0.47 2.73 0.49 1.03 1.51 0.20 3.05 0.47 6.62 3.71 Table 1 cont. (Santa Fe) Sample 040707-63 040706-3A 040706-38 040708-6A 040708-2E Location Longitude 85.33° 85.17° 85.17° 85.38° 85.39° Latitude 10.52° 10.52° 10.52° 10.70° 10.69° XRF analyses Si02 70.32 74.08 70.19 73.82 73.67 Ti02 0.49 0.27 0.48 0.26 0.20 Al203 15.71 14.46 16.01 15.03 15.73 Fe203 4.00 2.23 3.48 1.82 1.38 MnO 0.18 0.05 0.08 0.07 0.06 M90 0.65 0.34 0.67 0.39 0.19 CaO 2.53 1.87 2.60 1.65 1.82 NaZO 2.04 2.59 2.61 3.00 3.12 K20 4.06 4.09 3.84 3.93 3.80 P205 0.03 0.02 0.03 0.02 0.01 Total 96.09 97.51 96.82 97.60 97.63 Rb 83 95 64 88 82 Sr 358 273 344 240 277 Zr 215 133 220 133 119 Laser ablation lCP-MS analyses Y 26.90 12.97 15.46 14.82 13.17 Nb 12.55 8.70 10.36 9.39 8.79 Ba 2002 1759 1 806 1 766 1 81 1 La 39.63 24.97 26.03 24.75 26.67 Ce 80.15 45.16 47.68 46.12 49.86 Pr 10.62 4.94 5.20 4.76 4.86 Nd 40.60 16.51 17.44 15.56 15.23 Sm 7.93 2.35 2.36 2.23 1.60 Eu 1.77 0.71 0.75 0.58 0.48 Tb 0.96 0.29 0.33 0.31 0.20 Dy 5.07 1.55 1.89 1.71 1.21 Ho 0.97 0.28 0.35 0.30 0.18 Er 2.89 0.71 0.79 0.75 0.33 Yb 3.06 1.38 1.39 1.56 1.07 Lu 0.49 0.19 0.19 0.24 0.13 Hi 5.48 2.64 2.98 2.80 2.23 Ta 0.83 0.57 0.58 0.59 0.58 Th 7.87 7.67 8.15 9.18 9.48 U 4.47 3.83 3.95 4.46 4.26 23 Table 1 cont. (Santa Fe) Sample 040708-2J 040706-28 040707-2A 040706-10A 040706-108 Location Longitude 85.390 85.17° 85.24° 85.18° 85.18° Latitude 10.69° 10.52° 10.57° 10.62° 10.62° XRF analyses Si02 73.52 72.89 70.69 70.25 70.17 Ti02 0.24 0.32 0.34 0.46 0.47 Al203 15.06 14.83 17.64 15.38 15.47 Fe203 1.89 2.50 2.77 3.27 3.39 MnO 0.07 0.07 0.09 0.09 0.09 M90 0.33 0.37 0.38 0.78 0.76 CaO 1.81 2.26 2.23 2.90 2.89 NaZO 3.14 2.63 2.31 3.10 3.02 K20 3.92 4.11 3.52 3.70 3.70 P205 0.01 0.02 0.02 0.05 0.04 Total 98.1 1 97.46 96.34 96.99 97.11 Rb 83 79 65 72 72 Sr 268 346 336 399 401 Zr 131 149 179 206 212 Laser ablation lCP-MS analyses Y 14.75 20.82 17.74 21.75 24.46 Nb 8.77 14.39 13.24 13.93 13.91 Ba 1 803 2647 1 707 1735 1742 La 27.66 39.08 33.28 30.40 29.91 Ce 46.31 73.00 60.64 59.65 58.35 Pr 5.23 7.52 7.19 7.02 6.90 Nd 16.70 24.03 24.09 24.82 25.46 Sm 2.21 3.02 3.70 4.87 5.17 Eu 0.57 0.85 1.03 1.32 1.44 Tb 0.30 0.40 0.43 0.72 0.80 Dy 1.63 2.25 2.38 3.59 3.97 Ho 0.27 0.38 0.43 0.72 0.84 Er 0.61 0.82 1.16 2.31 2.69 Yb 1.33 1.55 1.77 2.63 3.01 Lu 0.18 0.22 0.25 0.36 0.44 Hf 2.49 3.81 3.51 4.35 4.33 Ta 0.53 0.91 0.79 0.88 0.92 Th 8.62 12.86 9.12 7.22 7.02 U 3.97 6.53 3.85 3.75 3.85 24 Table 1 cont. (Santa Fe) Sample 040706-10C 040706-10D 040706-10E 040706-1 0F 040706-1 OG Location Longitude ' 85.18° 85.18° Latitude 10.62° 1 062° XRF analyses Si02 70.18 70.33 Ti02 0.48 0.49 Al203 15.36 15.19 Fe203 3.33 3.47 MnO . 0.09 0.09 M90 0.85 0.85 CaO 2.93 2.80 NaZO 3.20 2.96 K20 3.54 3.76 P205 0.04 0.04 Total 96.82 97.28 Rb 69 73 Sr 403 387 Zr 210 220 Laser ablation ICP-MS analyses Y 24.38 23.57 Nb 12.17 14.01 Ba 1651 1723 La 31.72 30.22 Ce 54.85 58.36 Pr 6.53 6.77 Nd 23.94 23.76 Sm 4.63 4.61 Eu 1.25 1.35 Tb 0.73 0.74 Dy 3.83 3.68 Ho 0.89 ' 0.77 Er 2.74 2.40 Yb 2.90 2.71 Lu 0.44 0.43 Hf 5.44 4.49 Ta 0.89 0.93 Th 8.58 7.20 U 3.06 3.79 85.18° 10.62° 70.18 0.46- 15.60 3.11 - . 0.08 0.80 2.93 2.96 3.84 - 0.04 96.39 74 408 21 1 22.68 13.42 1671 28.72 55.08 6.53 22.93 4.57 1.31 0.69 3.67 0.78 2.45 2.69 0.41 4.45 0.86 7.18 3.59 25 85.18° 10.62° 70.10 0.49 15.36 3.45 0.09 0.87 2.85 3.11 3.65 0.04 96.56 68 395 221 21.45 14.42 1734 29.39 59.25 6.64 23.19 4.62 1.34 0.71 3.59 0.79 2.57 2.73 0.43 4.74 0.95 7.15 3.75 85.18° 10.62° 69.61 0.49 15.52 3.63 0.09 0.90 3.04 3.18 3.48 0.05 97.31 69 425 202 27.67 11.56 1635 33.62 54.40 6.76 25.12 4.76 1.32 0.81 4.29 1.02 3.23 3.27 0.55 5.70 0.85 8.88 2.98 Table 1 cont. (Santa Fe) Sample 040706-10i 040706-10J 040706-10K 040706-10L 040706-4A Locaflon Longitude 85.18° 85.18° 85.18° 85.18° 85.15° Latitude 10.62° 10.62° 10.62° 10.62° 10.55° XRF analyses SiOZ 70.39 70.63 70.13 69.84 69.30 Ti02 0.48 0.48 0.50 0.48 0.48 A|203 15.35 14.94 15.02 15.57 15.96 Fe203 . ‘ 3.35 3.57 3.90 3.61 3.42 MnO 0.09 . 0.09 0.09 0.09 . 0.09 M90 0.74 0.84 0.89 0.76 0.82 CaO 2.85 2.68 2.75 2.95 3.10 NaZO 2.84 3.14 3.03 3.20 3.04 K20 3.85 3.57 3.65 3.46 3.69 P205 0.05 0.05 0.04 0.03 0.10 Total 97.47 97.18 97.10 97.29 97.68 Rb 73 72 70 67 72 Sr 41 1 374 385 421 432 Zr 216 220 219 213 210 Laser ablation lCP-MS analyses Y 22.17 20.90 23.36 23.15 21.99 Nb 14.16 13.84 12.89 12.78 12.31 Ba 1 859 1774 1759 1 701 1725 La 28.43 28.83 30.28 29.03 34.30 Ce 58.27 59.26 55.37 55.10 65.75 Pr 6.37 6.46 6.42 6.27 7.65 Nd 22.23 22.79 22.94 22.66 27.78 Sm 4.47 4.27 4.28 4.31 5.14 Eu 1.26 1.21 1.23 1.26 1.34 Tb 0.61 0.61 0.64 0.64 0.73 Dy 3.31 3.13 3.50 3.41 3.67 Ho 0.84 0.74 0.86 0.86 0.78 Er 2.52 2.28 2.51 2.53 2.42 Yb 2.68 2.50 2.62 2.72 2.59 Lu 0.44 0.38 0.42 0.42 0.39 Ht 4.54 4.62 5.43 5.06 4.45 Ta 0.91 0.92 0.90 0.86 0.78 Th 7.01 7.16 7.75 7.64 7.60 U 3.50 26 Table 1 cont. (Santa Fe) Sample 040706-4B 040706-4C 040706-4D 040706-4E 040706-4F Location Longitude 85.15° 85.15° 85.15° 85.15° 85.15° Latitude 10.55° 10.55° 10.55° 10.55° 10.55° XRF analyses Si02 68.95 67.93 69.73 69.16 68.34 Ti02 0.46 0.50 0.43 0.48 0.52 Al203 15.89 15.90 15.86 15.63 15.76 Fe203 3.55 . _ 4.29 3.27 3.78 4.17 MnO 0.10 0.09 0.07 0.08 0.10 . MgO 0.86 1.06 0.69 0.90 1.10 CaO 3.07 3.37 2.91 2.93 3.22 NazO 3.13 2.96 2.96 3.09 2.83 K20 3.86 3.77 3.99 3.83 3.84 P205 0.11 0.12 0.09 0.11 0.12 Total 97.30 97.91 97.28 97.33 97.46 Rb 73 71 79 75 74 Sr 436 465 429 41 1 437 Zr 204 188 198 204 199 Laser ablation ICP-MS analyses Y 22.06 24.37 22.01 21.99 20.98 Nb 12.34 11.58 12.48 12.78 12.37 Ba 1740 1668 1754 1699 1693 La 33.92 34.18 34.66 33.41 32.86 Ce 65.31 62.82 62.59 63.87 64.46 Pr 7.46 8.04 7.55 7.56 7.30 Nd 27.34 29.62 27.54 27.41 26.48 Sm 5.19 5.49 5.06 4.97 5.03 Eu 1.35 1.49 1.37 1.27 1.27 Tb 0.74 0.79 0.77 0.78 0.74 Dy 3.66 3.91 3.60 3.70 3.58 Ho 0.78 0.84 0.77 0.78 0.79 Er 2.53 2.70 2.45 2.51 2.40 Yb 2.66 2.74 2.66 2.67 2.58 Lu 0.39 0.42 0.39 0.41 0.39 Ht 4.27 3.91 4.55 4.60 4.06 Ta 0.78 0.70 0.86 0.86 0.79 Th 7.63 6.93 8.07 8.06 7.34 U 3.75 3.30 4.46 3.78 3.89 27 Table 1 cont. (Santa Fe) Sample 040706-1 A 040706-1 B 040706-1 C 040706-1 D 040706-1 E 040706-1 F 28 Location Longitude 85.17° 85.17° 85.17° 85.17° 85.17° 85.17° Latitude 10.52° 10.52° 10.52° 10.52° 10.52° 10.52° XRF analyses Si02 69.65 69.04 68.11 68.46 68.84 69.81 Ti02 0.46 0.48 0.50 0.49 0.51 0.51 Al203 16.15 16.43 17.99 17.90 16.89 16.29 . Fe203 3.42 3.62 3.76 3.56 3.69 3.68 MnO 0.08 0.09 0.08 - . 0.08 0.09 0.12 M90 0.76 0.75 0.58 0.44 0.65 0.48 CaO 2.91 3.08 2.78 2.76 2.88 2.59 NaZO 2.73 2.78 2.41 2.81 2.55 2.38 K20 3.81 3.68 3.76 3.46 3.86 4.10 P205 0.03 0.03 0.03 0.03 0.03 0.03 Total 96.58 96.96 96.1 1 96.69 96.40 96.17 Rb 81 77 76 74 81 84 Sr 420 448 404 413 416 375 Zr 199 1 93 21 1 209 200 206 Laser ablation lCP-MS analyses Y 25.31 24.46 37.89 32.49 23.90 28.07 Nb 12.08 12.21 13.18 13.23 12.38 13.49 Ba 1716 1714 1690 1719 1811 1879 La 32.90 33.29 53.80 40.52 34.52 39.04 Ce 58.83 61.09 65.82 68.94 63.71 74.13 ' Pr 7.47 7.56 13.38 9.53 7.65 9.07 Nd 27.38 28.35 49.79 34.63 27.88 33.23 Sm 5.35 5.52 9.16 6.62 5.07 6.22 Eu 1.51 1.66 2.33 1.88 1.48 1.60 Tb 0.78 0.77 1.14 0.94 0.70 0.87 Dy 4.19 4.20 6.28 5.17 3.88 4.44 Ho 0.91 0.91 1.31 1.16 0.80 0.94 Er 2.82 2.74 4.02 3.58 2.39 2.80 Yb 3.49 3.58 5.08 4.40 2.96 3.30 Lu 0.53 0.53 0.72 0.67 0.42 0.46 Hf 5.02 4.74 4.75 5.38 4.78 4.76 Ta 0.86 0.81 0.83 0.95 0.83 0.85 Th 8.26 7.83 8.38 9.19 8.24 8.18 U 3.85 3.82 4.15 4.58 3.67 3.75 Table 1 cont. (Santa Fe) Sample 040706-1G 040706-1H 040706-1i 040706-1L 040706-1M 040706-1N Location Longitude 85.17° 85.17° 85.17° 85.17° 85.17° 85.17° Latitude 10.52° 10.52° 10.52° 10.52° 10.52° 10.52° XRF analyses Si02 67.98 69.56 68.50 69.44 68.67 68.76 Ti02 0.51 0.50 0.51 0.47 0.48 0.48 Al203 17.34 16.09 16.49 16.13 17.71 16.66 Fe203 _ 3.76 3.69 4.01 3.49 3.67 3.70 MnO 0.15 0.10 0.11 0.09 0.07 0.10 M90 0.75 0.67 0.80 0.71 0.46 0.71 CaO 3.14 2.78 3.12 2.91 2.68 3.00 NaZO 2.83 2.55 2.88 2.93 2.60 2.74 K20 3.51 4.01 3.56 3.78 3.64 3.82 P205 0.03 0.03 0.03 0.03 0.03 0.03 Total 96.36 96.40 96.61 97.13 96.56 96.31 Rb 78 82 77 74 74 79 Sr 485 395 432 415 397 440 Zr 204 205 1 95 1 98 202 1 97 Laser ablation lCP-MS analyses Y 28.45 24.59 24.11 21.38 19.79 23.53 Nb 12.06 11.85 11.54 12.50 13.35 12.71 Ba 1895 1797 1740 1715 1709 1773 La 40.26 35.85 35.96 32.52 30.25 37.29 Ce 76.89 66.53 65.47 59.19 60.54 66.64 Pr 9.44 7.80 8.02 7.57 6.73 8.66 Nd 35.22 28.60 29.83 27.19 23.21 31.58 Sm 6.58 5.36 5.42 5.25 4.62 5.82 Eu 1.82 1.45 1.50 1.48 1.38 1.54 Tb 0.88 0.77 0.74 0.69 0.62 0.76 Dy 4.67 3.87 3.86 3.61 3.17 3.90 Ho 0.96 0.81 0.80 0.76 0.65 0.79 Er 2.79 2.44 2.48 2.26 2.14 2.32 Yb 3.31 3.01 2.97 2.56 2.54 2.90 Lu 0.46 0.43 0.42 0.42 0.42 0.40 Ht 4.81 4.71 4.58 4.96 5.04 4.58 Ta 0.80 0.81 0.76 0.78 0.86 0.78 Th 8.11 7.93 7.70 7.15 7.98 7.70 U 3.64 3.57 3.47 3.67 3.91 3.48 29 Table 1 cont. (Santa Fe) Sample 040707-4 040707-8A Location Longitude 85.23° Latitude 10.61 ° XRF analyses SiOz 69.45 Ti02 0.53 Al203 1 6.1 4 F9203 3.70 MnO 0.1 0 M90 0.78 CaO 3.01 NaZO 2.76 K20 3.49 P205 0.03 Total 96.97 Rb 65 Sr 389 Zr 206 85.33° 10.52° 73.69 0.23 15.78 1.84 0.06 0.23 1.61 2.17 4.38 0.01 96.60 85 227 125 Laser ablation lCP-MS analyses Y 25.04 Nb 10.44 Ba 1531 La 26.43 Ce 58.55 Pr 6.27 Nd 23.88 Sm 5.29 Eu 1 .49 Tb 0.74 Dy 4.23 Ho 0.92 Er 2.78 Yb 2.99 Lu 0.52 Hf 5.29 Ta 0.71 Th 6.55 U 3.59 16.58 9.28 1703 25.10 44.50 4.79 16.23 1 .99 0.53 0.28 1 .63 0.28 0.58 . 1.33 0.17 2.34 0.56 8.79 4.42 85.33° 10.52° 73.73 0.25 14.80 1.83 0.06 0.37 1.92 2.69 4.34 0.01 97.64 89 273 1 17 19.83 8.91 1688 26.34 44.00 5.17 17.35 2.39 0.66 0.34 1.97 0.37 0.88 1.53 0.21 2.26 0.49 8.08 3.99 30 85.33° 10.52° 73.42 0.24 15.14 1.70 0.06 0.30 1.90 3.22 4.03 0.01 97.84 274 114 18.63 9.27 1754 27.63 44.65 5.61 18.60 2.48 0.68 0.31 1.88 0.34 0.67 1.44 0.19 1.91 0.50 8.15 4.52 85.17° 10.52° 70.23 0.42 16.49 2.80. _ 0.06 0.36 2.61 2.95 4.04 0.03 96.00 85 194 381 19.44 12.62 1764 31.72 62.82 7.43 25.69 4.65 1.26 0.61 2.90 0.69 2.02 2.21 0.34 3.85 0.88 7.05 3.24 040707-8D 040707-8F 031021 -1a 031021 -1 d 85.17° 10.52° 69.04 0.47 17.46 3.18 0.08 - 0.39 2.65 2.86 3.84 0.03 96.20 76 1 94 397 20.80 12.78 1770 33.70 58.98 7.50 25.76 4.41 1 .35 0.64 3.06 0.64 2.14 2.26 0.36 4.17 0.87 7.42 3.33 Table 1 cont. (Santa Fe) Sample 031021-19 031021-1k-2 031022-1a 031022-1b 031022-10 031022-1d Location Longitude 85.17° 85.17° 85.24° 85.24° 85.24° 85.24° Latitude 10.52° 10.52° 10.61° 10.61° 10.61° 10.61° XRF analyses Si02 69.15 70.18 69.83 70.10 68.48 70.05 Ti02 0.46 0.48 0.47 0.48 0.55 0.44 Al203 16.26 15.77 15.68 15.10 15.91 15.76 Fe203 3.53 3.51 3.33 3.60 . 4.12 3.32 MnO 0.07 0.07 0.08 0.09 0.11 0.10 M90 0.69 0.63 0.86 1.02 0.95 0.65 CaO 2.73 2.32 2.98 2.89 3.16 2.89 Na20 2.76 2.73 3.08 3.00 3.20 3.10 K20 4.23 4.27 3.67 3.68 3.46 3.67 P205 0.1 1 0.03 0.03 0.03 0.06 0.03 Total 95.90 95.50 96.50 97.50 97.00 97.60 Rb 77 82 58 59 55 59 Sr 206 212 348 346 403 364 Zr 391 339 203 203 1 96 204 Laser ablation lCP-MS analyses Y 19.59 20.39 22.57 19.78 20.45 20.92 Nb 13.30 14.18 9.63 10.10 10.23 10.01 Ba 1762 1790 1479 1550 1531 1604 La 32.38 30.74 24.93 21.51 23.87 25.29 Ce 69.03 59.95 52.54 48.31 54.35 60.19 Pr 7.39 6.82 6.43 5.12 5.76 6.44 Nd 25.54 23.14 24.13 18.85 20.81 23.00 Sm 4.65 4.21 4.94 3.80 4.15 4.88 Eu 1.21 1.22 1.39 1.21 1.25 1.35 Tb 0.63 0.58 0.70 0.55 0.60 0.62 Dy 3.05 2.95 3.55 2.87 3.02 3.38 Ho 0.63 0.61 0.83 0.69 0.72 0.84 Er 2.15 1.93 2.40 2.11 2.42 2.40 Yb 2.11 2.14 2.54 2.35 2.42 2.55 Lu 0.39 0.41 0.42 0.35 0.36 0.40 Ht 4.34 4.14 3.82 3.84 3.62 4.11 Ta 0.86 0.95 0.63 0.69 0.64 0.66 Th 7.35 7.23 4.69 4.74 4.71 5.20 U 3.48 4.78 2.85 2.97 2.86 3.31 31 Table 1 cont. (Santa Fe) Sample 031022-1 e 031022-11 031022-1Q 031022-1h-1 031022-1h-2 Locafion Longitude 85.24° 85.24° 85.24° 85.24° 85.24° Latitude 10.61° 10.61° 10.61° 10.61° 10.61° XRF analyses Si02 71 .09 69.51 70.84 70.22 69.25 Ti02 0.42 0.48 0.46 0.45 0.47 Al203 15.07 15.46 15.39 15.31 16.16 Fe203 3.01 3.70 3.31 3.32 3.46 MnO 0.08 0.09 0.07 0.09 0.09 M90 0.72 0.93 0.55 0.85 0.73 CaO 2.69 3.03 2.58 2.95 3.05 NaZO 2.90 3.39 2.74 3.07 3.01 K20 3.96 3.36 4.03 3.71 3.70 P205 0.05 0.03 0.03 0.03 0.07 Total 96.70 96.90 96.70 97.40 96.70 Rb 62 56 65 61 58 Sr 324 366 332 349 382 Zr 201 203 21 1 202 201 Laser ablation lCP-MS analyses Y 23.49 19.18 19.70 21.73 21.72 Nb 9.71 9.59 10.65 10.43 9.67 Ba 1621 1492 1627 1556 1517 La 27.17 21.97 25.44 23.51 25.47 Ce 56.84 48.80 53.20 50.61 56.06 Pr 6.63 5.27 6.04 5.62 6.19 Nd 24.23 19.18 20.73 20.61 22.18 Sm 4.66 3.88 3.98 4.29 4.32 Eu 1.29 1.17 1.19 1.26 1.26 Tb 0.68 0.59 0.56 0.63 0.69 Dy 3.69 3.00 2.82 3.28 3.37 Ho 0.84 0.73 0.70 0.77 0.84 Er 2.56 2.16 2.09 2.41 2.41 Yb 2.75 2.27 2.19 2.48 2.60 Lu 0.42 0.37 0.36 0.38 0.38 Ht 4.04 3.66 3.98 3.98 3.67 Ta 0.68 0.66 0.76 0.66 0.73 Th 5.40 4.80 5.47 5.02 4.93 U 3.33 2.89 3.45 2.86 2.87 32 Table 1 cont. (Santa Fe) Sample 031022-1h-3 031022-1 i-1 031022-1 i-2 031022—1i-3 031022-1J-1 Location Longitude 85.24° 85.24° 85.24° 85.24° 85.24° Latitude 10.61° 10.61° 10.61° 10.61° 10.61° XRF analyses Si02 70.20 70.76 69.33 69.27 67.86 Ti02 0.46 0.48 0.50 0.49 0.57 Al203 15.72 14.97 15.98 16.26 16.72 Fe203 3.23 3.34 3.81 3.59 3.99 MnO 0.07 0.10 0.09 0.09 0.11 M90 0.76 0.89 0.70 0.64 1 .08 CaO 2.83 2.78 2.97 2.97 3.37 NaZO 3.01 2.65 2.82 2.91 3.01 K20 3.68 3.98 3.75 3.75 3.26 P205 0.03 0.05 0.04 0.03 0.03 Total 97.20 96.80 97.20 96.80 96.80 Rb 59 76 68 73 60 Sr 348 326 390 386 402 Zr 21 3 209 204 207 215 Laser ablation lCP-MS analyses Y 23.46 29.51 27.54 32.54 31.09 Nb 10.16 8.35 8.43 8.61 8.15 Ba 1 545 1535 1531 1528 1380 La 26.55 30.49 33.20 33.35 31 .09 Ce 50.74 56.38 55.00 56.90 54.03 Pr 6.93 7.01 7.26 7.91 6.99 Nd 24.74 27.43 28.59 31.38 27.40 Sm 4.87 5.94 5.27 6.25 5.42 Eu 1.36 1.37 1.37 1.47 1.45 Tb 0.73 0.82 0.78 0.93 0.84 Dy 3.58 4.66 4.10 5.06 4.54 Ho 0.84 1.08 0.94 1.20 1.04 Er 2.44 3.26 2.89 3.36 3.01 Yb 2.85 3.42 3.00 3.74 3.13 Lu 0.42 0.52 0.47 0.58 0.48 Hf 4.18 5.12 5.03 4.98 5.06 Ta 0.70 0.62 0.59 0.62 0.52 Th 5.15 6.16 6.16 6.48 5.74 U 3.06 2.58 2.22 2.59 2.29 33 Table 1 cont. (Santa Fe) Sample '031022-1J-2 031022-1J-3 010627-1 c 010627-6b 01 0627-60 Location Longitude 85.24° 85.24° 85.42° 85.45° 85.45° Latitude 10.61° 10.61° 10.71 ° 10.77° 10.77° XRF analyses Si02 70.13 69.38 69.06 71.35 70.84 Ti02 0.46 0.48 0.43 0.38 0.40 Al203 16.03 16.44 15.58 14.85 14.77 Fe203 3.42 3.49 4.27 2.87 3.20 MnO 0.12 0.12 0.12 0.09 0.08 M90 0.64 0.86 1.00 0.76 0.81 CaO 2.74 2.90 2.31 2.83 2.86 N320 2.62 2.75 3.00 2.86 3.13 K20 3.80 3.55 4.19 3.89 3.79 P205 0.03 0.03 0.04 0.10 0.10 Total 97.40 96.60 97.00 97.00 96.00 Rb 71 64 127 68 66 Sr 366 355 21 3 328 334 Zr 215 208 209 200 190 Laser ablation lCP-MS analyses Y 32.99 34.38 22.46 22.69 21.91 Nb 9.04 8.31 14.37 8.67 9.38 Ba 1623 1509 832 1495 1467 La 35.84 35.56 29.31 25.95 24.69 Ce 64.54 63.51 60.26 53.93 51.61 Pr 8.46 8.31 6.28 5.96 5.74 Nd 33.13 31.61 20.47 21.72 20.74 Sm 6.48 6.07 4.13 4.35 4.13 Eu 1.50 1.49 0.75 1.17 1.13 Tb 0.92 0.89 0.66 0.62 0.62 Dy 4.87 4.87 3.34 3.36 3.32 Ho 1.13 1.17 0.71 0.69 0.67 Er 3.29 3.34 2.15 2.03 1.96 Yb 3.44 3.41 3.71 3.27 3.24 Lu 0.55 0.57 0.45 0.38 0.37 Ht 5.45 5.08 4.77 4.33 4.23 Ta 0.62 0.57 0.98 0.61 0.61 Th 6.81 6.57 11.60 5.54 5.55 U 2.60 2.38 9.05 3.62 3.84 34 Table 1 cont. (Santa Fe) Sample 010627-6d 010627-6e 01 0627-6f 01 0627-69 01 0629-21 a Location Longitude 85.45° 85.45° 85.45° 85.45° 85.33° Latitude 10.77° 1 077° 10.77° 10.77° 10.52° XRF analyses Si02 68.13 71.15 70.81 69.95 72.68 Ti02 0.52 0.42 0.41 0.44 0.25 Al203 15.10 14.46 14.85 15.16 16.68 Fe203 4.49 3.35 3.14 3.41 1.88 MnO 0.10 0.09 0.08 0.09 0.07 M90 1 .40 0.89 0.80 0.89 0.28 CaO 3.99 2.80 3.02 3.29 1.64 N320 2.83 2.84 3.00 3.16 2.31 K20 3.32 3.89 3.78 3.50 4.17 P205 0.11 0.10 0.10 0.10 0.04 Total 97.00 97.00 97.00 98.00 97.00 Rb 63 67 66 63 86 Sr 382 31 6 355 377 223 Zr 177 194 188 194 134 Laser ablation lCP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Ht Ta Th U 20.81 9.44 1324 23.53 50.17 5.62 20.39 4.21 1 .20 0.59 3.16 0.66 1 .87 2.93 0.35 3.70 0.49 4.64 3.20 22.34 8.61 1461 24.80 51.73 5.81 20.91 4.29 1.16 0.64 3.48 0.71 2.10 3.31 0.41 4.27 0.64 5.52 3.65 21.75 8.62 1493 25.28 52.73 5.72 21.30 4.24 1.19 0.63 3.29 0.66 1.99 3.16 0.39 4.32 0.62 5.33 3.51 35 22.23 8.21 1438 24.32 51 .30 5.73 20.90 4.34 1.32 0.62 3.46 0.69 2.01 3.25 0.38 4.13 0.53 4.85 3.32 22.99 12.32 1759 28.87 50.57 6.09 20.81 3.93 0.99 0.57 3.07 0.71 2.08 2.88 0.42 2.69 0.85 8.79 5.77 Table 1 cont. (Santa Fe) Sample 010629-21 b 010629-21c 010629-21d 010629-21l 010629-21 9 Location Longitude 85.33° 85.33° 85.33° 85.33° 85.33° Latitude 10.52° 10.52° 10.52° 10.52° 10.52° XRF analyses Si02 73.48 73.10 72.61 73.06 73.95 Ti02 0.23 0.25 0.25 0.27 0.23 Al203 15.71 15.52 17.30 15.71 15.06 Fe203 1.74 1.88 2.03 2.22 1.85 MnO 0.07 0.08 0.07 0.10 0.06 MgO 0.28 0.35 0.28 0.42 0.28 CaO 1.61 1.82 1.46 1.54 1.61 NaZO 2.44 2.65 2.03 2.45 2.15 K20 4.40 4.30 3.92 4.19 4.77 P205 0.04 0.04 0.04 0.04 0.04 Total 97.00 97.00 97.00 96.00 97.00 Rb 94 92 84 87 108 Sr 228 259 199 259 227 Zr 129 129 140 157 145 Laser ablation lCP-MS analyses Y 18.25 16.42 23.40 24.85 15.22 Nb 11.96 10.99 11.83 15.35 11.25 Ba 1826 1794 1681 2315 1812 La 27.09 27.57 29.46 38.03 28.96 Ce 51.05 49.15 52.57 75.25 50.81 Pr 5.33 5.75 6.72 8.66 5.79 Nd 17.53 18.66 23.20 28.67 18.18 Sm 3.17 3.34 4.37 5.13 3.14 Eu 0.87 0.93 1.09 1.22 0.86 Tb 0.47 0.45 0.59 0.68 0.42 Dy 2.39 2.33 3.27 3.53 2.22 Ho 0.54 0.51 0.72 0.78 0.48 Er 1.68 1.62 2.14 2.39 1.49 Yb 2.28 2.29 2.93 3.31 2.31 Lu 0.33 0.31 0.44 0.45 0.29 Ht 2.57 2.62 2.80 3.88 2.72 Ta 0.85 0.72 0.85 1.04 0.80 Th 8.55 7.77 8.49 11.12 8.44 U 5.84 5.44 5.89 7.47 5.75 36 Table 1 cont. (Santa Fe) Sample 010629-21 h 010629-21 k 010629-21] 010629-21 L 010629-21 m Location Longitude 85.33° 85.33° 85.33° 85.33° 85.33° Latitude 10.52° 10.52° 10.52° 10.52° 10.52° XRF analyses Si02 73.77 71 .62 73.43 74.21 74.22 Ti02 0.23 0.29 0.24 0.25 0.23 Al203 15.25 17.33 15.23 14.24 15.17 Fe203 1.93 2.19 1.79 2.07 1.79 MnO - . . 0.06 0.07 0.07 0.09 0.06 M90 0.28 0.35 0.34 0.36 0.28 CaO 1.59 1.64 1.81 1.73 1.56 NaZO 2.08 2.18 2.67 2.53 2.33 K20 4.78 4.29 4.38 4.47 4.32 P205 0.04 0.04 0.04 0.04 0.04 Total 97.00 96.00 96.00 97.00 97.00 Rb 102 90 96 95 88 Sr 259 233 256 239 210 Zr 134 145 129 157 125 Laser ablation ICP-MS analyses Y 17.56 17.00 20.27 15.95 17.17 Nb 12.39 11.28 12.66 10.99 10.82 Ba 2017 1 795 1720 1 793 1 647 La 32.92 29.26 30.29 28.12 27.25 Ce 57.63 52.13 56.37 53.20 45.60 Pr 6.76 6.31 6.64 5.57 5.57 Nd 21.19 20.44 22.26 17.89 18.48 Sm 3.75 3.63 4.10 3.15 3.38 Eu 0.96 0.93 0.96 0.83 0.89 Tb 0.49 0.48 0.56 0.45 0.47 Dy 2.55 2.44 2.85 2.34 2.44 Ho 0.54 0.53 0.61 0.52 0.55 Er 1.80 1.66 1.82 1.57 1.71 Yb 2.46 2.25 2.73 2.21 2.32 Lu 0.35 0.32 0.37 0.30 0.33 Ht 2.96 2.56 2.81 2.91 2.68 Ta 0.86 0.79 0.86 0.77 0.79 Th 9.27 8.51 10.29 8.10 8.63 U 6.26 5.65 6.08 5.04 5.43 37 Table 1 cont. (Santa Fe) Sample 01 0629-21 n 010630-4a 010630-4b 01 0630-4c 01 0630-4d Location Longitude 85.33° 85.33° 85.33° 85.33° 85.33° Latitude 10.52° 10.57° 10.57° 10.57° 10.57° XRF analyses Si02 73.71 70.08 70.54 68.38 66.29 Ti02 0.23 0.45 0.49 0.50 0.56 AIZOS 15.39 15.83 15.45 17.54 19.27 Fe203 1.88 3.40 3.70 3.66 4.17 MnO 0.06 - . 0.07 0.08 0.08 0.09 M90 0.27 0.74 0.61 0.73 0.89 CaO 1.52 2.79 2.45 2.82 2.96 NaZO 1.96 2.89 2.59 2.80 2.75 K20 4.93 3.72 4.06 3.45 2.99 P205 0.04 0.03 0.04 0.03 0.03 Total 97.00 97.40 97.40 96.40 96.70 Rb 105 62 71 62 50 Sr 21 4 346 339 348 355 Zr 131 207 21 3 232 256 Laser ablation lCP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Hi Ta Th U 16.79 1 1 .57 1808 30.79 50.79 6.41 20.45 3.60 0.89 0.46 2.46 0.55 1 .69 2.44 0.35 2.71 0.82 8.98 5.88 23.69 10.32 1616 27.69 58.01 6.73 24.59 5.12 1 .31 0.66 3.65 0.74 2.32 2.43 0.39 4.14 0.63 5.27 3.78 22.56 1 1.28 1648 27.65 58.17 6.32 22.45 4.48 1.18 0.62 3.23 0.74 2.39 2.54 0.42 4.58 0.72 5.65 3.70 38 33.57 1 1.29 1565 42.45 65.33 10.82 38.25 7.38 1 .79 0.92 5.12 1.06 3.13 3.46 0.53 4.65 0.70 5.95 4.03 31.18 11.36 1412 28.88 47.90 6.19 22.82 4.66 1.21 0.73 4.15 0.90 2.74 3.17 0.52 6.21 0.77 7.40 3.35 Table 1 cont. (Santa Fe) Sample 010630-4e 010630-4t 01063043 010630-4h 010630-4i 010630-4J Location Longitude 85.33° 85.33° 85.33° 85.33° 85.33° 85.33° Latitude 10.57° 10.57° 10.57° 10.57° 10.57° 1 057° XFiF analyses Si02 67.87 67.60 68.84 68.13 67.95 71.43 Ti02 0.51 0.56 0.53 0.57 0.53 0.47 Al203 18.04 17.39 16.58 16.10 17.33 15.32 Fe203 3.85 4.17 3.68 4.47 4.16 3.63 MnO 0.07 - . 0.12 - 0.10 0.11 0.09 0.12 M90 0.82 0.84 0.96 1.12 0.70 0.70 CaO 2.91 3.17 3.12 3.12 2.96 2.69 NaZO 2.65 2.97 2.83 3.04 2.99 2.46 K20 3.25 3.15 3.30 3.30 3.25 3.15 P205 0.03 0.03 0.04 0.03 0.04 0.03 Total 96.60 97.20 97.50 97.90 97.00 97.70 Rb 56 61 58 58 55 54 Sr 356 397 372 366 399 338 Zr 219 224 215 210 211 198 Laser ablation ICP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Hf Ta Th U 22.53 1 1.02 1452 24.97 50.58 5.6 19.98 4.02 1.18 0.60 3.34 0.70 2.16 2.58 0.41 4.69 0.69 5.80 3.52 29.92 10.83 1322 28.81 58.57 7.65 27.52 5.79 1.50 0.81 4.34 0.88 2.82 3.72 0.49 4.62 0.59 5.44 3.95 30.46 10.39 1404 40.50 123.97 1 1.43 39.19 7.94 1.95 1.06 5.63 1 .07 3.12 3.36 0.50 4.74 0.63 5.33 3.84 39 39.51 9.34 1393 36.54 62.89 9.47 36.00 7.30 1.70 1 .02 5.66 1.13 3.43 3.67 0.57 4.60 0.58 5.35 3.1 1 32.84 10.06 1488 35.87 56.59 9.66 36.23 7.55 1.82 0.98 5.28 1.09 3.27 3.84 0.67 4.62 0.62 5.74 3.40 17.75 9.30 1309 19.67 48.00 4.66 16.89 3.65 1.06 0.49 2.64 0.55 1.71 1.90 0.32 4.14 0.58 4.91 3.23 Table 1 cont. (Santa Fe) Laser ablation lCP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Hf Ta Th U 23.89 13.27 1825 33.51 66.53 7.84 28.06 5.27 1.45 0.71 3.70 0.79 2.24 2.63 0.40 4.32 0.89 7.00 4.07 31 .26 13.16 1481 36.56 87.43 8.86 32.81 6.47 1 .56 0.83 4.38 0.94 2.75 3.07 0.50 4.27 0.91 6.92 3.31 25.09 12.36 1757 34.77 63.24 7.78 28.59 5.37 1.35 0.69 3.78 0.79 2.27 2.56 0.38 4.19 0.76 6.39 3.51 40 25.31 14.75 1890 35.46 71 .71 8.55 31.81 6.19 1 .57 0.76 4.10 0.85 2.49 2.88 0.45 4.74 1.02 8.03 4.44 Sample 990718-12a 990718-12b 990718-120 990718-12d 990718-12e Locafion Longitude 85.17° 85.17° 85.17° 85.17° 85.17° Latitude 10.52° 10.52° 10.52° 10.52° 10.52° XFiF analyses Si02 69.39 72.31 68.75 68.86 69.71 Ti02 0.49 0.45 0.53 0.50 0.45 Al203 15.90 17.24 16.32 17.22 16.25 . Fe203 3.80 3.52 4.13 3.75 3.32 MnO 0.09 0.06 0.10 0.08 0.08 M90 0.78 0.39 0.66 0.55 0.59 CaO 2.85 2.30 2.88 2.67 2.82 Na20 2.78 2.01 2.83 2.58 2.92 K20 3.86 1.68 3.74 3.75 3.79 P205 0.05 0.05 - 0.05 0.05 0.05 Total 97.46 96.09 97.29 97.18 97.51 Rb 80 34 80 78 81 Sr 408 345 41 9 394 407 Zr 197 186 189 204 196 20.92 13.19 1803 30.87 61.66 6.97 24.05 4.39 1 .22 0.57 3.17 0.67 2.02 2.32 0.35 4.30 0.90 6.84 4.04 Table 1 cont. (Santa Fe) Sample 99071 839— Location Longitude 85.17° Latitude 10.52° XRF analyses Si02 69.1 3 TiOz 0.48 Al203 16.1 1 F9203 3.77 MnO 0.07 M90 0.64 CaO 2.80 N320 3.05 K20 3.89 P205 0.05 Total 96.98 Rb 82 Sr 401 Zr 197 Laser ablation ICP-MS analyses Y 23.94 Nb 13.93 Ba 1815 La 35.87 Ce 64.72 Pr 8.34 Nd 29.87 Sm 5.70 Eu 1.45 Tb 0.69 Dy 3.82 Ho 0.76 Er 2.20 Yb 2.54 Lu 0.39 Hf 4.39 Ta 0.95 Th 6.80 U 4.52 Table 1 cont. (Pijije) Sample 031024-1A 031024-1 B 031 024-2A 031024-28 031 024-2C Location Longitude 85.54° 85.54° 85.54° 85.54° 85.54° Latitude 10.80° 10.80° 1 080° 10.80° 10.80° XRF analyses Si02 74.37 74.35 74.62 74.97 74.62 Ti02 0.23 0.22 0.20 0.20 0.19 Al203 14.70 14.35 14.41 14.01 14.48 Fe203 1.63 1.67 1.43 1.57 1.61 MnO 0.11 0.09 0.07 0.10 0.06 M90 0.32 0.29 0.28 0.20 0.29 CaO 1.74 1.79 1.67 1.67 1.99 Na20 2.61 2.77 2.92 2.81 2.95 K20 4.28 4.47 4.40 4.47 3.79 P205 0.01 0.01 0.01 0.01 0.01 Total 96.99 96.67 97.32 96.87 95.15 Rb 89 93 93 90 74 Sr 261 268 240 245 288 Zr 131 125 116 120 115 Laser ablation ICP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Ht Ta Th U 11.95 10.02 1803 24.22 46.56 4.46 14.54 2.58 0.81 0.42 1.88 0.44 1.49 1.67 0.26 3.16 0.91 8.95 4.36 11.55 9.78 1796 24.92 44.25 4.56 14.36 2.57 0.83 0.40 1.88 0.43 1.39 1.69 0.24 3.22 0.88 8.42 4.64 1 1.54 9.70 1721 24.79 43.32 4.54 14.35 0.42 0.42 0.38 1 .80 0.43 1 .42 1 .68 0.26 2.98 0.89 9.12 4.70 42 10.98 9.14 1761 24.40 44.30 4.36 13.77 0.40 0.40 0.39 1.72 0.39 1.32 1.59 0.25 2.92 0.88 8.97 4.43 10.45 8.47 1559 22.26 37.41 4.09 13.54 0.42 0.42 0.37 1 .70 0.43 1 .44 1 .58 0.23 2.85 0.81 8.09 4.00 Table 1 cont. (Pijije) Sample 031024-20 031024-2E 031024-2F 031024-2G 031024-2H Location Longitude 85.54° 85.54° 85.54° 85.54° 85.54° Latitude 10.80° 10.80° 10.80° 10.80° 10.80° XRF analyses Si02 74.06 73.88 74.23 73.94 74.27 Ti02 0.25 0.18 0.22 0.24 0.17 Al203 14.64 14.99 14.22 14.65 14.49 Fe203 1.91 1.37 1.76. . 1.81 1.31 MnO 0.08 0.08 0.08 0.08 0.11 M90 0.34 0.13 0.30 0.39 0.19 CaO 1.83 1.75 1.90 1.80 1.91 NaZO 2.56 3.11 2.96 2.63 3.28 K20 4.32 4.49 4.31 4.44 4.26 P205 0.01 0.01 - 0.01 0.01 0.01 Total 96.52 96.41 97.17 95.64 95.15 Rb 92 94 89 90 86 Sr 285 260 273 262 281 Zr 133 125 132 131 97 Laser ablation ICP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Hl Ta Th U 10.97 9.43 1847 24.97 42.55 4.56 14.65 0.40 0.40 0.40 1.74 0.40 1.37 1.62 0.26 3.36 0.91 8.75 4.25 11.31 9.93 1808 26.05 46.05 4.65 14.59 0.42 0.42 0.42 1.79 0.47 1.43 1.66 0.26 3.25 1.01 9.67 5.02 1 1.17 8.57 1680 23.67 41.55 4.23 13.65 0.40 0.40 0.38 1.69 0.41 1.31 1.58 0.25 3.08 0.76 8.19 3.99 43 1 1.06 9.25 1716 24.00 40.87 4.40 14.31 0.42 0.42 0.39 1.78 0.45 1 .44 1.68 0.26 3.25 0.89 8.54 4.35 11.07 9.22 1775 24.73 43.84 4.41 14.16 0.40 0.40 0.39 1.88 0.48 1.55 1.66 0.25 2.59 0.93 8.65 4.66 Table 1 cont. (Pijije) Sample . 040708-1 A 040708-1 B 040708-1 C 040708-1 D 040708-2A Location Longitude 85.39° 85.39° 85.39° 85.39° 85.39° Latitude 10.69° 10.69° 10.69° 10.69° 10.69° XRF analyses Si02 74.98 76.04 76.23 75.40 73.76 Ti02 0.24 0.22 0.20 0.23 0.24 Al203 15.29 14.38 14.41 14.40 15.09 Fe203 2.28 1.84 1.55 1.98 1.75 MnO 0.08 0.08 0.05 0.07 0.07 M90 0.10 0.08 0.05 0.10 0.33 CaO 1.73 1.04 1.10 1.28 1.80 Na20 2.60 2.27 2.38 2.65 2.98 K20 2.69 4.04 4.02 3.87 3.98 P205 0.01 0.01 . 0.01 0.01 0.01 Total 98.20 98.44 98.27 98.45 97.44 Rb 65 103 103 96 86 Sr 304 201 208 229 264 Zr 152 137 131 151 131 Laser ablation ICP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Hi Ta Th U 10.98 8.73 1686 21 .60 39.41 4.12 13.55 2.46 0.99 0.33 1.73 0.47 1.45 1.44 0.23 3.18 0.77 5.57 12.55 8.76 1923 25.56 39.75 4.70 15.29 2.87 0.94 0.42 1.91 0.56 1.72 1.84 0.30 3.83 1.02 9.25 10.59 9.40 191 1 23.49 38.94 4.27 13.70 2.44 0.83 0.34 1.69 0.47 1.38 1.48 0.23 3.08 1.14 8.26 12.50 10.15 1967 25.99 44.43 4.73 15.04 2.77 0.92 0.37 1 .90 0.50 1 .47 1 .63 0.27 2.97 0.88 6.87 13.87 9.44 1759 26.48 48.71 5.24 17.62 3.54 0.94 0.48 2.40 0.48 1.58 2.23 0.37 3.89 0.85 9.33 4.32 Table 1 cont. (Pijije) Sample 040708-28 040708-2C 040708-2D 040708-2F 04070826 Location Longitude 85.39° 85.39° 85.39° 85.39° 85.39° Latitude 10.69° 10.69° 10.69° 10.69° 10.69° XRF analyses Si02 73.88 73.91 73.03 73.03 72.46 Ti02 0.19 0.21 0.29 0.28 0.25 Al203 15.54 14.92 15.30 15.14 16.36 Fe203 1.46 1.61 2.07 1.86 1.74 . MnO 0.06 0.07 0.07 0.07 0.07 M90 0.12 0.27 0.46 0.43 0.34 CaO 1.61 1.71 1.92 1.92 2.12 Na20 2.78 2.95 3.08 3.26 3.25 K20 4.35 4.33 3.76 4.00 3.41 P205 0.01 0.01 0.01 0.01 0.01 Total 97.51 98.04 97.90 97.81 97.81 Rb 97 96 87 92 74 Sr 259 262 278 283 310 Zr 132 126 151 141 147 Laser ablation lCP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Ht Ta Th U 14.34 1 1 .72 1927 28.86 55.64 5.52 17.98 3.28 0.87 0.44 2.19 0.57 1.76 1.90 0.30 3.39 1.15 9.55 12.89 10.41 1894 26.64 51 .78 5.03 16.10 2.98 0.86 0.40 2.01 0.53 1 .55 1.90 0.30 2.96 0.99 8.24 14.87 10.66 1803 28.15 46.84 5.40 17.38 3.06 0.86 0.42 2.29 0.54 1.65 1.78 0.29 3.36 0.90 8.05 45 13.78 10.41 1950 28.06 50.87 5.32 17.20 2.97 0.85 0.42 2.05 0.54 1.61 1.81 0.29 3.27 0.93 7.82 14.57 10.87 1837 26.83 49.90 5.37 17.68 3.42 0.93 0.44 2.33 0.60 1.78 1.96 0.32 3.39 1.00 8.20 Table 1 cont. (Pijije) Sample 040708-2i 040708-6B 040708-6C 040708-6E 040706-3C Location Longitude 85.39° 85.38° 85.38° 85.38° 85.17° Latitude 10.69° 10.70° 10.70° 10.70° 10.52° XRF analyses Si02 73.13 72.63 73.21 73.57 70.28 Ti02 0.24 0.27 0.23 0.19 0.35 Al203 16.12 16.83 15.70 15.70 18.86 Fe203 1.80 1.67 1.66 1.61 2.97 MnO 0.09 0.08 0.07 0.07 0.06 M90 0.23 0.41 0.36 0.20 0.45 CaO 1.89 1.64 1.93 1.82 1.43 NaQO 2.96 2.51 3.09 2.86 2.26 K20 3.54 3.97 3.74 3.96 3.32 P205 0.01 0.01 0.01 0.01 0.02 Total 97.34 97.76 98.69 98.79 96.49 Rb 72 84 79 81 80 Sr 279 247 280 269 215 Zr 137 143 126 132 145 Laser ablation ICP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Ht Ta Th U 14.44 10.74 1742 27.31 49.90 5.08 16.58 3.15 0.89 0.44 2.30 0.62 1 .80 2.05 0.33 3.60 0.96 9.27 16.63 10.78 1847 24.51 52.42 4.87 16.38 3.52 0.97 0.50 2.55 0.74 2.34 2.67 0.45 3.56 1.04 9.58 13.50 10.48 1874 24.40 48.26 4.75 15.10 2.90 0.89 0.42 2.13 0.57 1.73 2.03 0.32 2.90 0.96 8.07 46 14.04 10.96 1882 24.48 51 .65 4.69 15.23 2.90 0.91 0.41 2.14 0.59 1.74 2.01 0.32 2.98 1.07 8.73 16.80 10.64 1844 26.89 47.65 5.16 17.58 3.35 0.88 0.49 2.50 0.52 1.76 2.23 0.35 3.87 0.97 9.82 4.39 Table 1 cont. (Pijije) Sample 040706-3D 04070636 031021 -1 b 031021 -1 c 031021-1e 031021-1i* Location Longitude 85.17° 85.17° 85.17° 85.17° 85.17° 85.17° Latitude 10.52° 10.52° 10.52° 10.52° 10.52° 10.52° XRF analyses Si02 72.94 71 .27 71 .09 72.42 71.22 70.07 Ti02 0.23 0.33 0.25' 0.21 0.23 0.22 Al203 15.49 16.75 15.08 14.49 13.86 14.70 Fe203 1.86 2.72 1.78 1.50 1.66 1.60 MnO 0.13 0.08 » . 0.05 0.05 0.05 0.05 M90 0.32 0.63 0.34 0.23 0.29 0.17 CaO 2.09 1.79 1.58 1.93 1.51 1.46 NazO 3.13 2.72 2.58 3.05 2.45 2.48 K20 3.80 3.70 4.15 3.95 4.72 4.19 P205 0.01 0.02 . 0.02 0.01 0.01 0.01 Total 97.88 96.84 96.92 97.84 96.00 94.95 Rb 78 91 102 93 105 97 Sr 302 247 242 295 238 233 Zr 125 165 127 115 131 120 Laser ablation ICP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Hi Ta , Th U 15.51 8.24 1876 28.00 46.79 5.21 17.91 3.31 0.99 0.48 2.38 0.51 1.75 2.16 0.32 3.46 0.74 8.89 3.95 24.37 10.21 1820 35.25 52.78 7.40 26.82 4.89 1.18 0.73 3.74 0.80 2.39 3.04 0.45 4.41 0.90 10.42 4.22 13.88 10.39 1860 27.99 46.21 5.19 16.52 2.86 0.85 0.36 1 .82 0.46 1 .45 1 .57 0.27 2.93 1.04 8.00 3.88 47 10.23 9.55 1754 23.97 45.13 4.60 14.09 2.39 0.91 0.35 1.56 0.41 1.27 1.36 0.24 2.51 0.85 6.81 4.01 12.97 10.02 1865 25.29 45.13 4.83 15.80 2.64 0.71 0.40 1.74 0.40 1 .38 1.59 0.29 3.14 0.95 8.75 3.95 13.58 9.68 1697 26.94 45.89 5.14 16.38 2.81 0.84 0.42 1.95 0.44 1.44 1.63 0.35 3.19 0.88 9.44 5.21 Table 1 cont. (Pijije) Sample 031021 -1J 031021 -1 k-1 031021-1k-3* 031021 -1 H 031021-1I-2" Location Longitude 85.17° 85.17° 85.17° 85.17° 85.17° Latitude 10.52° 10.52° 10.52° 10.52° 10.52° XRF analyses Si02 70.29 71.23 69.54 71.52 77.79 Ti02 0.26 0.21 0.27 0.23 0.26 Al203 14.70 14.44 14.61 13.69 11.46 Fe203 1.98 1.51 2.11 1.64 1.48 MnO 0.04 0.06 0.07 0.06 0.04 M90 0.26 0.22 0.39 0.31 0.31 CaO 1.80 1.70 1.57 1.41 0.93 NaZO 2.63 2.80 2.97 2.81 1.36 K20 4.05 4.26 3.95 4.35 1.73 P205 0.02 0.01 . 0.01 0.01 0.02 Total 96.03 96.44 95.49 96.03 95.38 Rb 99 98 94 103 59 Sr 286 266 236 212 160 Zr 129 1 19 146 126 95 Laser ablation lCP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Ht Ta Th U 14.09 9.63 1752 26.00 48.77 5.40 16.43 2.91 1.09 0.49 1.91 0.43 1.40 1.54 0.31 3.03 0.91 8.17 4.40 12.25 9.99 1823 25.33 47.82 5.21 15.26 2.76 1.14 0.48 1.70 0.43 1.33 1.41 0.32 2.68 0.90 7.79 4.65 12.04 10.93 181 1 23.93 44.58 4.55 13.78 2.41 0.83 0.35 1.63 0.35 1.32 1.42 0.28 3.16 0.99 8.59 5.26 48 12.98 10.78 1823 26.08 47.57 5.27 16.00 2.94 0.91 0.42 1 .86 0.47 1.59 1.57 0.34 2.86 0.97 8.02 4.89 9.74 9.45 1582 16.18 33.76 3.77 11.34 2.20 0.93 0.42 1.57 0.38 1.15 1.13 0.29 2.36 1.09 5.38 6.71 Table 1 cont. (Pijije) Sample 010627-1a 010627-1b 010627-1d 010627-3d 010629-1b 010629-10 Location Longitude 35.42° 85.42° 35.42° 35.42° 85.35° 85.35° Latitude 10.71° 10.71° 10.71° 10.71° 10.54° 10.54° XRF analyses 3102 73.97 72.00 74.73 73.74 74.53 74.62 Tio2 0.24 0.32 0.21 0.23 0.28 0.26 Al203 15.09 15.31 14.37 15.72 13.97 13.87 Fe203 1.81 2.31 1.61 1.65 1.75 1.73 MnO 0.09 0.07 0.07 0.08 0.08 ~ 0.07 M90 0.35 0.55 0.27 0.27 0.52 0.46 CaO 1.67 1.92 1.58 1.58 1.71 1.75 Nazo 2.32 2.35 2.45 2.37 2.82 2.33 K20 4.42 4.13 4.66 4.32 4.29 4.27 P205 0.04 0.05 0.05 0.04 0.05 0.04 Total 97.00 98.00 98.00 97.00 98.00 98.00 Rb 94 125 102 93 99 115 Sr 236 289 234 227 233 247 Zr 136 154 121 133 133 133 Laser ablation ICP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Hf Ta Th U 13.78 10.21 1831 25.77 51.08 4.70 14.76 2.60 0.77 0.42 2.01 0.40 1.29 2.71 0.28 3.02 0.98 8.74 7.42 13.90 10.18 1733 23.88 44.16 4.39 13.74 2.62 0.89 0.45 2.09 0.41 1 .36 2.70 0.30 3.69 0.84 8.10 5.71 10.94 9.49 1872 25.63 51.92 4.50 13.48 2.34 0.72 0.40 1.69 0.33 1.11 2.48 0.24 3.01 1.00 8.68 6.08 49 15.07 10.04 1709 31.19 56.47 5.55 17.28 3.12 0.78 0.50 2.33 0.47 1 .47 3.15 0.35 3.31 1 .00 9.92 5.92 17.30 10.89 1942 29.62 48.46 5.84 18.56 3.35 0.83 0.48 2.37 0.51 1.59 2.51 0.32 3.02 0.98 8.29 6.19 16.89 10.11 1908 28.74 44.97 5.66 18.31 3.33 0.88 0.48 2.44 0.55 1 .57 2.56 0.34 3.06 0.92 7.98 6.69 Table 1 cont. (Pijije) Sample 01 0629-1 d 99071 9-5b 990720-1 a 990720-1 b 990720-1c 990720-1 e Location Longitude 85.35° 85.37° 85.57° 85.57° 85.57° 85.57° Latitude 10.54° 10.69° 10.85° 10.85° 10.85° 10.85° XFiF analyses Si02 74.75 74.45 70.73 73.75 72.05 74.49 Ti02 0.24 0.22 0.28 0.25 0.26 0.20 Al203 14.47 14.19 17.55 14.75 17.15 14.20 Fe203 1.48 1.66. 2.27 2.45 2.66 2.03 MnO 0.06 0.07 0.33 0.10 0.07 0.08 M90 0.39 0.30 0.40 0.37 0.28 0.25 030 1 .80 1.82 1.90 1.54 1.47 1.74 Na20 2.85 2.88 2.38 2.17 1.98 2.45 K20 3.92 4.37 4.11 4.58 4.03 4.54 P205 0.04 0.04 0.04 0.04 0.04 0.04 Total 97.00 97.40 93.10 93.00 95.90 96.80 Rb 94 91 103 108 84 96 Sr 261 264 276 221 1 98 239 Zr 127 128 153 132 149 142 Laser ablation ICP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Ht Ta Th U 12.14 1 1 .36 1954 25.46 42.01 4.55 13.88 2.44 0.72 0.37 1 .69 0.36 1.17 2.01 0.22 2.90 1.02 7.96 6.99 12.52 8.66 1778 25.33 46.52 4.47 14.24 2.51 0.73 0.37 1 .91 0.34 1.1 1 2.33 0.28 3.26 0.86 7.97 4.78 18.28 11.04 2550 27.84 51.33 5.26 17.36 3.17 0.99 0.44 2.43 0.51 1 .52 2.74 0.33 3.73 1.08 10.08 5.32 50 14.02 9.76 1822 25.57 45.09 4.55 14.90 2.66 0.76 0.35 1 .94 0.38 1.24 2.27 0.27 3.33 0.96 8.93 5.70 15.37 11.48 1661 24.52 45.30 4.48 14.53 2.65 0.72 0.39 2.04 0.43 1 .31 2.43 0.32 3.63 1.19 10.32 5.78 12.93 9.00 1684 25.04 44.07 4.63 14.99 2.70 0.78 0.35 1.77 0.36 1.16 2.15 0.27 3.17 0.88 7.82 5.03 Table 1 cont. (Pijije) Sample 99071 953 99071 9-5b Location Longitude 85.37° 85.37° Latitude 1 069° 10.69° XRF analyses Si02 74.03 74.45 Ti02 0.22 0.22 Al203 14.57 14.19 Fe203 1 .47 1 .66 MnO 0.06 0.07 M90 0.30 0.30 CaO 1 .94 1 .82 Na20 3.47 2.88 K20 3.90 4.37 P205 0.04 0.04 Total 96.90 97.40 Rb 88 91 Sr 286 264 Zr 1 1 9 128 Laser ablation lCP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Ht Ta Th U 1 1 .82 8.75 1832 26.15 46.77 4.56 14.10 2.56 0.81 0.35 1.65 0.34 1 .04 2.17 0.24 2.92 0.83 7.40 5.00 12.52 8.66 1778 25.33 46.52 4.47 14.24 2.51 0.73 0.37 1.91 0.34 1.1 1 2.33 0.28 3.26 0.86 7.97 4.78 51 Table 1 cont. (Salitral East) Sample 990717-4a 990717-4d 990717-4e 990717-41 990717-49 990717-4h Location Longitude 85.17° 85.17° 85.17° 85.17° 85.17° 85.17° Latitude 10.61° 10.61° 10.61° 10.61° 10.61° 10.61° XRF analyses 5102 72.36 72.29 71 .55 73.58 73.20 72.77 Tio2 0.34 0.36 0.37 0.32 0.31 0.34 Al203 14.75 15.42 16.38 14.52 15.10 14.82 Fe203 2.84 2.79 2.78 2.39 2.23 2.48 MnO 0.06 0.06 ~ 0.08 0.08 0.06 0.07 M90 0.57 0.38 0.37 0.38 0.35 0.45 C60 2.39 2.17 2.13 1.95 2.01 2.26 Na20 2.70 2.36 2.40 ‘ 2.41 2.67 2.57 K20 3.96 4.15 3.91 4.36 4.06 4.22 13205 0.02 0.02 0.02 0.02 0.02 0.02 Total 97.40 97.00 96.90 98.00 97.40 97.00 Rb 80 77 74 80 78 78 Sr 349 326 330 312 317 344 Zr 159 165 180 154 151 156 Laser ablation lCP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Ht Ta Th U 13.82 12.28 1701 24.04 46.75 4.75 15.7 2.9 0.91 0.38 1.85 0.49 1.47 1.67 0.28 3 0.91 6.77 2.97 26.01 1 1.25 1625 31.85 42.41 7.27 25.82 3.94 0.91 0.52 3.06 0.78 2.28 2.54 0.46 4.01 0.82 8.74 2.64 20.35 14.51 1802 29.25 53.53 6.5 23.75 4.49 1.22 0.53 2.7 0.69 2.24 2.41 0.46 3.83 1.12 8.54 3.99 52 15.7 12.99 1852 28.42 57.96 5.73 18.76 3.15 0.87 0.37 2.09 0.53 1 .68 1.78 0.34 3.37 7.85 3.46 18.28 12.28 1790 28.46 48.8 6.73 22.08 3.36 0.95 0.41 2.28 0.57 1.78 2.03 0.35 3.4 1.02 3.4 15.96 11.76 1804 28.37 52.62 5.67 19.6 3.47 0.41 2.17 0.55 1.62 1.86 0.31 3.4 0.96 7.36 3.06 Table 1 cont. (Salitral East) Sample 990717-4i 990717-4J 990717-4k 010630-23 010630-2b 01 063020 Location Longitude 85.17° 85.17° 85.17° 85.34° 85.34° 85.34° Latitude 10.61° 10.61° 10.61° 10.71° 10.71° 10.71° XRF analyses SiOZ 69.84 72.78 73.36 73.76 73.78 74.16 Ti02 0.39 0.37 0.34 0.41 0.41 0.39 Al203 17.54 14.92 14.20 14.86 14.98 14.63 Fe203 . 3.07 2.74 2.50 2.86 2.85 2.69 MnO 0.09 0.07 0.06 0.08 . 0.09 0.08 M90 0.47 0.48 0.46 0.59 0.57 0.52 CaO 2.49 2.09 2.10 1.95 2.06 1.89 NaQO 2.64 2.48 2.61 1.84 1.58 1.77 K20 3.45 4.05 4.35 3.60 3.62 3.83 P205 0.02 0.02 0.02 0.05 0.05 0.05 Total 96.50 97.10 97.70 96.00 96.00 96.00 Rb 57 75 83 77 81 82 Sr 378 31 1 321 273 281 265 Zr 189 161 148 222 225 212 Laser ablation ICP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Ht Ta Th U 16.48 14.1 1689 30.31 61 .26 6.65 23.01 4.16 1.28 0.49 2.49 0.64 1.97 2.31 0.42 3.93 1.06 8.54 3.48 16.12 12.86 1823 27.99 59.64 5.72 19.13 3.48 0.99 0.43 2.17 0.56 1 .71 1 .96 0.37 3.42 1 .02 7.77 3.35 15.39 10.13 1712 28.03 45.67 4.84 17 2.92 0.77 0.35 2.12 0.51 1.6 1.8 0.32 3.62 0.8 8.21 2.47 53 21.47 10.58 1832 30.78 55.35 6.28 21 .94 4.02 1.12 0.59 3.1 0.64 1.95 3.18 0.38 4.85 0.86 7.2 4.63 21.3 10.94 1944 31.93 57.46 6.55 22.44 4.12 1.14 0.57 3.01 0.62 1.88 3.2 0.38 4.87 0.93 7.62 4.84 20.6 9.69 1740 29.07 51.78 6.11 21.2 3.92 1.1 0.57 2.94 0.63 1.85 3.16 0.37 4.66 0.76 6.69 4.09 Table 1 cont. (Salitral East) Sample 01 0630-2d 01 0630-2e 010630-21 01 0630-29 01 0630-2h Location Longitude 85.34° 85.34° 85.34° 85.34° 85.34° Latitude 10.71° 10.71° 10.71° 10.71° 10.71° XRF analyses Si02 72.80 72.12 72.16 73.08 72.15 Ti02 0.42 0.48 0.45 0.42 0.46 A|203 15.65 16.08 15.13 15.55 16.98 Fe203 2.95 3.62 3.55 2.90 3.33 MnO 0.08 . . 0.08 0.09 0.09 0.08 . MgO 0.58 0.55 0.67 0.59 0.48 C80 2.17 2.08 2.37 2.11 1.96 N320 1.70 1.53 1.94 1.61 1.17 K20 3.59 3.38 3.56 3.62 3.34 P205 0.05 0.07 - 0.06 0.05 0.05 Total 94.00 95.00 95.00 94.00 94.00 Flb 78 73 73 76 76 Sr 309 282 317 295 282 Zr 222 216 206 224 230 Laser ablation ICP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Hf Ta Th U 20.24 10.38 1909 29.58 54.93 6.18 21.74 4.04 1.21 0.57 2.96 0.61 1.76 3.07 0.35 4.87 0.81 6.87 4.5 24.77 10.15 181 1 33.66 54.72 6.9 24.15 4.79 1 .39 0.66 3.54 0.72 2.16 3.69 0.45 4.71 0.88 6.76 4.26 24.24 10.91 2054 31.85 57.8 7.04 25.55 5.13 1.39 0.67 3.56 0.74 2.18 3.48 0.42 4.92 0.93 7.54 4.49 54 19.53 9.66 1773 28.25 53.4 5.8 19.93 3.79 1.16 0.55 2.93 0.58 1.71 0.35 4.4 0.74 6.29 4.34 21.34 10.55 1838 29.75 57.02 6.38 22.1 1 4.12 1.17 0.6 3.12 0.64 1.89 3.14 0.37 4.72 0.84 7.09 4.48 Table 1 cont. (Salitral East) Sample 01 0630-3a 010630-3d 01 0630-3e 01 0630-3t 01 0630-39"_ Location Longitude 85.30° 85.30° 85.30° 85.30° 85.30° Latitude 10.66° 10.66° 10.66° 10.66° 10.66° XRF analyses Si02 73.61 73.61 72.79 72.22 73.61 Ti02 0.38 0.41 0.41 0.41 0.40 A|203 14.72 14.82 15.08 16.29 14.90 Fe203 2.63 2.83 3.00 2.86 3.01 MnO 0.12 0.09 - 0.14 0.08 0.09 M90 0.55 0.55 0.53 0.48 0.44 CaO 2.15 2.22 2.28 2.30 1.99 NaZO 2.03 1.62 2.08 1.95 1.55 K20 3.76 3.81 3.64 3.36 3.97 P205 0.04 0.04 . 0.05 0.05 0.04 Total 96.20 96.30 95.90 94.50 95.60 Rb 81 83 76 76 93 Sr 301 313 31 8 322 306 Zr 231 228 222 230 216 Laser ablation lCP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Ht Ta Th U 17.92 10.82 1914 29.28 65.65 6.37 21.76 4.03 1.14 0.54 2.71 0.66 2.01 2.13 0.36 4.57 0.84 6.76 3.34 17.82 10.90 1853 28.25 59.79 6.39 21.61 4.07 1.16 0.53 2.63 0.66 1.88 2.19 0.34 4.42 0.81 6.51 3.29 18.94 11.05 1863 28.04 71.49 6.21 20.98 4.20 1.18 0.57 2.80 0.70 2.10 2.42 0.38 4.36 0.83 6.43 3.56 55 21.32 10.92 1784 29.47 61.46 6.80 23.51 4.70 1.35 0.64 3.29 0.81 2.35 2.58 0.42 4.51 0.87 6.70 3.48 21.20 11.40 1960 32.23 69.41 7.39 25.45 4.83 1.41 0.64 3.09 0.79 2.29 2.44 0.40 4.37 0.95 7.27 4.12 Table 1 cont. (Salitral East) Sample 01 0630-3h 040706-5B 040706-5C 040706-5E 040706-6A Location Longitude 85.30° 85.15° 85.15° 85.15° 85.15° Latitude 10.66° 10.56° 10.56° 10.56° 10.56° XRF analyses Si02 72.51 73.64 73.47 73.01 73.54 Ti02 0.42 0.29 0.33 0.32 0.33 Al203 15.73 14.45 14.19 14.59 14.36 Fe203 _ 3.09 2.25 2.41 2.63 2.60 MnO 0.08 0.07 0.08 0.08 0.08 M90 0.49 0.35 0.55 0.41 0.48 C30 2.27 2.22 2.26 2.27 2.03 N320 1.83 2.60 2.60 2.48 2.10 K20 3.53 4.1 1 4.08 4.18 4.45 P205 0.04 0.02 0.02 0.02 0.02 Total 95.20 96.90 97.32 97.05 97.44 Rb 86 80 83 82 89 Sr 331 346 330 343 314 Zr 227 143 155 153 154 Laser ablation lCP-MS analyses Y 18.09 13.66 15.71 17.39 17.06 Nb 12.60 11.29 12.54 11.24 12.02 Ba 1862 1820 1792 1785 1840 La 29.21 27.69 28.78 29.93 28.93 Ce 66.19 48.87 50.85 52.19 52.89 Pr 6.58 5.44 5.61 6.16 5.92 Nd 22.10 17.68 18.74 21.12 19.98 Sm 4.23 3.43 3.47 4.26 4.00 Eu 1.26 1.06 1.02 1.19 1.14 Tb 0.60 0.46 0.53 0.54 0.54 Dy 2.68 2.28 2.41 2.78 2.78 Ho 0.69 0.47 0.50 0.57 0.58 Er 2.08 1.57 1.62 1.87 1.88 Yb 2.22 2.19 1.91 2.44 2.41 Lu 0.36 0.35 0.30 0.40 0.41 Ht 4.70 3.97 3.43 4.15 4.32 Ta 0.93 0.87 0.96 0.86 0.92 Th 7.15 7.83 7.46 7.99 8.26 U 4.20 3.62 3.76 3.67 3.85 56 Table 1 cont. (Salitral East) Sample 040706-7A 040706-7B 040706-7C 040706-7D 040706-7E Location Longitude 85.15° 85.15° 85.15° 85.15° 85.15° Latitude 10.56° 10.56° 10.56° 10.56° 10.56° XRF analyses Si02 73.44 73.21 72.66 73.24 73.33 Ti02 0.32 0.32 0.35 0.31 0.30 Al203 14.20 14.37 14.52 14.44 14.51 Fe203 2.49 2.53 2.84 2.48 2.28 MnO 0.08 0.09 0.09 0.07 0.07 . . MgO 0.55 0.52 0.59 0.47 0.39 CaO 2.24 2.22 2.31 2.22 2.25 Na20 2.55 2.56 2.29 2.30 2.45 K20 4.12 4.15 4.33 4.45 4.42 P205 0.02 0.02 0.02 0.02 0.02 Total 98.10 97.50 97.61 97.83 97.55 Rb 83 76 86 83 83 Sr 334 328 343 340 349 Zr 150 150 168 147 151 Laser ablation ICP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Ht Ta Th U 16.13 12.22 1805 27.92 50.73 5.64 18.50 3.31 1.00 0.53 2.47 0.50 1.60 2.00 0.30 3.37 0.94 7.58 3.77 16.66 12.89 1854 28.57 52.32 5.74 19.09 3.58 1.08 0.52 2.49 0.56 1.77 2.16 0.33 3.38 1.02 7.64 4.23 17.77 12.59 1894 29.88 55.33 6.17 20.61 3.94 1.13 0.58 2.78 0.55 1.82 2.23 0.34 3.67 0.93 7.65 3.91 57 15.44 12.61 1870 27.98 52.53 5.58 18.12 3.26 1.02 0.51 2.41 0.54 1.73 2.07 0.31 3.40 1.05 7.92 4.39 14.34 12.56 1841 26.66 51.27 5.24 17.10 3.07 0.98 0.49 2.27 0.52 1.68 1.88 0.31 3.39 1.05 7.57 4.29 Table 1 cont. (Salitral East) Sayle 040706-7F 040706-7G 040706-7H 040706-7i 040706-7J Location Longitude 85.15° 85.15° 85.15° 85.15° 85.15° Latitude 10.56° 10.56° 10.56° 10.56° 10.56° XRF analyses Si02 73.31 73.38 74.30 73.1 9 73.26 Ti02 0.31 0.28 0.27 0.30 0.29 Al203 14.31 14.51 13.97 14.66 14.49 Fe203 2.49 2.34 _ 2.14 2.19 2.27 MnO 0.07 0.07 0.07 0.06 0.06 M90 0.41 0.37 0.35 0.37 0.42 CaO 2.21 2.21 1.92 2.26 2.22 N320 2.48 2.31 2.22 2.67 2.66 K20 4.39 4.51 4.74 4.27 4.30 P205 0.02 0.02 . 0.02 0.02 . 0.02 Total 97.85 98.09 97.64 98.07 98.03 Rb 85 83 94 79 78 Sr 350 347 305 352 350 Zr 149 143 144 140 141 Laser ablation lCP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Ht Ta Th U 15.68 12.1 1 1858 28.46 51.63 5.53 18.62 3.40 0.98 0.53 2.35 0.49 1 .72 2.03 0.32 3.29 0.95 7.70 3.78 15.72 12.01 1869 28.35 53.47 5.45 17.94 3.26 1.01 0.52 2.32 0.49 1.67 1.98 0.31 3.19 1.01 7.67 3.85 15.95 12.51 1938 29.86 53.89 5.73 19.22 3.42 0.98 0.52 2.41 0.52 1.65 2.04 0.31 3.23 1.07 8.20 3.93 58 14.29 12.46 1832 27.63 51 .64 5.39 17.39 3.03 0.99 0.49 2.29 0.49 1.62 2.01 0.28 3.24 1.02 7.67 4.19 15.58 11.97 1847 28.56 51.56 5.67 18.76 3.40 1.02 0.53 2.49 0.49 1.68 1.96 0.32 3.22 0.95 7.60 3.71 Table 1 cont. (Salitral East) Sample 040706-7K 040706-7L 040706-7M 040706-7N 04070670 Location Longitude 85.15° 85.15° 85.15° 85.15° 85.15° Latitude 10.56° 10.56° 10.56° 10.56° 10.56° XRF analyses Si02 73.56 73.40 72.82 72.30 72.28 Ti02 0.30 0.29 0.31 0.35 0.34 Al203 14.24 14.43 14.96 15.26 15.10 Fe203 2.32 2.31 2.39 2.67 2.43 MnO 0.06 0.06 0.09 0.08 0.08 M90 0.44 0.39 0.35 0.46 0.49 CaO 2.16 2.26 2.26 2.27 2.40 N320 2.50 2.66 2.59 2.79 2.83 K20 4.41 4.19 4.21 3.81 4.02 P205 0.02 0.02 . 0.02 0.02 0.02 Total 98.03 98.23 97.63 97.98 97.76 Rb 82 78 76 67 72 Sr 335 355 356 344 363 Zr 139 141 151 177 156 Laser ablation lCP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Hf Ta Th U 16.58 12.19 1817 29.01 50.59 5.86 19.66 3.62 1.04 0.54 2.51 0.54 1.74 2.1 1 0.34 3.22 0.97 7.57 3.72 17.08 1 1 .43 1815 28.54 50.73 5.43 18.85 3.48 0.99 0.50 2.45 0.53 1.70 2.06 0.36 3.02 0.89 7.28 3.55 18.48 12.25 1801 31.43 66.18 6.44 23.21 4.49 1 .21 0.61 2.88 0.61 2.03 2.46 0.39 3.17 0.96 7.69 3.88 59 21.26 12.83 1722 34.88 57.96 7.19 25.49 4.92 1.24 0.65 3.27 0.72 2.17 2.79 0.48 3.92 1.00 8.32 3.96 19.28 11.94 1697 29.29 51.84 5.84 20.58 3.81 1.09 0.58 2.90 0.65 2.07 2.47 0.40 3.19 0.94 7.62 3.67 Table 1 cont. (Salitral East) Sample 040706-7P 040706-7Q 040707-28 040707-20 040707-20 Location Longitude 85.15° 85.1 5° 85.24° 85.24° 85.24° Latitude 10.56° 10.56° 10.57° 10.57° 10.57° XFiF analyses Si02 72.46 71.61 74.01 73.12 73.49 Ti02 0.33 0.36 0.26 0.31 0.28 AI203 14.94 15.76 15.23 14.52 14.62 Fe203 2.50 2.81 2.01 2.44 . . 2.16 MnO 0.08 0.08 0.09 0.13 0.08 M90 0.54 0.47 0.30 0.42 0.40 C30 2.35 2.32 1.57 2.24 2.10 Na20 2.59 2.73 2.59 2.45 2.24 K20 4.20 3.84 3.93 4.35 4.61 P205 0.02 0.02 0.01 0.02 0.02 Total 97.95 97.84 97.08 97.80 97.06 Rb 74 64 89 84 87 Sr 348 355 230 343 327 Zr 159 168 128 149 143 Laser ablation ICP-MS analyses Y Nb Ba La Ce Pr Nd Srn Eu Tb Dy Ho Er Yb Lu Ht Ta Th U 23.91 12.39 1743 36.23 56.86 7.34 27.21 5.22 1.36 0.73 3.72 0.80 2.61 2.96 0.49 3.45 1.01 7.93 3.93 24.71 13.35 1738 43.63 60.95 8.77 30.81 5.57 1.38 0.78 3.66 0.75 2.38 2.95 0.46 3.73 0.96 8.24 4.05 1 1 .07 7.47 1199 22.27 35.40 4.72 16.14 3.20 0.90 0.42 2.07 0.42 1.35 1 .92 0.30 2.85 0.61 5.1 1 2.30 60 16.46 1 1 .52 1952 30.18 62.46 5.90 20.20 3.57 1.03 0.51 2.64 0.55 1.85 2.06 0.31 3.19 0.89 7.89 3.81 15.30 11.24 1914 28.88 53.26 5.81 19.69 4.04 1.14 0.51 2.62 0.54 1.69 2.28 0.38 4.22 0.89 8.21 3.70 Table 1 cont. (Salitral East) Samale 040707-2E 040707-2F 040707-2G 040707-2H 040707-2i Location Longitude 85.24° 85.24° 85.24° 85.24° 85.24° Latitude 10.57° 10.57° 10.57° 10.57° 10.57° XRF analyses Si02 72.89 72.68 73.12 73.15 73.26 Ti02 0.34 0.33 0.30 0.31 0.31 Al203 14.47 14.65 14.67 14.61 14.43 Fe203 2.67 2.62 2.36 2.27 2.38 MnO 0.07 0.07 0.09 0.06 0.08 M90 0.44 0.44 0.32 0.34 0.44 CaO 2.34 2.28 2.27 2.29 2.29 N320 2.59 2.50 2.27 2.52 2.75 K20 4.18 4.40 4.59 4.43 4.03 P205 0.02 0.02 0.02 0.02 0.02 Total 97.81 97.25 97.43 97.10 97.76 Rb 74 82 80 80 75 Sr 352 338 352 354 345 Zr 148 147 140 144 149 Laser ablation lCP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy H0 Er Yb Lu Ht Ta Th U 16.12 11.19 1782 29.65 48.74 6.10 21.05 4.22 1.16 0.54 2.77 0.57 1.79 2.34 0.38 4.17 0.84 7.76 3.45 11.27 1770 30.18 49.23 6.24 21.53 4.13 1.20 0.57 4.09 0.87 7.86 3.67 14.85 1 1 .27 1878 29.40 53.97 6.01 20.45 3.98 1.16 0.53 2.55 0.52 1.69 2.27 0.37 3.86 0.86 7.79 3.74 61 15.33 11.83 1847 30.81 49.77 6.33 21.52 4.14 1.16 0.53 2.68 0.55 1.76 2.35 0.37 4.07 0.89 7.84 3.92 16.37 11.02 1792 30.00 54.70 6.28 21.38 4.19 1.18 0.54 2.74 0.57 1.87 2.37 0.37 4.18 0.83 7.87 3.44 Table 1 cont. (Salitral East) 62 Sample 040707-2J 040706-9A 040706-9B 040706-9C 040706-8A Location Longitude 85.24° 85.16° 85.16° 85.16° 85.16° Latitude 10.57° 10.60° 10.60° 10.60° 10.60° XRF analyses Si02 73.56 72.36 70.91 71.13 72.60 Ti02 0.30 0.31 0.34 0.34 0.35 Al203 14.24 15.17 16.72 16.37 14.97 Fe203 2.38 2.50 2.55 2.51 2.68 - . MnO 0.06 0.06 0.07 0.07 0.08 M90 0.37 0.44 0.42 0.53 0.62 CaO 2.14 2.33 2.54 2.54 2.18 Na20 2.47 2.59 2.70 2.86 2.36 K20 4.46 4.21 3.72 3.64 4.14 P205 0.02 0.02 0.02 0.02 0.02 Total 97.23 96.89 96.95 97.36 98.25 Rb 79 83 69 67 79 Sr 322 355 398 390 319 Zr 148 153 171 163 163 Laser ablation ICP-MS analyses Y 16.19 15.66 16.95 19.62 18.18 Nb 11.26 12.11 13.09 13.73 12.82 Ba 1775 1786 1854 1774 1743 La 29.91 29.43 33.19 31.94 28.04 Ce 47.60 49.20 54.96 51 .17 50.66 Pr 5.98 6.21 6.77 7.29 5.81 Nd 20.21 20.95 22.33 23.40 19.87 Sm 3.97 3.91 3.94 3.90 3.80 Eu 1.09 1.14 1.19 1.21 1.05 Tb 0.50 0.57 0.60 0.62 0.61 Dy 2.70 2.73 2.87 3.08 2.97 Ho 0.56 0.53 0.56 0.62 0.61 Er 1.80 1.74 1.83 2.07 2.04 Yb 2.40 2.02 2.39 2.57 2.46 Lu 0.39 0.32 0.36 0.39 0.41 Hf 4.16 3.37 3.66 3.59 3.80 Ta 0.88 0.96 1.03 1.01 0.99 Th 8.14 7.70 8.56 8.58 8.23 u 3.56 3.76 4.22 4.17 4.05 Table 1 cont. (Salitral East) Sample 040706-8B 040706-8C 040706-8D 040706-8E 0407075 Location Longitude 85.16° 85.16° 85.16° 85.16° 85.23° Latitude 10.60° 10.60° 10.60° 10.60° 10.63° XRF analyses Si02 71.58 71.79 71.73 72.22 72.13 Ti02 0.32 0.33 0.35 0.32 0.35 Al203 16.20 15.94 15.66 15.31 15.37 Fe203 2.54 2.53 2.69 2.48 3.04 MnO 0.09 0.07 0.10 0.12 0.10 M90 0.57 0.58 ' 0.56 0.46 0.50 CaO 2.38 2.24 2.41 2.33 2.22 Na20 2.53 2.46 2.67 2.50 2.32 K20 3.77 4.03 3.80 4.24 3.95 P205 0.02 0.02 0.02 0.02 0.02 Total 97.33 96.43 97.04 96.68 96.90 Rb 67 81 76 88 79 Sr 351 337 370 362 328 Zr 165 171 169 163 164 Laser ablation ICP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Ht Ta Th U 16.46 12.57 1726 27.33 56.56 5.60 19.03 3.58 1.23 0.51 2.55 0.62 1.83 2.06 0.34 3.68 1.02 8.1 1 19.40 1711 30.57 51.35 5.97 20.46 4.10 1.21 0.59 3.00 0.85 2.60 2.72 0.44 15.73 12.62 1850 27.60 53.54 5.66 18.76 3.63 1.1 1 0.56 2.63 0.52 1.74 1.96 0.30 3.63 0.96 7.70 4.03 63 14.1 1 12.59 1931 27.60 54.73 5.40 18.13 3.25 1.05 0.45 2.21 0.57 1.67 1.80 0.29 3.46 0.95 7.49 18.47 13.04 1790 31.02 62.36 6.70 23.03 4.09 1.15 0.55 2.83 0.71 2.02 2.26 0.38 3.59 1.01 7.57 Table 1 cont. (Virginia) Same 010627-3i 010629-1 a 020709-3c 020709-3d 020709-3g_ Location Longitude 85.42° 85.35° 85.38° 85.38° 85.38° Latitude 10.72° 10.54° 10.75° 10.75° 10.75° XRF analyses Si02 73.12 78.73 73.81 73.85 72.43 Ti02 0.23 0.21 0.36 0.40 0.44 Al203 16.41 11.89 14.63 14.75 14.95 Fe203 1.74 1.50 2.39 2.71 3.30 MnO 0.08 80.04 0.08 0.08 0.08 M90 0.26 0.39 0.46 0.51 0.61 CaO 1.61 1.67 2.02 1.98 2.25 NaZO 2.65 2.36 1.83 ‘ 1.69 2.35 K20 3.86 3.16 4.35 3.97 3.52 P205 0.04 0.05 0.05 . 0.05 0.07 Total 96.00 98.00 95.32 95.03 96.12 Rb 85 78 92 86 76 Sr 238 252 290 278 307 Zr 1 40 1 04 221 224 222 Laser ablation ICP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Ht Ta Th U 19.25 10.31 3687 28.3 51.76 5.12 16.23 2.91 0.99 0.47 2.4 0.53 1.69 3.26 0.42 3.4 1.34 9.14 6.14 12.45 8.56 2328 27.21 37.82 4.76 14.92 2.65 0.79 0.37 1.82 0.38 1.15 1.94 0.23 2.54 1 .12 6.25 5.49 15.88 9.19 1767 29.04 53.12 5.97 19.8 3.58 1.01 0.51 2.65 0.49 1.59 2.15 0.31 4.89 1.14 8.42 5.41 17.21 9.53 1797 29.63 53.81 6.07 20.45 3.69 1 .02 0.55 2.76 0.54 1 .67 2.19 0.33 5.15 1 .05 8.58 5.37 23.86 8.2 1671 30.16 52.85 7.05 27.54 4.89 1.37 0.79 3.96 0.77 2.33 2.87 0.45 5.25 1.1 1 8.41 5.06 Table 1 cont. (Virginia) Sample 020709-3h 020709-4a 020709-4b 020709-4c 02071 2-1 b 020712-1 0 Location Longitude 85.38° 85.42° 85.42° 85.42° 85.46° 85.46° Latitude 10.75° 10.72° 10.72° 10.72° 10.70° 10.70° XRF analyses Si02 72.93 68.90 71.01 70.79 69.58 71.20 Ti02 0.40 0.47 0.47 0.42 0.43 0.48 Al203 14.89 18.22 15.62 16.01 17.21 15.14 Fe203 2.75 3.60 3.47 3.18 3.36 3.82 MnO 0.15 0.12 0.12 . 0.07 0.08 . . 0.07 M90 0.54 0.42 0.37 0.38 0.32 0.58 CaO 2.29 2.21 2.32 2.50 2.70 2.16 NaZO 2.44 2.28 2.18 2.35 2.26 2.50 K20 3.57 3.73 4.38 4.24 4.01 4.00 P205 0.05 0.05 0.05 0.05 0.05 0.05 Total 96.09 95.54 96.70 97.03 96.80 96.80 Rb 77 78 93 87 83 84 Sr 318 325 346 369 406 320 Zr 219 208 21 1 203 209 224 Laser ablation lCP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Ht Ta Th U 18.2 8.8 1773 29.86 54.2 6.39 22.73 4.1 1.2 0.58 2.96 0.61 1.78 2.39 0.36 5.02 1.03 8.1 1 5.01 21.95 10.49 1993 35.17 73.93 8.87 33.19 6.4 1.46 0.83 3.99 0.8 2.47 3.02 0.41 5.12 1.4 9.77 8.05 21.1 12.05 1964 36.46 70.49 8.4 29.89 5.58 1.34 0.78 3.68 0.71 2.22 2.73 0.41 5.07 1.27 9.26 6.63 65 20.8 10.24 1860 36.27 61.5 8.04 29.52 5.52 1.36 0.74 3.56 0.69 2.15 2.63 0.41 4.95 1.12 9.18 5.41 19.43 8.52 1862 34.38 61.78 7.97 29.15 5.62 1.47 0.70 3.63 0.80 2.23 2.58 0.40 4.89 1.22 9.26 6.06 19.27 11.37 1776 32.64 61.55 7.01 24.80 4.68 1.13 0.61 3.28 0.61 1.97 2.62 0.39 5.29 1.25 9.98 5.56 Table 1 cont. (Virginia) Sample 020712-1d Location Longitude 85.46° Latitude 10.70° XRF analyses Si02 70.57 TiOz 0.38 Al203 17.10 Fe203 2.88 MnO 0.07 M90 0.29 CaO 1 .99 Na20 2.31 K20 4.36 P205 0.05 Total 95.60 Rb 91 Sr 305 Zr 198 Laser ablation ICP-MS analyses Y 17.79 Nb 10.33 Ba 1936 La 31.88 Ce 59.02 Pr 6.64 Nd 23.15 Sm 4.22 Eu 1.12 Tb 0.60 Dy 3.02 Ho 0.58 Er 1.87 Yb 2.37 Lu 0.37 Hf 5.45 Ta 1.49 Th 10.92 U 5.39 Table 1 cont. (Liberia) Sample 990718-1-1 990718-1-2 990718-1-3 990718-1-4 990718-1-5 Location Longitude 85.26° 85.26° 85.26° 85.26° 85.26° Latitude 10.56° 10.56° 10.56° 10.56° 10.56° XFiF analyses Si02 72.23 74.77 72.96 73.78 74.12 Ti02 0.29 0.21 ' 0.25 0.26 0.22 Al203 17.13 14.04 16.03 15.53 14.80 Fe203 2.00 1.56 1.61 1.78 1.59 MnO 0.04 0.07 0.06 0.06 0.07 M90 0.49 0.35 0.41 0.44 0.37 CaO 1.57 1.64 1.69 1.53 1.72 NaZO 2.32 2.40 2.51 2.18 2.45 K20 3.92 4.93 4.45 4.42 4.64 P205 0.02 0.02 0.02 0.02 0.02 Total 98.00 98.00 97.00 98.00 98.00 Rb 94 104 1 10 109 1 15 Sr 241 249 257 239 263 Zr 150 133 135 146 127 Laser ablation ICP-MS analyses 13.87 8.98 1591 24.67 50.25 5.49 19.78 3.73 1.06 0.46 2.47 0.45 1.37 2.1 1 0.31 4.23 2.07 9.46 3.51 10.62 7.45 1660 20.91 36.87 4.1 12.85 2.46 1.09 0.36 1.84 0.35 0.91 1.87 0.24 3.14 1.68 7.53 3.22 14.17 6.9 1651 26.25 46.56 4.93 16.34 2.67 0.63 0.33 1.95 0.42 1.32 1.58 0.26 3.45 1 .12 9.47 5.8 67 10.87 8.17 1779 22.23 43.74 4.23 14.51 2.44 0.87 0.37 1.81 0.34 1.22 1.87 0.2 3.99 2.1 8.07 3.83 19.9 6.6 1579 34.1 Table 1 cont. (Liberia) Sample 990718-1-6 990718-1-7 990718-1-8 990718-1-9 990718-1-10 Locaflon Longitude 85.26° 85.26° 85.26° 85.26° 85.26° Latitude 10.56° 10.56° 10.56° 10.56° 10.56° XRF analyses Si02 74.29 73.61 76.10 73.51 74.19 Ti02 0.24 0.24 0.22 0.27 0.24 AI203 14.26 15.12 13.44 14.99 14.49 Fe203 1.70 1.86 . _ 1.38 1.91 1.64 MnO 0.06 0.05 0.05 0.07 0.06 M90 0.48 0.35 0.34 0.52 0.41 CaO 1.83 1.76 1.65 1.70 1.73 Na20 2.76 2.62 2.57 2.43 2.82 K20 4.36 4.38 4.22 4.58 4.40 P205 0.02 0.02 0.02 0.02 0.02 Total 99.00 98.00 100.00 98.00 97.00 Rb 1 15 92 101 121 89 Sr 281 274 262 256 264 Zr 138 142 113 142 144 Laser ablation lCP-MS analyses Y 9.54 12.13 9.33 11 9.54 Nb 7.1 7.64 7.61 7.66 7.63 Ba 1721 1749 1545 1820 1793 ka 21.53 23.65 19.1 1 23.21 22.08 Ce 38.16 42.88 33.33 40.28 39.83 Pr 4.25 4.58 3.71 4.39 4.16 Nd 13.59 16.48 11.01 14.45 13.36 Sm 2.17 2.73 2.28 2.15 2.08 Eu 0.95 1.1 1.1 0.92 1 To 0.36 0.38 0.31 0.39 0.32 by 1.75 1.98 1.31 1.89 1.76 Ho 0.29 0.38 0.3 0.34 0.29 Si 0.97 1.11 0.92 1.09 0.9 V6 1.86 2.04 1.59 2.12 1.73 Lu 0.18 0.3 0.21 0.23 0.21 H1 3.6 3.74 2.72 4.01 3.49 To 1.54 1.74 1.5 1.98 1.84 Tn 7.19 7.59 6.49 8.35 7.79 Ll 3.45 3.64 2.92 3.37 3.86 68 llllU Table 1 cont. (Liberia) Sample 990718-1-11 990718-1-12 990718-1-13 020712-1b 02071210 Location Longitude 85.26° 85.26° 85.26° 85.46° 85.46° Latitude 10.56° 10.56° 10.56° 10.70° 10.70° XRF analyses 3102 72.75 73.98 73.69 69.58 71.20 Tio2 0.29 0.22 0.28 0.43 0.48 Al203 16.22 15.02 14.63 17.21 15.14 Fe203 2.05 1.61 2.05 , 3.36 3.82 MnO 0.05 0.05 0.06 0.08 0.07 M90 0.47 0.35 0.65 0.32 0.58 C30 1.66 1.66 1.82 2.70 2.16 N320 2.62 2.39 2.76 2.26 2.50 K20 3.87 4.69 4.05 4.01 4.00 P205 0.02 0.02 0.02 0.05 0.05 Total 97.00 98.00 98.00 96.80 96.80 Rb 86 108 120 83 84 Sr 253 251 257 406 320 Zr 160 143 167 209 224 Laser ablation ICP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Ht Ta Th U 13.06 8.22 1701 26.14 48.83 5.56 19.22 3.61 1.13 0.45 2.45 0.41 1 .34 2.01 0.32 3.82 1 .99 8.39 3.6 12.07 7.55 1744 25.59 46.43 5.45 18.77 3.27 1.08 0.4 2.12 0.37 1.25 1.9 0.27 3.55 1.95 8.21 3.82 14.45 7.4 1608 25.62 44.62 5.53 19.84 3.67 1.07 0.5 2.45 0.46 1.41 2.02 0.27 4.16 1.66 7.91 3.3 69 19.43 8.52 1862 34.38 61.78 7.97 29.15 5.62 1 .47 0.7 3.63 0.8 2.23 2.58 0.4 4.89 1.22 9.26 6.06 19.27 1 1.37 1776 32.64 61 .55 7.01 24.8 4.68 1.13 0.61 3.28 0.61 1.97 2.62 0.39 5.29 1 .25 9.98 5.56 Table 1 cont. (Liberia) Sample 020712-1d 020712-1 e 020712-1t 020712'1L 02071219 #1 Location Longitude 85.46° 85.46° 85.46° 85.46° 85.46° Latitude 10.70° 10.70° 10.70° 10.70° 10.70° XRF analyses Si02 70.57 73.74 74.31 73.43 74.38 Ti02 0.38 0.20 0.20 0.22 0.21 Al203 17.10 15.48 15.30 16.34 14.83 Fe203 2.88 1.57 1.56 1.52 1.57 ‘ MnO 0.07 0.06 0.07 0.06 0.06 M90 0.29 0.24 0.18 0.26 0.23 CaO 1.99 1.49 1.35 1.24 1.48 NaZO 2.31 2.35 2.30 2.13 2.35 K20 4.36 4.82 4.71 4.76 4.86 P205 0.05 0.05 0.04 0.05 0.04 Total 95.60 97.40 97.10 96.30 96.60 Rb 91 109 104 108 1 10 Sr 305 214 197 198 225 Zr 198 116 144 135 136 Laser ablation lCP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Hf Ta Th U 17.79 10.33 1936 31.88 59.02 6.64 23.15 4.22 1 .12 0.6 3.02 0.58 1.87 2.37 0.37 5.45 1.49 10.92 5.39 11.82 8.47 1985 26.84 52.34 4.8 15.65 2.6 0.72 0.36 1.91 0.4 1.3 1.9 0.27 3.71 1.8 11.96 7.13 70 1 1.24 7.11 1936 26.6 49.57 4.67 15.16 2.19 0.74 0.36 1.82 0.36 1.18 1.84 0.27 3.55 1.59 10.69 6.89 Table 1 cont. (Liberia) Sample 020712-19 #2 02071.2;1g #4 Location Longitude 85.46° 85.46° Latitude 10.70° 10.70° XRF analyses Si02 73.81 75.09 Ti02 0.1 9 0.1 5 A1203 15.31 14.61 F9203 1 .51 1 .24 MnO 0.07 0.06 M90 0.22 0.08 CaO 1 .76 1 .47 NaZO 3.08 2.57 K20 4.01 4.68 P205 0.04 0.04 Total 97.60 98.1 0 Rb 94 98 Sr 262 230 Zr 1 27 1 1 8 Laser ablation lCP-MS analyses Y 13.09 1 1 .42 Nb 4.85 4.88 Ba 2326 1918 La 28.89 26.81 Ce 50.71 46.95 Pr 4.67 4.48 Nd 15.56 15.04 Sm 2.54 2.35 Eu 0.8 0.66 Tb 0.38 0.36 Dy 2.05 1.84 Ho 0.47 0.4 Er 1.6 1 .31 Yb 1.89 1.8 Lu 0.32 0.27 Ht 3.73 3.34 Ta 1.42 1.39 Th 10.72 1 1 .44 u 5.72 6.6 71 Table 1 cont. (Buena Vista) Sample 990718-2b-1 99071 8-2b-2 99071 8-2c 990718-2d-1 99071 8-2d-2 Locafion Longitude 85.24° 85.24° 85.24° 85.24° 85.24° Latitude 10.62° 10.62° 10.62° 10.62° 10.62° XRF analyses Si02 69.79 70.03 67.92 72.33 68.49 Ti02 0.52 0.50 0.53 0.32 0.53 A|203 15.46 15.52 16.72 15.18 16.53 Fe203 3.92 3.55 4.07 2.52 4.19 MnO 0.11 0.15 0.11 0.08 0.07 M90 0.70 0.65 1.04 0.61 0.52 CaO 3.01 2.78 3.35 2.28 3.14 NaZO 2.97 2.84 2.90 2.77 2.61 K20 3.46 3.93 3.32 3.89 3.86 P205 0.05 0.05 _ 0.03 0.02 0.05 Total 98.00 97.00 98.00 98.00 98.00 Rb 60 71 58 77 74 Sr 41 6 377 404 370 427 Zr 206 215 212 158 204 Laser ablation lCP-MS analyses Y 17.63 20.21 20.99 17.18 18.35 Nb 9.01 8.63 8.87 10.46 8.68 Ba 1699 1690 1455 1721 1548 La 24.94 25.86 25 31.89 24.43 Ce 61.16 56.63 55.32 56.23 47.71 Pr 5.91 6.47 6.56 6.61 5.42 Nd 22.05 22.51 26.21 22.17 20.27 Sm 4.35 4.75 5.61 3.89 3.77 Eu 1.22 1.61 1.69 1.25 1.28 Tb 0.56 0.68 0.71 0.49 0.58 Dy 2.82 3.45 3.41 2.71 2.67 Ho 0.45 0.64 0.72 0.52 0.44 Er 1.95 1.86 1.98 1.56 2.16 Yb 2.29 2.68 2.74 2.28 2.23 Lu 0.34 0.38 0.39 0.36 0.34 Ht 3.79 4.81 3.61 3.95 3.73 Ta 0.96 1.2 0.9 1.42 0.92 Th 4.16 5.86 4.05 8.27 4.31 U 2.69 2.74 2.61 2.73 2.16 72 Table 1 cont. (Buena Vista) Sample 990718-2d-3 990718-2d-4 990718-2d-5 990718-33 990718-3-1 Location Longitude 85.24° 85.24° 85.24° 85.23° 85.23° Latitude 10.62° 10.62° 10.62° 10.62° 10.62° XFiF analyses Si02 72.90 69.97 68.79 72.48 73.05 Ti02 0.32 0.49 0.50 0.33 0.30 Al203 14.71 15.87 16.95 14.62 14.42 Fe203 2.41 3.82 3.50 2.63 2.50 MnO 0.07 0.08 0.10 0.07 0.07 M90 0.65 0.34 0.71 0.67 0.54 CaO 2.28 2.74 3.11 2.28 2.21 NaZO 2.81 2.41 2.74 2.87 2.55 K20 3.81 4.22 3.59 4.03 4.32 P205 0.03 0.04 . 0.03 0.02 0.02 Total 98.00 97.00 98.00 98.00 99.00 Rb 85 80 58 80 84 Sr 368 379 385 368 357 Zr 160 212 219 166 156 Laser ablation ICP-MS analyses Y 11.6 23.14 18.58 13.26 14.67 Nb 10.15 8.78 8.98 10.15 10.2 Ba 1735 1624 1 310 1733 1807 La 28.23 28.73 25.8 30.04 35.68 Ce 47.68 54.32 53.34 51.33 61.24 Pr 5.13 6.59 5.83 5.86 7.09 Nd 17.3 26.12 21.69 20.1 24.25 Sm 2.85 5.02 4.34 3.32 4.08 Eu 0.96 1.34 1.16 1.05 1.14 Tb 0.36 0.66 0.58 0.42 0.46 Dy 1.77 3.41 3.36 2.15 2.36 Ho 0.21 0.62 0.67 0.34 0.36 Er 1.08 2.19 2.07 1.45 1.51 Yb 1.58 2.71 2.4 2.01 2.03 Lu 0.22 0.44 0.38 0.31 0.33 Ht 3.05 4.5 5.73 3.42 3.31 Ta 1.32 1 0.86 1.26 1.38 Th 6.24 4.94 5.93 6.51 6.39 U 2.52 2.33 2.35 2.62 2.84 73 Table 1 cont. (Buena Vista) Laser ablation lCP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Ht Ta Th U 14.73 11.14 1743 37.26 60.38 7.76 28.58 4.87 1 .26 0.55 2.82 0.58 1 .74 2.26 0.35 3.73 1 .23 7.81 2.79 15.22 9.59 1709 32.44 52.29 6.17 21.92 3.7 1 .09 0.46 2.3 0.39 1 .45 1 .87 0.3 3.79 1 .21 6.74 2.44 14.16 9.66 1798 32.33 48.1 1 6.01 21.23 3.58 1.07 0.43 2.21 0.32 1.38 1.89 0.32 3.59 1.24 6.75 2.46 74 13.32 10.7 1679 34.62 52.63 6.53 23.04 3.52 1.04 0.47 2.46 0.49 1.57 2.15 0.31 3.66 1.27 8.03 2.63 Sample 99071 8-3-2 99071 8-3-3 99071 8-3-4 99071 8-3-5 99071 8-3—6 Location Longitude 85.23° 85.23° 85.23° 85.23° 85.23° Latitude 10.62° 10.62° 10.62° 10.62° 10.62° XRF analyses Si02 72.04 72.71 72.83 73.34 72.18 Ti02 0.32 0.33 0.31 0.31 0.31 Al203 14.88 14.37 14.63 14.12 15.00 Fe203 2.52 2.61 2.36 . 2.44 2.49 MnO 0.07 0.07 0.06 0.07 0.07 M90 0.61 0.77 0.60 0.65 0.67 C30 2.33 2.23 2.28 2.17 2.42 N320 3.05 2.68 2.53 2.58 2.74 K20 4.14 4.23 4.38 4.31 4.09 P205 0.02 0.02 0.02 0.02 0.02 Total 1 00.00 98.00 98.00 99.00 99.00 - Rb 86 90 82 81 78 Sr 395 350 373 347 401 Zr 155 166 160 154 164 14.88 9.72 1765 33 55.57 6.46 22.71 3.87 1.13 0.47 2.31 0.38 1.56 1.95 0.32 3.24 1.29 6.39 2.62 Table 1 cont. (Buena Vista) Sample 99071 8-3—7 99071 8-3-8 990718-4-1 990718-4a 99071 8-4-2 Location Longitude 85.23° 85.23° 85.23° 85.23° ‘ 85.23° Latitude 10.62° 10.62° 10.62° 10.62° 10.62° XRF analyses Si02 72.39 72.65 73.30 72.87 72.57 Ti02 0.33 0.32 0.31 0.32 0.34 Al203 14.70 14.69 14.39 14.55 14.42 Fe203 2.68 2.51 2.41 2.52 2.76 _ MnO. _ 0.09 0.09 0.08 0.08 0.08 M90 0.69 0.60 0.53 0.60 0.68 CaO 2.28 2.23 2.06 2.13 2.27 NaZO 2.85 2.75 2.56 2.61 2.82 K20 3.96 4.14 4.33 4.31 4.03 P205 0.02 0.02 0.02 0.02 0.02 Total 98.00 98.00 98.00 97.00 97.00 Rb 75 78 88 81 79 Sr 369 337 348 355 Zr 166 159 154 161 166 Laser ablation lCP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Hf Ta Th U 19.3 1 1 .55 1745 38.54 66.35 8.53 32.25 5.37 1 .38 0.62 3.36 0.71 2.01 2.63 0.42 3.73 1 .3 7.69 2.9 17.08 10.23 1771 34.88 61 .95 7.39 23.98 3.91 1 .26 0.54 2.72 0.52 1 .62 2.21 0.36 3.71 1 .57 8.75 2.95 75 14.16 11.36 1739 35.29 55.3 6.58 22.89 3.76 1.07 0.47 2.43 0.49 1 .67 2.14 0.36 3.77 1.33 7.86 2.84 11.92 11.05 1664 35.12 57.18 6.41 22.2 3.78 1.08 0.47 2.36 0.48 1.41 2.06 0.3 3.87 1.2 7.5 2.76 Table 1 cont. (Buena Vista) Sample 99071 8-4-3 99071 8-4-4 990718-4-5 Location Longitude 85.23° 85.23° 85.23° Latitude 10.62° 10.62° 10.62° XRF analyses Sl02 72.42 72.15 72.55 Ti02 0.34 0.32 0.33 Al203 14.72 14.86 14.58 Fe203 2.61 2.54 2.58 MnO 0.07 0.07 0.08 M90 0.67 0.76 0.70 CaO 2.31 2.50 2.37 N320 2.64 2.71 2.66 K20 4.21 4.07 4.12 P205 0.02 0.02 0.02 Total 98.00 98.00 98.00 Rb 81 77 79 Sr 372 397 374 Zr 153 1 58 163 Laser ablation lCP-MS analyses Y Nb Ba La Ce Pr Nd Sm Eu Tb Dy Ho Er Yb Lu Ht Ta Th U 12.31 1 1 .09 1747 33.43 53.41 6.22 21 .34 3.72 1.1 0.45 2.42 0.47 1.44 1.93 0.31 3.57 1.33 7.29 2.81 1 1 .62 10.42 1658 32.84 50.46 6.13 21 .17 3.69 1.1 1 0.46 2.23 0.47 1.37 1.76 0.27 3.77 1.16 7.23 2.52 13.03 10.35 1655 35.35 50.24 6.39 22.38 3.89 1 .08 0.45 2.55 0.51 1.44 2.03 0.3 3.9 1.19 7.46 2.49 76 New .8996 5285820 88: .35 momma 305.6 «529 62.9.? .0 9:9“. as on 8 8 8 8 9 8 8 q—uuqd—qdud—ud-u—u-uu—qu q—uuu- qq- —q<-u r r 3595 + saw .258 o .23.. 59.6 a. 32.9.65 9.25 G 355 0 292.3 Scam .1 52-365 265m 4 6:3: u 26.6". 35m 0 I. l l l 1 I. 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There are slight decreases in middle rare earth elements (MREE), heavy rare earth elements (HREE), and Sr with increasing SiOz content. However, the Green Layer unit is a notable outlier in HREE, displaying lower values than the other samples from the same Si02 range. Light rare earth elements (LREE) content remains relatively constant between the two SiOz groups. . Spider diagrams for each of the seven geochemical units are depicted in Figures 9 and 10. Figure 9 (normalized to primitive mantle) displays enrichment in large ion lithophiles (LIL) and depletion in the HFSE and Phosphorus. The first two patterns are similar to magmas generated in subduction zone environments. Figure 10 (normalized to chondrite) shows all of the units are enriched in LREE and some units are depleted in MREE relative to the HREE. The Green Layer and some selected samples of the Santa Fe-high/low do not display the HREE depletion. The Santa Fe unit range of REE trends encompass all of those displayed by the other units. The units defined in this study have slight positive and negative anomalies (Eu/Eu* range 1.57-0.55) and all have slight negative anomalies (Eu/Eu* 0.5-0.8). The cumulative frequency distribution of incompatible trace element ratios aided in identifying compositional distinctions among the set of ash-flow sheets (Figure 11). This type of statistical data analysis can separate the data set based on the frequency 79 «9w m=20> Esozm :ozatg EoEQo mom: i Emigfiomm 3:3 8:55 .m 059... £595 + «mom .553 o .96.. :090 0 Bo_-8m_> 233 Q @2335 mcosm 4 age 0 32.6". Seam .1 «:3: D 32.0". 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Equally incompatible elements would not be affected by processes of differentiation such as fractional crystallization or low degrees of partial melting. Therefore, these types of element ratios are used to discriminate among ash-flow sheets from independent sources. Figure lla,b displays two incompatible trace element ratios that could be affected by processes related to melting processes in subduction zones. Nb/T a ratios were used to distinguish among the seven compositionally distinct ash-flow sheets (Figure 11a). These ash-flow sheets display a wide range of Nb/T a values from 4 to 29. The seven units, including high and low silica subgroups of the Santa Fe and Buena Vista, with corresponding Nb/T a averages (:1: 1 standard deviation) are as follows: Green Layer (25.15 :25), Santa Fe-low (15.22 11.14), Santa Fe-high (15.20 11.37), Salitral East (12.81 :t 0.50), Pijije (10.57 01.09), Liberia (4.34 11.39), Virginia (8.13 10.92), Buena Vista-low (9.18:1.12), Buena Vista-high (8.15:0.75). The high and low silica groups of Santa Fe have very similar Nb/T a ratios with little deviation from the mean. In comparison the Buena Vista groups are within their respective standard deviations from one another, but the Buena Vista-high appears to be more similar to the Virginia unit. In comparison to other ignimbrite deposits from the Central American arc, the Nb/Ta ratios in these samples cover a wider range than all the other samples (Figure 12). In contrast, 84 the Zr/Hf ratios show significant overlaps and breaks in unit cumulative frequency (Figure 11b). 85 0.00.00 2.0020000 0... 80.. 000:. :0:. .080 0.0 0... 0:20 0:00. 020800 02:0 :0.: 08000.00. 00.0 >80 02¢ 0.000 .8800 0. .003: 0.080.000-0285. 80.. 00.30008 0. 0.0 0:. 0:20 00:00.0 0.0 0.... 0:20 020800 .00.; mm A N0.9 02:0 :0.: 0.... .0 :0 0000008005 0.00.00 2.00.:0000 0:. .0 028:0 02:080.: 80.. 0 0.32 .0 00:0. 0:... .0. 0.00.". .80.. 0.0 0:0.0 00:0.05 com o .23.. 000.0 .0. 20...-.. 2:00 a. .50—10”. Scam a. .80 .0800 o .. 2.... 0 0583.0 0505... 22.0.05 0:05 4 :0..-0.0.> 0:80 4 0.32 0.00.022 80020.0. .m. 0.080.000 — p — _ p — — n on 86 Variation diagrams that plot incompatible trace element ratios with one of the elements on a log scale are used to compare the compatibility of the two elements and determine systematic relationships among units. The slope of the trends displayed in Figures 11c,d indicate a systematic control of Ta and Hf over there respective ratios. This variation could be due to the same phase controlling the trace element (e. g. Ta) partitioning (e. g. amphibole) among the units. 2. Petrographic analyses Petrographic analyses were performed on thirty-six thin sections representing pumice samples from each of the seven units (Appendix B). Pumice are hypocrystalline with degrees of crystallinity typically between 7% and 20%, although several thin sections have crystallinity values as high as 50%. Most samples display a glassy groundmass, but some samples have plagioclase microlites. Some of the pumice samples with the plagioclase microlites display an intermediate to strong trachytic texture (i.e. Pijije, Santa Fe-low/high). Primary mineralogy consists of plagioclase, (low/high-Mg) amphiboles, biotite, and quartz with trace amounts of Fe-Ti oxides (magnetite and ilmenite), zircon, and apatite (Figure 13). Table 2 lists the representative averages of mineral abundances for each of the units given as estimated modal percentages. An estimated average of the mineral sizes is also provided. Twinning is common among both plagioclase and amphibole, and many of the plagioclase grains display oscillatory zoning. Melt inclusions are abundant in plagioclase and amphibole - many are completely devitrified. Several disequilibrium textures (i.e. resorbtion, embayment, corroded plagioclase cores) are 87 ..0_0 2.030.000.0820 0 .0 0000 0:. .0 020.0 000.00.00_0 0:0 0.02:080 .0203. 3 0.00.0. 800:...00000 0.:. ..:.:x0 00.0800 00.800 000:. 2 0:00. 5.000 0:. .0 nx00 00:. 0.08 A0. 2 5.000 000.000. 0:. 0.02 0.0.028 :08800 .008 0:. 0.0 5.000 0:0 0.00.: 2002080 000.0200... 00.0 0.2.0:. 2 0.80 80.020 0:. .0 0.0.028 0>_.0.:000.00. 022.20 080800.. 00.800 .0 30x. 300.00.280.08“. 0.00. 0.00.... 200.5 88 Table 2 Pemraphlc summary Unit! Sample Plagioclase Amphibole Biotite Quartz Opaques Modal % Modal % Modal % Modal % Modal % Buena Vista-low 990718-20 15 2 3 Size (mm) 0.05-2.875 0.125-1.5 0.025-0.75 Buena Vista-Ligh 990718-2D-1 15 2 2 990718-20-3 10 1 2 990718-3a 15 1 «1 1 990718—3-1 10 1 <1 1 1 990718-3-4 7 2 <1 <1 990718-3-5 7 <1 <1 <1 1 990718—3-6r 10 2 <1 1 1 990718—4-5 15 2 4 2 Size (mm) 0.05-2.875 0.075—225 0.125-.625 0.05-2.5 0.025-1.0 Virginia 020709-3a 4 <1 1 020709-40 3 <1 1 Size (mm) 0.05-3.75 0.05-1.25 0025-0375 Liberia 990718—1-1 8 <1 7 <1 <1 990718-1-3 7 <1 5 2 <1 Size (mm) 0.05-3.625 0.075-1.5 0.025-1.875 O.125-4.5 0.025—1.25 Pijije 010627-1a 6 1 1 2 <1 010627-1c 20 <1 6 1 <1 010629-1c 15 <1 7 10 3 040706-3e 10 5 5 <1 040708-2a 4O 1O 1 1 040708-6d 10 5 2 5 1 010629-1a 15 <1 2 3 1 Size (mm) 0.05-5.0 0.175-1.5 0.05-2.5 0.075-3.75 0.025-0.75 Salitral East 040706-7f 5 4 «1 1 1 040707-2d 5 2 <1 <1 1 040707-2j 5 2 <1 1 Size (mm) 0.07525 0.07520 0.05-0.875 0.25-3.375 0.025-0.75 89 Table 2 cont. Unit! Sample Plagioclase Am phibole Biotite Quartz Opaques Modal % Modal % Modal % Modal % Modal % Santa Fe-Iow 990718-129 6 2 <1 040706-1a 15 2 <1 040706o1m 15 2 1 040706-2a 10 1 1 040707-2a 15 2 1 1 Size (mm) 0.025-2.5 0.125-2.5 0.025-0.5 Santa Fe—hm O40706-3a 5 «1 1 2 <1 040707-8f 5 <1 2 3 1 O10629-21f 7 2 <1 010629-219 3 «1 2 2 <1 Size (mm) 0.05-3.75 0.15-1.625 0.125-2.125 0.25-5.0 0.025-06 Green Layer 040706-1j 7 2 1 040707-3c 7 4 1 040708-5a 5 <1 1 Size (mm) 0.25-4.0 0.25-2.75 0.025-0.5 9O found throughout the sample collection (Figures 13 and 14). Plagioclase and quartz are typically the minerals displaying these textures; however, some amphibole grains display a “brush-like” texture that may be related to disequilibrium or a result of phenocryst dehydration during the eruption (Figure 14b). Although the petrography of the seven units is similar, meaningful variations among units do exist. The size, distribution (i.e. glomeroporphytic clots, bi-modal), and modal abundance of minerals and groundmass are features that differ between units. Most notably, biotite and quartz are only present in pumice fragments with $02 2 72 wt.%. Mineral distribution also varies considerably. Bi-modal size distributions of plagioclase and amphibole are observed in samples from the Green Layer and Virginia units. Some samples have glomeroporphorytic clots of several or all of the primary minerals present (Figure 14b). Another distinct difference is the presence of both dark and light colored glass, found in the Green layer, Santa Fe-high, Buena Vista-low, and Pijije units (Figure 15). 3. Mineral composition Individual mineral phase and glass chemistry of eighteen samples representing all of the seven units and sub-groups are provided in Table 3. Major element data are normalized to 100% and given in wt.% oxides. 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The Green layer represents the unit with the highest anorthite content (65%) in addition to having the widest compositional range (65-3 7% An; normal zoning). The plagioclase grains from the Santa F e-low are also normally zoned with a range of 5 7-3 7% An. Santa Fe-high plagioclase samples display normal zoning (3 7-28% An) with core anorthite contents similar to the rim value of the Santa F e-low plagioclase. The Salitral East plagioclases are normally zoned, with An ranging from 44-3 2%. The only unit that has plagioclase grains with clear reverse zoning is Virginia, the An ranges from 42 in the core to 52% in the inner rim, with a slight dr0p to 46% An at the outer rim. However, Virginia also has plagioclase with no zoning at ~50% An. Other units (Pijije, Liberia, Santa Fe-high) show small compositional variations from core to rim in the plagioclase grains and also represent the units with lowest anorthite content (3 2-25% An). The Buena Vista-high plagioclases display oscillatory zoning fluctuating between 30 and 44 An%. Plagioclase grains from the Buena Vista-low were not analyzed. Plagioclases are sensitive indicators of melt composition, and any changes that occur throughout the melt evolution are recorded in the mineral growth. Volcanic rocks typically exhibit plagioclase with oscillatory zoning (i.e. Anderson, 1984; Kuritani, 1998; Ginibre et al., 2002; Halama et al., 2002). Although there are seven units defined based on trace element ratios, there is considerable compositional overlap among plagioclase core and rims from several different units (Figure 16). 131 0.8 0.0.0 00030.0 .x. 0.0.0 0020 0 00 000.00 0.000050. 60.00 000m .9003 0020:0000 000.0 0>00 00.0.00 0.05 0005 05 200 .0000 $00 2 00.8 00000 00 00.0 00 .020 0500-0 .0002. 00.006 :0 .00m _0.0__0w 000 00.0.. 000.0 00.000 0003 26.0.... 203 00... 00.0.0, 00.00 00023 090-0... 0.000 000 .0...... .0000... 00. 000. 0.< 00.00... 0< 0. .000... 0.0 500 00.000 000.05. 505 00.05 00 :03 00 00.000 >00 00 000000 0000000000 000 0.0: 0.0.0..> 000 000000., 0..... 0..; ..0< o000.00. 0... 2 0.8 0.0.. 0.000 ..0 0.0 000.0200... 0.0.0 0000.0. 00.0-00 0.000 000 .0...... .0000: 000 .2 0.00.0 02 00 00 00 00 o 0 ~ 0 . . q — 1 0 0 0 - - 00 o o o - .. 90 0000.0. .- . om - 0......0 - s b 0 0 _ L _ p 0 . _ 00v 050 0.0..— 000006 00 02 00 00 00 00 0 fl 0 u Q ~ 0 1 . . 0 0 - 00 0 @ ad a G 4 T <( m Hm @ @ mov $00. 1 . co - 090-0005 0005 . 00 — p — P L — p p p 0 SP 0000 so: mop—3mg o\o OOw on OO O? ON O l q 0 0 0 0 . 0 O _ _ -ON 0 00 o 0 00.0... ..OO “mam _m.£_mw - 00 — p p p p — p p p b 8F 0.00 so: 00C0~m=u o\o OO_. OO OO O? ON O O _ 0 0 0 . _ . q q 0‘ -ON + +OV + + + .0 + + + + .0 + 4 005‘ ..OO 0.0.95 .8 — p p _ 0 — p b 0 p 00F 0.8 Eat 0000006 00 OO—- 8 8 O? ON O O _ q 0 0 0 _ J l 0 0 ON .9 O? a. $50 OO v 00>0._ 000.0 00 — L! P b p r p 0 p — 8F 0500 ED: 8CN~£U o\o 8.. on oo 90 cm 0 O _ 0 0 . 0 q 0 j . . #00 i a. .1 00 .v 0\0:< row O 0“. 0000.0, 0 _ r _ _ _ _ _ _ _ 7 co.- 0500 50.; Guzmamfi 0A. 8.. on OO O? ON O O _ 0 . 0 0 — . 0 . 0 i ON U D a O? $c< . O0 0000: :0 if r 0 0 P _ 0 L 0 0 GOP 132 In particular, the sodic rim (38% An) of the Santa Fe-low is within analytical error (010% of the actual value) of the Santa F e-high core (36% An). Also of note is the composition of the Salitral East plagioclase core, (44% An) which falls within the range (5 7-3 7% An) of the Santa Fe-low plagioclase. Trace elements Barium (Ba) and Strontium (sf) have a high partition coefficient with respect to plagioclase and provide strong additional evidence for a co-genetic relationship among evolving melts at various stages. Figure 17 shows the Ba/Sr overlap among units (Santa Fe-low, Green Layer, Salitral East, Virginia, Buena Vista-high), with lower Ba/ Sr ratios, whereas Liberia and Santa Fe-high have a higher Ba/Sr ratio. 3. 2 Amphibole Two distinct amphibole groups (high/low-Mg) have been identified using petrographic analyses and EMPA analyses. These two groups are identified by differences in interference colors and pleochroism using a polarized microscope and distinct major-trace element groupings (Figure 18). Several of the trace elements display variations consistent with the two groups. Notably the Nb and Dy are found in two distinct concentrations, high in the low-Mg amphiboles and low in the high-Mg amphiboles. All other trace elements analyzed show overlap between the two types of amphibole. High-Mg amphibole are found in the Virginia, Santa F e-low, Green Layer and low-Mg amphibole are found in the Virginia, Santa F e-high, Green Layer, Pijije, Salitral East, Buena Vista-high/low, and Liberia. 133 .0E0 000 00.00 000.200 00..0>o 0.00.00.0000 >0.00.0 00.0.5 0.0.> 000:0 000 0.0.0.5 ..00m. .0....0m A2000. 26.-0n. 0.00m ..0>0.. 000.0 00. 0000.00. 000.. .026. 00 .. 00.0.0. 00.0.0“. 0.00m 000 0000... 00. 0000.00. 000.0 .000... 00 0. 0.0080000 00. ..o 0... o. 0.00 E00 .000.>0 0.0 0000.. 0.0.0000 0.5... .0000 .0 0000098 00. 0..; 0.00 002000.00. 0.0 000: ..< 0.0080000 00032000 00. .2 .20 000.0. .0> .900 .t. 0.00.”. 0000 000.0 0.0.0 .200 10.0 05.0 20.0 L . . _ o 2.0.... 0.000 + .\ + ti o 4 0.3.. .u -. N .mfim .-. .0. .0>0.. 000.0 0 a 0. 0.000 0 o .000 0.000 - 00.0.0“. 0.000 - 0 a a 0000.. 0.. + 0.0.0.5 0.0...000000 00.0 { Q -m«m_> mcmam _ _ 0 _ v 0.00 0..”. 0.0E0w 134 .>.0>..00000. 0.00.0080 0.2-26. 000 0.00.0900 0.2-00.0 0.0.000 0000.0 000.0 00.0 0". 0.00m 000 .50. -0“. 0.00m 00 ... 0.00.0900 0.2.26. 00. ...00 0.0.08 000 00.000200. 0.00 0.0 ..0: 0.0.> 00000 00. 0.0..; 0000.0 000.0 00.0 000 32 00. .00.. 000000 0000 0 .3 000.000 0.0 00.00.0000 0.2.26. .00._ 0000 000.0 0 00 000.000 0.0 00.00.0080 0.2-00.1 .08. 00. 0. 00.00.0080 0.2.30. 000 00.0 00:00. 0.0 0000 .. .0.0000.=00..0.0 0.00.0 0.0 0000.0 0.00.00.00 .00..0.0 02F 0.00.0050 00. .0. 0E0.00.0 :0..0..0> .00....0.0 000.. 000 .o._0.2 .0. 0.00.... m0 ov J00 on O V cm I ON 0* lYfl co co. l_l l #1 l l l I J l IITfTI ON? 0-. 0.0.0.5 + .000 0.000 0 .52-0.0.> 00030 d 00.0-0.05 00000 < .0>0. 000.0 .0. 0.0.0 0 00.0.0. 0.000 i 0000... n. 30.0. 0.000 a 00.0 N0.0 om mm on 00 000 on no on 00 000 0 . 00 H . . 0. .1 u 0 . ------ 00.. - 00 .6 n. --- 1. 0. 02 0 .. A. . H .000 0-..... 0 fl " 1T \ss I. up *+\\\\ I. ...0? E... - 00 ..- ,- - -.. 0. . . . O? r . p . 1 ON N0.0 N0.0 om mm on 00 000 ow mm on 00 00 i W q d . 1 O . 0.0.0 H W. .h m n H - . 0. .r --..--- 1.0.000 - ------- X 00.2 n Ki? 0.... U . gun-0 n -------- H 0 t ----- on I J 0. . 0 0 I . P 0 .- ON - _ . on. 135 3.3 Biotite Maj or element data for biotite are displayed in variation diagrams with respect to Si02 (Figure 19). The biotite analyzed represent four of the five units that contain biotite. Pijije and Liberia biotites have intermediate FeO and MgO content relative to the Santa Fe-high and Buena Vista-high. The Santa Fe-high has higher FeO and lower MgO, while the Buena Vista-high has lower FeO and higher MgO than the Pijij e/Liberia. Trace element data for the biotite grains was not acquired. 3.4 Glass Glass chemistry for the pumice samples includes all of the major elements (Figure 20) and select trace element analyses (Figure 21). As a whole, the major elements of the glasses display a linear relationship with an increase in SiOz (Figure 20). The glass analyses can be divided into two groups: low-silica (<76.5 wt.%) and high-silica (>76.5 wt.%). The low silica group is represented by samples fiom the Green layer, Santa F e- low, and Virginia. The high silica group is represented by samples from Santa Fe- low/high, Salitral East, Pijije, Liberia, and Buena Vista-high. The units within these two groups also correspond to the low and high-silica groups identified by bulk geochemistry with the exception of the Santa Fe-low unit, which is represented in both the high and low silica glass groups. Glass trace element data displayed are restricted by a lack of data for some of the representative units (Figure 21). The Green Layer, Santa F e-low/high, Salitral East, Pijije, and Liberia, when represented, display relatively similar concentrations for the trace 136 Fv ov 00.0.0. 0.000 0. 0.0.00 o 0000.. n. 00.0-0.0.> 00000 4 00.0 00 mm. .50 . q .040 .1.Hm N0 00 mm .I.va -o&é 0.600 .00; 0.va .Hmv .00N>_000 .00 0.0; .000 0.000 00. .00.. 0...0.0 0.00.0 0.0.0 00. 000. No: 000 .0002 .000. 0. .0000 0.0.0000 0.0 0.00.0 0000... 0.00.0 0.0.0 000 0000.. 00. .0 .00.000 .0002 .00“. .00—2. .00E0.0 8.00. 00. 0003.00 >000.0.0000 00.00 0. 0.00... .00N>_000 .00 0.03 0.00.0 .00m .0....0w .02600 0.0 00.0-0.0.> 00000 000 .0000: .0000 00.0.00. 0.00m 0.0.. 0.00.0 .0E0.00.0 0o...0..0> .00E0.0 .200. 0.00.0 .0. 0.00.... .0 av . 00 VF 00:. oo o l m. - mw or 00 00 00 mm m. n. 000.... o o 1 mp mp 00... 002 we 0 00 0.0 00 mm or we 00 mm. 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I o 4 4 1 .000. +0. 0. 0 O + + . 0.0 4 0.70000. 0 0 ++ + . no + ++ + p h p — '0 p . p _ “.0 b . p r N 138 an 0.00 0.000: .0 0.00. 0. 000 000.000 00.090 000.. 00. .0 0000 .0. 00.000050. .00 0.0 0..:0 00. .0 =< 0.005000 00.050 000.205 00.00.00 .0 0.0.0000 0006 00. 0030.000 0000.000 :0..0..0> 00.000 000.... .3 0.00.0. mu 0....0 o .000. 000.0 .0. 0000.. 0 00.0.0". 0.000 .1 0.0.0.5 + 30.00. 0.000 00 00.00.05 00000 4 .000 0.000 0 00.0 00.0 00 R 00 00 £0 00 00 t . 00 00 £0 0 o . . _ . 0 6. 100.0. . .000 000. + n04 + - 0 1 F o + 0 + - 0. I 1 N 02 0._ 1+. - 1 00. 1 + - 0 4 4 p p p — V _ _ _ on m N _ _ 0.0 0. t 0.000 00 £ . 00 00 k 00 £0 q 4 . q V0 1 . 4 gq a fl 1 1 0 1 n H 1 1 0.0 w 1. 00 I + 1 H H 1 4 - 0.0 0.. w + 1. 00. .w 11 I 0.0 w H 1 1 00. .. + 1 N— n H . p _ 1T _ I . . _ 1 SN 0x. 00.0 00 t. 00 00 £ q d fl ~ 0 hr 0 1 - F 1 >0 1 + 1 N 4 p _ p — m N _ 0.. 00 R 0.0 00 00 £0 H u &— q a — U .1 1. 000 w 11 08. 00 ,. 1. ..1 + 11 000. 1 p p . — 1 OSN 139 elements analyzed. However, the Virginia and Buena Vista-high units display higher concentrations of each of the trace elements shown. 140 VI. DISCUSSION 1. Origin of silicic magma: Partial melting/ extreme fiactional crystallization of calc- alkaline andesite A review of experimental studies (Patino Douce and McCarthy, 1998; Patino Douce, 1999) concluded that generation of silicic magmas with high KzO/Nazo in subduction zone environments is not feasible through fractional crystallization or partial melting of a low-K basaltic source rock. More recently, Sisson et al. (2005) present results from an experimental study supporting a process of either a low degree of partial melting or a high degree of fractional crystallization of high K20/Na20 basalts could produce the high KZO/NaZO silicic melts. Tamuri and Tatsumi (2002) proposed a model to explain the origin of silicic melts in arc settings based on petrologic and geochemical evidence. A mantle-derived intermediate melt, hydrous magnesian andesite in composition, is generated at the slab- mantle interface. This intermediate hydrous melt at the base of the crust then ascends to shallower depths where it stalls and crystallizes as it reaches a buoyant equilibrium. Dehydration melting of this intermediate, calc-alkaline andesite could produce partial melts of silicic magma compositions similar to those found in this study. An alternative to melting a solidified caJc-alkaline andesite is extraction of the silicic interstitial liquid from a medium to high-K20 basaltic melt that undergoes a high degree of fractional crystallization or partial melting of a crystalline medium to high-K20 basalt (Sisson et al., 2005} Geochemical evidence from the Guachipelin volcanic suite is consistent with the results from Tamura and Tatsumi (2002) and Sisson et al. (2005). First, Tamura and 141 Tatsumi (2002) define the intermediate crystalline bodies that have stalled in the crust as hydrous and calc-alkaline in composition. A depletion of middle rare-earth elements (MREE) in all samples, with the exception of the Green Layer, indicates a hydrous source based on the presence of residual amphibole (Figure 22). The relative enrichment in MREE of the Green Layer unit could be a result of a higher degree of partial melting that consumed the residual amphibole of the source rock, increasing the MREE. In addition, the patterns in Figure 9 clearly relate the silicic volcanic products to processes related to are magmatism. Second, the high alkali content of these magmas is also consistent with Sisson et al. (2005) experimental results indicating partial melting of amphibole rich calc- alkaline sources could produce these silicic melts. The Guachipelin suite is within this range of elevated alkalies shown in Figure 23. The experiments of Sisson et al. (2005) involved melting of gabbros with medium to high-K content similar to those found in basaltic lavas from Costa Rica. In addition, the starting products Sisson et al. (2005) used also contained amphibole, which is a proposed component of the Guachipelin source rocks. Although the Guachipelin ash-flow sheets may share similar types of source, distinct trace element variations exist among the separate ash-flow sheets implying that the sources were not identical. It is therefore necessary to further evaluate possible processes of magma differentiation. The following are several of these processes that will be evaluated: 1) different degrees of partial melting of a single source, 2) partial melting of several distinct sources, 3) fractional crystallization, and 4) assimilation. Before these processes are evaluated, the behavior of the HF SE, used to differentiate between chemically distinct units, will be addressed. 142 .000. 00000000: 000 0:0 .0 0:_0> 0.000000 0. 00_.0N__00000 00.0000 2 .0000000 00... 00500 00. 0_ 20020.00 >0 mum—2 00. .0 00.00.000.000 .0 .3000 00. 00 0.000 F v 23.2.5 .0 0029 0.05 00.9000 000000. .30. 000: 000 0.0 000: 0.0 0. 00.00. 0.0. 000.2 0_ 000000> 05 00000020 .20 .mm 0500 23.2.5 000.00 000.0 .0. 000.00 0.000 a. fi 2 z 32.00 0.000 0. Av 0.0 0._ .000 00:00 0 an". 0.00 o 1 an. 0000: D ”no 00605 + 30.0.05 000.5 4 0020.05 0:000 4 0 on 143 .2< 000.0002 00000 0.000 05 EB. .3300 A 000. 020.000 000000 2050 00. 00000000000 00__ 000000 0.000.000. 000000 2050 0__00_00000 00. 0.000000. 00.0 000: _00000_0 00m .6008 ._0 .0 00005 .0._0000..v_ 090 .0 0020.0 E00. 0.300. _0.00_0000x0 0.0000000. 00.0 00000 02m 0000.0 00 ._0 .0 _000> .00.. 00500.2 .mN 00090 0002 + 000. O ‘- In C Illlllrl l llllilll l I l ozemozx JJlllll l ‘— l I \llll Tfl 144 2. Sources (HFSE: Nb, Ta, Zr, Hf systematics) Incompatible trace element ratios are used to differentiate between chemically distinct magma batches. The trace element behavior is controlled by the composition of the source, distribution coefficient, and the degree of melting. Therefore, the individual element contributions from possible subduction zone components (i.e. slab melting) could influence the overall mass flux and/ or partitioning into phases prior to eruption. High field strength elements (HF SE: Nb, Ta, Zr, and Hf) are of particular interest in studies involving subduction zone magmatism because of their different behavior in this setting compared to other settings. HF SE are characteristically depleted relative to REE and large ion lithophile elements (LILE) in magmas fi'om subduction zone settings. This depletion is related to the mass flux processes associated with the subducting slab to the mantle (Munker et al., 2004). Yet, their behavior in this tectonic setting is still not well understood (i.e. Barth et al., 2000; Munker et al., 2004; Schmidt et al., 2004). It has been shown using the Nb/T a ratio cumulative frequency plots for the Guachipelin pumice samples that discrete heterogeneities occur within this suite of volcanic deposits (Figure 11). Distinct breaks and/ or differences in the slope of the sample distribution indicate for the most part that a process other than fractional crystallization has governed the chemical differentiation among units (Figure 11a). Specifically in the case of Nb/T a, the distinct variation displayed among units is not only abrupt, but systematic with respect to Ta (Figure 11c). This systematic control over the ratio by Ta could be a result of a common single phase partitioning within each unit. The . compositional overlap among several units displayed by Zr/I-lf (Figure 11b), could be a result of chemical “overprinting” by some late stage process such as mixing or 145 assimilation. The distribution coefficients, crystallization history, and timing of the mixing events relative to the mineral crystallization could influence the degree of overlap found among units. Therefore, other trace element ratios may not reflect the differences among the sources of units. This requires specific attention be given to the behavior of Nb and Ta in determining the differentiation processes. There are several different stages involved in magma generation in subduction zones that may affect the HF SE composition of the igneous products: slab dehydration, slab melting, and mantle composition. First, fractionation of the HF SE through slab melting and dehydration at the slab-mantle wedge interface is considered. Munker et al. (2004) and Schmidt et al. (2004) have suggested that residual rutile in the slab could account for variations in MN“ a. However, these samples show no correlation between ratios used to infer slab melt (Sr/Y) and Nb/T a variation (Figure 24a). Nb is more incompatible than Ta during an ilmenite-, clinopyroxene-, and rutile- controlled melting process, which would cause variations in mantle wedge depletions. Therefore, a correlation of Nb/T a with other mantle wedge depletion parameters (Zr/Nb, Zr/Hf, Lu/ Hf) is expected (Munker et al., 2004). Yet these magmas show no correlation with mantle wedge depletion parameters (Figure 24b). In addition, with respect to slab dehydration in fluid dominated subduction zone environments, Nb-Ta are thought to otherwise behave conservatively (Elliot et al., 1997). Consequently, partitioning of these elements during a later stage of melt evolution is required to account for the trace element variations of the Guachipelin volcanic suite. Further work regarding HFSE partitioning suggests crustal level differentiation could be responsible for the Nb/Ta variations (Barth et al., 2000). Barth et al. (2000) 146 .000. 0 ...02 00. 00500000 .00 0.0 0000.000 0000.5 0000.0 .0 000.000 0.00..0> 0.000000 0.0.0 .203000 .00. 020M 000 01.0.. ..10N 0.0. 0.0.00.0.00 0000.000 0000.0 .00.0 000 0 ...02 0003.00 0000.0..00 00000 0 .0 0.00. 00. 00.0000... .0 5.9000000. 000.000 090 00.0 000 .00000E00 00000.. 0000000 00 .0 000000.000 .0 20.00.00. 00 0000 00 000 .13.. 000 .10N 000.000 00.0 00.0 0..; 0000.0..00 00 03000 0 ...02 000. .5020 030000.000. >02 .>..w 00.0 0.0.> 000.000. 0.0.0000 0.00? 0000.0 00. 0..; ._00. 00.0.0 00000.0.0. A0 030$ ._0 ..0 .0002). 0.0.. 000.005. 0.000 0.00.“. Nd «d 0.0 or 00.32 cm ow or 0.0.02 on on .0 w 0.0 A“ .13.. OF 0:02 on on 147 propose a process of intracrustal differentiation of basaltic magma to form evolved melts. The HFSE differences among the calc-alkaline sources could be a result of the presence of several key minerals. These minerals determine the final mineral-melt partitioning and therefore the composition of any liquid produced in subsequent melting events. In particular, the following minerals fractionate Nb and Ta to different degrees: magnetite (Dm/DT,l ca. 0.7-0.9), amphibole (DNb/DTa ca. 0.7-1.9), ilmenite (DNt/D-ra ca. 0.7-0.9), and clinopyroxene (DNb/DTa ca. 0.3-1.0) (Munker et al., 2004). These minerals are found in peridotite, basalts, eclogites, or amphibolities. The presence of Mg-amphibole in the source could decrease the Nb/T a ratio in the melt, accounting for the melts with distinct Nb/T a ratios below the chondritic ratio of 19900.6 (Munker et al., 2004). All of the units have ratios lower than chondrite with the exception of the Green Layer. In contrast, the presence of ilmenite and/ or clinopyroxene increases the melt in Nb/T a with respect to chondrite. Zr/Hf ratios in the melts are controlled primarily by magnetite (1)2me ca. 1.0- 2.3), pyroxenes (Db/Dy“ ca. 0.45-0.98), and amphibole (Db/Dar ca. 0.3-0.6) (Munker et al., 2004). The presence of magnetite in the source would decrease the Zr/Hf in the melt, whereas pyroxenes and amphibole would increase the ratio. It has now been shown that the differences in HFSE can be accounted for by different mineral compositions of the sources. Although we have determined the existence of seven distinct magmas, this does not necessarily require seven sources. These magmas could be related by a high degree of fractional crystallization Sisson et al. (2005) of a single source rock. However, considering that in order to maintain the systematic increase in Ta among units, as the Nb/T a decreases, a single source must 148 produce melts progressively enriched in Ta, it is expected that the sequence of eruptions would display this change. This is not supported by the depositional sequence in this study or a relationship between Nb/Ta and Si02 (Figure 25), An oxygen isotope study of ignimbrites from Costa Rica by Eaton (2004), concluded that major element correlations with 5180 were not consistent with crystal fractionation. Instead he postulated that variations in the 5180 might be explained by assimilation of crustal rocks that have been affected by surface waters low in 5'80. It is important to note that at most three of the seven units described in this study were represented in that interpretation. Nevertheless, there is no evidence to support fractional crystallization (F C) as the primary process of differentiation relating these magmas. Eaton (2004) also demonstrated that the Guanacaste region, that includes the Guachipelin, displayed lower 5180 values than the rest of Costa Rica (Figure 26). An alternative process to fractional crystallization is different degrees of partial melting of a single source rock. However, as a whole these units lack any significant difference in the degree of partial melting (Figure 22), assuming amphibole is in the source for all of the magmas. There is no evidence of assimilation of the Caribbean Large Igneous Province (CLIP), the multi-component crustal material these magmas intrude. Mineral composition analyses of over ninety pumice samples from the Guachipelin units alone revealed no evidence of xenoliths or xenocrysts. Second, the bulk geochemistry does not support the assimilation of a more mafic component that may have been completely melted during an event. Furthermore, multiple trials using PVA on data from Hauff et al. (2000) that 149 included samples of each of the individual components of the CLIP, failed to show any geochemical relationship between the pumice from the Guachipelin and the CLIP. 150 .000. 0 ...02 0... 05:00:00 .00 0. .0.00.0. 0.02:0 0 .0 00..0~.__0.0>.0 .000..00.. .00. 0000000... NOE 000.0> 000. 0 ...Bz .0 E0.00.0 :0..0..0> ...N 0.00.". N90 8 m. o. 00 .000.. 000.0 I... 0....02 82.0. 0.50 .1 30.0”. 0.000 a .000 .9000 o 0...... o 0:8: a 0.595 + 30.0.05 0003 Q 52.905 08:0 4 on 151 .30. 2000.00.000 0.0 25.00.5000 0.... 2.0050000. 0.00000000 00. 002000 0.2.0.000000. 00. 0.0.. 020 axed 20.00.06.000 .0 0.0 000.0 0000.00. ._0.0>0 00 0. 0.0... 00000.? .300. 00.0w 0.0.“. .00 0.00.“. .0.... 0.0 000.0 0000.05 000. 000.. 000 000 com com on» can one _ _ .1 _ m . — _ - o 8E 0.80 W .. m . .. .. ._. _ m a... m x .M ) .. m H - 0 .w. H 9 m ( a. . m . 0.. w u w m - w H m M 0000.022 ” m _ _ . . . _ _ _ _ m 0.000.000 00.0.00 00.0 ...0; 00A. 20 c8082. .0050 * 0.000.000 00.0.00 0.05 $.05 00A. 5.0020006 Mm 152 3. Limited fractional crystallization and melt segregation Although the process of fractional crystallization (FC) fails to account for the chemical variation among the units, multiple linear regression modeling supports limited FC during the evolution of the Santa Fe unit from the low to high silica group (Figure 27). The presence of the compositional gap between the two Santa Fe groups (Figure 7) and distinct differences in the degree of crystallinity requires these deposits to follow separate evolutionary trends. The two sub-groups Santa F e-low and -high were originally defined as one unit based on the similar Nb/T a ratios 15.22 and 15.20, respectively, and the fact that they occur in stratigraphic contact with one another. Therefore, explaining the compositional gap by different sources is rejected. Major elements from the Santa Fe vary systematically, decreasing in MgO, R203, and CaO with an increase in SiOz and are consistent with PC trends. Several different parent/daughter combinations were used in the model to test F C, first within the Santa Fe-low, then from the low to an intermediate, and finally to the Santa Fe-high (Figure 27a). Table 4 shows the results of this three part model. The sum of the squares (2r2) of the residual provides a measure of the similarity between measured and theoretical chemical parameters tested. The 0.023 and 0.05 Zr2 residual determined in this modeling is well below acceptable limits that other workers have established. In addition, the liquid/ melt predictions correspond well with the actual pumice crystallinity and mineral abundances. Theoretical predictions of trace element compositions for the daughter were estimated using a combination of partition coefficients from Rollison (1993) and the GERM on-line database (http://www.earthref.org/GERlVI/index.html?main.htm). Figure 27b displays a comparison of the trace element concentrations of the predicted daughter 153 30>> 31.09.8020 5.000300.— v. 02 D 5.09.50 q 0 - q < - ~ - q - - - - - - - - - n q - lllllll IT llllll‘l 1 8.03.00 0 8288 n. o awhw h-—-—h—---—-_- --------u<-qq llllll l I lllllll I lllllll I I lllllll I I 020028 0 0020000 0 jjm --0 [LI l- U) [Illllll I IIIIITTT I 85800 4 002030 Q < mmhm -—»-—-—...-..h—_h—. “ll Illllll I 0.. 00.. 80 F o. oo. 08 ‘— o. 00. 000 . enuew '90wa noon anuaw enmumd/ H908 SIIUBW shillwfld/ X308 .0..00 .000.>.05 0.0000. 0. 0000 00.000 0...0 .00.0.0000 .00 0.0 0.00.020 .0200 0. 0000 0.00030 "0.02 00.0 0000 .0. 0000.. .000.0.0 000.. 00.0.0200 000 0020000 00. 000000.00 0.00.020 .00.0m 3 200.833 00.0030 01.08:. 0:20.. 00... 0. .50. 0.0.. ..00 0". 0.00m 00. 50...: 000 .000...000.000 00. 000.00 00.00008 05.0000. 0.000000. 0 8.0 200-883 .2098 0.1883 0020.. 0.00.00 0“. 0.00m 0.2000090. 00 0. 00.00.00 30.0“. 0.00m 00290 .000. 00. .0 000 E0.. .0000. 00. 03000 0 00.0 20.1883 00.00000 51885 000.00. 32.0”. 0.00m 00. 50...: 05.0000. 00. 0.000000. < 005 .o-< 0005 .0. 00.50.00 00. 0.00.00. 0. 0000 03000 .so..0> 00.0-0“. 0.00m 000 32-0... 0.00m 00. 0003.00 0“. 05.00. 0. .0005. 002000.00. .000.. 0.00.08 00.00 05.0000. .00.. 00..0~.__0.0>.0 000000.”. .0 0.00m 0.00.”. N0.0 . 0 mm W 8 .0. .5 0.0 u - Nd . - v.0 . - 0.0 - - 0.0 .0000. 00030.80»... .0.—0000.”. .0 . . S ~05 154 Table 4 Multiple linear regressions STEP A PARENT 0106304h DAUGHTER 010630-4a % Min/rock 1 .7 Homblende 5.0 Plagioclase 0.2 ilmenite 0.8 Magnetite 0.923 Liquid remaining Sum of the squares of the residual = 0. 05 Analyte DauLhter Obs: 0106304h Cale: 010630-4h Residual SiO, 70.32 68.43 68.41 0.01 TiOz 0.45 0.57 0.57 O Al203 15.88 16.17 16.15 0.01 FeO 3.07 4.04 4.04 O MnO 0.07 0.11 0.09 0.02 M90 0.74 1.13 1.13 O CaO 2.8 3.13 3.21 0.08 Map 2.9 3.06 2.91 0.15 K20 3.73 3.31 - 3.45 0.14 P205 0.03 0.03 0.03 0 Prediction based on distribution coefficients RB 61.9 58 58.4 0.47 SR 347 367.5 402.5 34.98 ZR 207.7 210.8 195.7 15.1 BA 1621.8 1399.2 1543.5 144.31 LA 27.8 36.7 26.8 9.91 CE 58.2 63.2 56.3 6.85 ND 24.7 36.2 24.3 11.9 SM 5.14 7.33 5.1 2.23 EU 1.31 1.71 1.44 0.26 TB 0.66 1.02 0.63 0.39 DY 3.66 5.69 4.32 1.36 ER 2.33 3.45 2.66 0.78 YB 2.44 3.69 2.37 1.32 LU 0.39 0.57 0.38 0.19 HF 4.15 4.62 3.91 0.71 TA 0.63 0.58 0.76 0.18 TH 5.29 5.37 4.98 0.39 U 3.79 3.12 3.54 0.42 155 Table 4 cont STEP 8 PARENT 01063040 DAUGHTER 040707-2a % Min/rock 2.2 Homblende 6.4 Plagioclase 0.3 ilmenite 0.9 Magnetite 90.2 Liquid remaining Sum of the squares of the residual = 0. 09 Analyte Daughter Obs: 01063040 Cale: 0106304e Residual Si02 70.89 68.13 68.36 0.09 TiOz 0.34 0.51 0.53 0.02 Al203 17.69 18.11 18.03 0.04 FeO 2.5 3.48 3.5 0.02 MnO 0.09 0.07 0.1 0.03 M90 0.38 0.82 0.75 0.07 CaO 2.24 2.92 3.05 0.13 NaZO 2.32 2.66 2.43 0.23 K20 3.53 3.26 ~ 3.21 0.05 P205 0.02 0.03 0.02 0.01 Prediction based on distribution coefficients RB 0.29 56.5 60.6 4.05 SR 2.87 356.9 409.3 52.4 ZR 0.27 219.9 166 54 BA 0.39 1457.5 1607.8 150.3 LA 0.55 25.1 31.9 6.8 CE 0.65 50.8 58.6 7.87 ND 1.08 20.1 24.4 4.31 SM 1.31 4.04 3.83 0.2 EU 2.32 1.18 1.18 0 TB 0.4 0.6 0.41 0.2 DY 1.62 3.35 2.54 0.81 ER 1.41 2.17 1.21 0.96 YB 1.33 2.59 1.84 0.75 LU 1.21 0.41 0.26 0.16 HF 0.25 4.71 3.26 1.45 TA 0.32 0.69 0.74 0.05 TH 0.3 5.82 8.51 2.68 U 0.16 3.53 3.54 0.01 156 Table 4 cont. STEP C PARENT 0106304h DAUGHTER 040708-6A % Min/rock 4.2 Homblende 1 1.2 Plagioclase 0.3 ilmenite 2.2 Magnetite 82.1 Liquid remaining Sum of the squares of the residual = 0. 02 Analyte Daughter Obs: 0106304h Calc: 010630-4h Residual SiOz 73.96 68.44 68.57 0.05 Ti02 0.26 0.57 0.58 0.01 N203 15.06 16.17 16.04 0.07 FeO 1.64 4.04 4.05 0.01 MnO 0.07 0.11 0.1 0.01 M90 0.39 1.13 1.08 0.04 030 1.65 3.13 3.21 0.07 Na20 3.01 3.05 3.07 0.02 K20 3.94 3.32 3.28 0.04 P205 0.02 0.03 0.02 0.01 Prediction based on distribution coefficients RB 0.28 58 76.7 18.72 SR 2.76 367.6 339.9 27.7 ZR 0.27 210.9 115.4 95.5 BA 0.38 1399.3 1566.5 167.22 LA 0.47 36.7 22.3 14.4 CE 0.51 63.2 42 21.2 ND 0.73 36.2 14.8 21.4 SM 0.87 7.33 2.18 5.15 EU 2.15 1.71 0.73 0.98 TB 0.36 1.02 0.27 0.75 DY - 3.17 5.69 2.63 3.06 ER 2.82 3.45 1.08 2.37 YB 0.6 3.69 1.45 2.24 LU 0.58 0.57 0.22 0.35 HF 0.22 4.62 2.41 2.22 TA 2.04 0.58 0.73 0.14 TH 0.17 5.37 7.81 2.43 U 0.11 3.12 3.75 0.63 157 and the actual pumice sample for steps A-C. Steps A and B display a good correlation between the observed and calculated trace element quantities as the melt fractionates out key minerals: amphibole, plagioclase, ilmenite, and magnetite. The lack of a good correlation between some of the M- HREE in Step C could be the result fractionation of biotite, quartz, zircon, or apatite related to the Santa Fe-high magma. Trace element partitioning in these minerals were not considered in this model due to the lack of mineral composition data available. The compositional gap between the Santa Fe-low and high requires fractional crystallization to occur with melt segregation/ extraction from the crystallizing magma. The higher degree of crystallinity of the low-silica Santa Fe group (up to 17%) could represent a longer residence time in a shallow magma chamber with subsequent extractions of interstitial melt to produce two other identified units. First, Step A involves the fractional crystallization within the Santa Fe-low magma. Second, the Salitral East, a hybrid magma, is proposed to be the product of melt extraction from the evolving Santa Fe-low initial melt at some intermediate point of crystallization. This is represented by Step B in the multiple linear regressions in Figure 27. However, the Salitral East, which is defined as a distinct magma, also requires some process that would change the Nb/T a ratio (see section below for further explanation). Third, Step C models extraction of a melt from the Santa Fe-low magma reservoir, after the extraction of the melt involved in producing the Salitral East magma, which could produce the Santa Fe-high. This unit is characterized by a lower degree of crystallinity than the Santa F e-low (up to 10%) and the core plagioclase compositions correspond to the rim compositions of the Santa F e- low (Figure 16). 158 4. Mixing/Mingling 4.1 Geochemical and petrologic evidence The distinct geochemical variations between the Guachipelin ash-flow deposits require one or more of several magma differentiation processes. Limited fractional crystallization (FC) of the Santa Fe-low with subsequent extractions of the Salitral East and Santa F e-high magmas represents one of these processes involved in the magma evolution, but several factors limit this interpretation to only two of the seven units. First, the Santa Fe unit, including both low and high sub-groups, is defined based on having the same average Nb/T a. Crystal fractionation of amphibole, plagioclase, magnetite, ilmenite, zircon, and apatite would not change the incompatible element ratio among these samples if both elements are behaving equally incompatible with respect to the mineral-melt system. In Figure 11c it is evident that the individual Santa Fe and Salitral East units have nearly horizontal trends, indicating that the Nb and Ta are behaving equally incompatible. Second, although the Salitral East has a distinct Nb/T a ratio, the samples fall within the major element compositional gap between the Santa Fe groups and the plagioclase core compositions are within the intermediate compositional range of the Santa F e-low. However, the remaining units - defined by distinct differences in incompatible elements - require some other process to account for the chemical variations. There are both geochemical and petrologic evidence of mixing/ mingling in most of the representative ash-flow units. The geochemical evidence includes 1) the presence of two amphibole types (High and Low-Mg) in a single pumice, 2) bulk compositional overlap among units, 3) the presence of two different glass compositions in a single pumice, 4) compositional similarities of glasses between units, 5) compositional 159 similarities between plagioclase, amphibole, or biotite, 6) plagioclase with reverse and/or oscillatory zoning. Petrographic evidence includes disequilibrium textures in plagioclase and amphibole. 4.2 Polytopic vector analysis (P VA); (See appendix A for description of method) The polytopic vector analyses of pumice major and trace elements from the units, yields a basis of geochemical relationships among samples and are useful in determining the presence of mixing/ fractional crystallization trends. Data output displayed on a scatterplot matn'x show compositional trends that might occur among samples. A correlation determined by this method provides support for mixing and fiactionation processes as the primary controls in chemical differentiation. PVA mixing trends generated by analysis of all of the data are consistent with those inferred by evaluating the parallel to sub-parallel A1203 variation with increasing Si02 (Figure 28). PVA involves co-analyses of the various units that display chemical and petrologic evidence of mixing from the entire data set. Four end-members or initial melts (IM) were required to characterize all of the units. Initial melt compositions are provided in Table 5. These initial melts (IM) are compositionally similar to eruptive deposits (e. g. Santa F e-low) and are distinguished in the subsequent discussion as: IM 1, IM 2, IM 3, and 1M 4. The initial melt (IM 2) is also evolving throughout the proposed sequences of mixing. Any composition more evolved than that initial melt (IM 2) is referred to as an evolved melt (EV 2). The following mixing systems were identified using PVA on the bulk geochemical data: [M 2+EV 2 andIM1;IM2+EV2andIM3;IM2+EV2andIM4. 160 .8_E:a £595 ”@233 goes ecm moEEmm 8:55 30.2955“. Scam ”mxmtwuwm xomE o£ ho cozacoxo o5 53> .Eflmmfi co=m_.m> 9: E 305 9 .m__E_m 9m xEmE 8.9958 5 m_onE>w .v Sm. new N 2m $923 95:25.9 9: 9:59:00 can; comm 2520 muse: m 9.: 2 ecoawotoo $5 mace: 6:93 2 6:93-93 m 9: 250% 693% 0ONE, of. 6:53 3322?: some .2 232.9: .95 98 22535 9: $5359 85 E936 93.3%,: V6 2953 .mm 059“. fl. 3 mo~_< t 2 .iu o. ..I .lvd mod mo mud wvo mod x5e: «Secateuw . 88., 92.9 22.9 83,6- 12m $3.? 803 mind. 88.? 25 28d- 2.3.9 88.? 83.6. «SE 836. 88.? 8:8. 884 :6 IE nsm. «2m rzm _ accusatoow .9629?! . 161 Table 5 Initial melt commitlons from the four end member sources Includes the most evolved end member of the Santa Fe (EV-2) Analyte IM 1 IM 2 EV 2 IM 3 IM 4 SiO 2 67 66.9 76.9 67.2 71.2 TiO 2 0.537 0.645 0.0573 0.592 0.311 N203 18.8 15.7 14.1 16.9 17.1 F90 4.4 4.75 0.5 4.3 2.25 MnO 0.177 0.11 0.0389 0.135 0.0493 MgO 0.546 1.22 -0.0141 0.848 0.59 080 2.5 3.92 0.913 3.43 1.72 Na 2 O 2.38 3.49 2.52 3 2.47 K 2 O 3.37 3.02 4.68 3.24 3.99 P2 05 0.0294 0.0633 0.0128 0.0463 0.0162 Rb 68.7 41.8 105 51.3 101 Sr 355 467 153 417 254 Zr 200 253 73.2 235 173 Y 30.7 26.7 8.1 21.9 15.2 Nb 12.8 8.56 9.02 8.39 8.59 Ba 1930 1290 1900 1440 1710 La 42.4 24.9 22.5 22.8 27.5 Ce 96.6 54.2 38.9 59.1 52.9 Pr 12.2 6.36 3.52 6.32 6.05 Nd 45.9 25.2 8.93 24.6 22.3 Sm 7.6 5.39 0.341 5.4 3.87 Eu 1.52 1.55 0.147 1.57 1.05 Gd 6.89 5.26 0.509 4.75 5.57 Tb 0.817 0.777 0.0415 0.735 0.515 Dy 4.39 4.27 0.218 3.74 2.79 HO 0.707 0.942 —0.00463 0.755 0.478 Er 1.7 2.86 -0.287 2.29 1.51 Yb 1.99 3.01 0.703 2.79 2.16 Lu 0.3 0.459 0.0549 0.416 0.332 Hf 3.54 5.36 0.889 4.89 4.59 Ta 0.494 0.526 0.586 0.847 2.1 Pb 11.5 8.59 13.5 12.3 18.8 Th 8.29 3.29 9.95 4.2 8.92 162 Each of these mixing systems was evaluated in compositional space using both major and trace elements to illustrate the overlap among its constituents. The first mixing system between the IM 2+ EV 2 and IM 1 produces a modified Santa Fe-low magma (Figure 29a). This interaction is extensive and ongoing as the initial Santa Fe melt evolves by fractional crystallization (EV 2). Some Santa Fe-low and Green Layer pumice fragments exhibit similarities in: 1) major element glass chemistry (Figure 21), 2) bulk geochemistry (REE patterns, Nb/T a) (Figures 7 and 8), 3) amphibole composition (Figure 19), 4) plagioclase composition (Figure 16 and 17). Glass major element chemistry of these units shows considerable overlap (Figures 20). It is expected that sufficient mixing of the IM 2+ EV 2 with the IM 1 would elevate the Nb/T a near that of the Green Layer. This also requires a large contribution of the IM 1, which is consistent with PVA generated proportions of IM 1 contribution, up to 58% (Figure 29a). Some of the Santa Fe samples with higher than average Nb/T a ratios are found closest to the Green Layer-1M apex of the ternary mixing diagram (Figure 29a). The amphibole found in both of these units is the high-Mg type and plagioclase compositions are similar in both anorthite content and Ba/Sr trends (Figures 16-18). Disequilibrium textures in plagioclase from the Santa F e-low and Green layer and the presence of two distinct glasses in Green Layer pumice identified in petrographic analyses, suggests the mixing of melts after one or both have already begun to crystallize. The preservation of this texture in itself supports a relatively short time elapsed between mixing and eruption (N akamura, 1995). The next mixing system is between the IM 2+EV 2 and IM 3, which produces the Salitral East magma (Figure 29b). The Salitral East, Santa Fe-low, and Buena Vista-high 163 .8_E:a 595855 «:25 8298:“ coma 88.0 .8_E:Q 5mm _m=__mw ”mucoEmfi 283 :30 62:5“. 267m“. Scam ”29m 3.33 :30 .mEme “mam _g__mm 25E 9: 95:35 N s: 05 can N >m+N _2_ 65 E0: 0.309on :9: 0..: mcoEm <>m E noEEQou 22.885 92:. mczgwcoEou EEmwfi meoh 3 .8_E:a .26.. :35 8388 0.83 cone ecu ooESn 32-0“. Scam ”83m xomE :80 .mco_wmo52 Ems. 292:8 ago: mc=oeoE FE; Eofimcoo 5mg 05 E398. mace: cozmuafimbo .2282“. ._. .2. new N >m+N s: 9:290 05 meoEm <>n_ >9 cos—Egon mcoanoa m:_x_E mczgmcoEoe Swami beEm... Am .ndmN 059“. N s__ n .2. 3 NE. FE. 164 N>m E. chm—2 ._<_.:z_ >m FAME Dm>._0>w ”>mx N >m pumice fragments exhibit similarities in: 1) glass major element chemistry (Figure 20), 2) bulk geochemistry (Figures 7 and 8); not similar, but Salitral East fall in between the Santa Fe-low and Buena Vista-high, 3) amphibole composition (Figure 18), 4) plagioclase composition (Figure 16 and 17). In regards to glass, bulk geochemistry, and amphibole composition the Salitral East is compositionally more similar to the Buena Vista-high than the Santa Fe-low. However, the Salitral East plagioclase core compositions reflect initial growth within a less evolved magma (Santa F e-low) than the Buena Vista-high. This is consistent with melt extraction from the IM 2 after there has been some crystallization (Figure 27b) and subsequent mixing with a more evolved magma the IM 3. Mixing with this magma type would maintain the normal zoning and is consistent with the plagioclase trace elementtrends (Figures 16 and 17). The dominant nature of the compositional similarities between the Salitral East and Buena Vista-high pumice fragments suggests extensive input from the IM 3 rather than the 1M 2+EV 2, produced the Salitral East magma. This is also consistent with PVA mixing proportions, up to 60% of IM 3 (Figure 29b). In addition, the Salitral East pumice fragments lack any signs of compositional banding in either the hand samples or the thin sections. Therefore the subordinate IM 2 magma may have reached thermal equilibrium with the interacting IM 3. Although corroded plagioclase cores indicate chemical disequilibrium exists between the two. This supports the early growth of the plagioclase fi'om the IM 2 that came in contact with the IM 3 magma long enough to reach thermal, but not chemical, equilibrium. The evolved EV 2 and IM 1 undergo limited mixing, modifying the magmas (Figure 30a). This mixing occurs after the Santa Fe reaches the final stage of crystal 165 .8_E=a gaze“. Scam 8.8m 3.06... 33.0 new 60......3 9.3... ”moxon on... :oao .8.E:a m..._.n. ”32.0 8. :80 .259: 0......n. 2...... a... 2.8.85 w .2. a... as... N >m+~ .2. 9.. as. 8.09.6 ..o... o... meoEm <>n. .3 35:55.. 33:80... m.._x.E unambmcoEou EEmmB base... 3 .8_E:a .96.. 56.0 838.0 6.92. :30 use 8.83.. 5.5.9. Ecmw .38» 3.33 .6320 8.8.3666. 59... 6.92:... 9.6: m:_.ouoE 5.3 Emfimcoo 53 e... 2323. «use: :o..m~...3m>.o Escrow... .P .>.. can N >m.+N .2. cm>.o>o 25m... 9.. 9.8.5 <>n. .3 355.9% 22.83:. m:_x.E uc_.m..m..oEoe E9666 meoh 3 Eden 659“. N E. . fi 5. AD NE. v2. 166 E. H._.._m_>_ ..<_._._Z_ >m FIE—2 Dw>..0>w u>mv_ fractionation (Figure 27a). At this point melt is extracted from this magma body and mixes with the IM 1. The Green Layer is influenced more in this mixing system, a contributing proportion of Santa Fe up to 50% according to the PVA results. The presence of both high and low Mg- amphiboles in a single Green Layer pumice that are not found in the Santa F e-high pumice, is also consistent with these mixing proportions. High Mg-amphibole is only associated with the IM 1 and low Mg-amphibole only with the Santa F e-high, or in general the low and high - silica groups, respectively. Selected Santa Fe-high and Green Layer pumice exhibit similarities in amphibole composition (Figure 18). Petrographically these Green Layer pumice fragments also display clear evidence of both a dark and light colored glass. Similar to the good correlation between the Santa F e-low: Green Layer interaction described earlier, the Santa Fe-high with the highest Nb/T a relative to the other Santa Fe-high samples show REE patterns that are similar to the patterns for the Green Layer pumice (Figures 9 and 10). The evolved EV 2 and IM 4 mix to produce the hybrid Pijije magma (Figure 30b). The Santa Fe-high, Pijije, and Liberia pumice exhibit limited similarities in: 1) glass major and trace element chemistry (Figures 20 and 21), 2) bulk geochemistry (Figures 7 and 8), 3) amphibole major element composition (Figure 18), 4) plagioclase composition (Figures 16 and 17). In addition, the Na20 and K20 concentrations in the biotite from the Pijije fall on or between the Liberia and Santa Fe-high biotite. The final mixing relationships are between the IM 2+EV 2 and the IM 3 to produce the hybrid Virginia and subsequently the modified Buena Vista-low magmas (Figure 31a,b). The Santa Fe-low, Virginia, and Buena Vista-low exhibit similarities in: 1) glass major and trace element chemistry of the Virginia and Santa Fe-low only 167 .8.E:n. 5.22.6. 655 9.26 66.9.6... come :36 new 60.95... «.595 .3820 v.06... .8.E:.. 32-0“. Baum ”9.8m coco .35 on... .mEmmE Bo.-m.m.> acoam 9... 825:. m .2. new N .2. 9.3.06 o... 5923 9.3.2 3 .mEme «.595 .25.... 9.. 88:85 32...... 95w 9.. .o .856 .88. 9.. :85». 9.3.2 .m .2. 95 N >m+N .>.. 9..>.o>o on. 9.8.5 <>a .3 boggefiu 203.80... 9..x.E 9...m..m:oEou Edam... meo... 8 5.3m e59“. N>m n:— 168 .2. Has. 2E2. >m ”Bus. om>..o>m. N .2. u>m¥ (Figures 20 and 21), 2) bulk geochemistry (Figures 7 and 8), 3) amphibole composition (Figure 18), 4) plagioclase composition (Figures 16 and 17). This final sequence of eruptions requires the protracted existence of the IM 3 and an evolving IM 2. Key petrologic evidence that supports the mixing to produce the hybrid Virginia include the presence of oscillatory and reverse zoning in the Buena Vista-high and Virginia plagioclase phenocrysts, respectively. In addition, the high and low- Mg amphibole are found in the Virginia pumice population, but not in the same sample. Both the anorthite content of the plagioclase (up to 57% rim) and presence of the high-Mg amphibole are interpreted as the result of mixing with a less evolved magma, specifically the IM 2. 169 5. Model for the petrogenetic evolution of distinct silicic magmas The petrogenetic model is based on several co-evolutionary processes that generate chemically distinct magma batches. These processes include partial melting of four chemically distinct crystalline sources that produces the chemically distinct melts, limited fractional crystallization, and extensive mixing. Figure 32 shows that both magma fractionation and mixing were important processes in the petrogenesis of the initial melts. The multiple inputs of the initial melts in mixing events also requires a protracted residence of several of these melts. It is important to note the lack of temporal and/ or physical constraints on the initiation and residence of each of the end member melts prior to any differentiation processes and eruption. The only constraint is provided in regards to the stratigraphic sequence, which only limits the sequence of evolution to just prior to eruption. 5.1 Guachipelin Caldera silicic melt generation Stage 1 represents the inception of the Guachipelin magmatic system. This begins with dehydration melting of chemically distinct amphibole rich calc-alkaline sources producing the IM 2, IM 3, and IM 4 silicic melts (Figure 33). Also partial melting of an amphibole poor calc-alkaline source or a higher degree of partial melting relative to the other units generates the IM 1 silicic melt (Figure 33). The thermal energy needed to initiate this melting could be provided by advection from a hot-dry basaltic magma at the base of the crystalline rock or partially crystallized magma body (Tamura and Tatsumi, 2002) 170 .66.... .60...6> 06:06.. 6:... 6:60... 0:6 .665. .60...6> 06:66.. :66... 6.65 6:6:m 66.6 .6806... ..06... .6“. 626.... 66.6 06:00 6....:.. :66. :665 62.2.0. 66 6.:6Em6.. 60.E:.. E66656. 0.0..E>6 .6:0.>.0:. 2666020 .06... 6....95 0:6 .m6.0..0 06. 6...... .60:0E6.0 6....:.. ..66m. .6....6w. 66Em6E 0:...... 6... 60:00... 0. x.E 0.33 .6... 06.6650 626E .6...... 50. 6... .0 6:0...60..E00 6... 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Although there are only seven units defined, eight deposits are described due to the separate eruption of the Santa F e-high sub-group from the Santa Fe-low. Based on the data presented above, the following individual processes are related to each unit in the series of eruptions. The Guachipelin stratigraphic sequence starts with the eruption of: l) The Green Layer magma, volumetrically the smallest of the imits erupted (Figure 34). 2) The IM 2+EV 2 undergoes extensive mixing with the IM 1 erupting the modified Santa Fe-low magma (Figure 34). 3) An intermediate melt is extracted from the evolving IM 2+ EV 2 and mixes with the IM 3 forming the Salitral East hybrid magma (Figure 34). 4a,b) The EV 2 undergoes limited mixing with the IM 1 producing the Santa F e-high (Figure 34), a) this magma is subsequently erupted b) along with more of the Green Layer magma, which is a result of more extensive mixing between the EV 2 and IM 1 (Figure 34). These are two 173 ..:6>6 :0....3.6 .:666...6. 6.50:6 060.6 6.3:.6 06:00 0:6 .:0..6N.._6.6>.0 .6:0..06.. .:666...6. 62.0..6 060.6 6.9.6 062660 .m:.x.E .:666...6. 630.6 060.6 6.3300 0.8.... 60:63:66 62.036 :._6.....0630 6... E2. ..60..60 0:66.093 .630.>.0... ..066 .0 803.06 2.263036: 6... .0 E6.m6.0 E6EE3w .3. 6.33.“. » > 6....9.> b .3076... 6.:6w N .66.. :665 .. .D V Green Layer W9... 9.9.3. 9:66 .6 8 m 4 0.9.... . o N 6056 174 separate magma batches that are produced, the Green Layer deposit being the volumetrically subordinate unit. 5) The EV 2 mixes with the IM 4 forming the hybrid Pijije (Figure 34). 6) Immediately following this eruption the Liberia magma erupts (Figure 34). 7) Next, the IM 2+ EV 2 mixes with the IM 3 forming the hybrid Virginia (Figure 34). 8) The final eruption is the product of additional mixing between the IM 2+ EV 2 and IM 3 to produce the modified Buena Vista —low and -high; differences in these two magmas are a result of variability in the mixing proportions of the two initial melts (Figure 31). 175 VII. CONCLUSION The Guachipelin ignimbrites can be characterized as having seven chemically distinct, silicic ash-flow sheets. A review of several studies regarding silicic magma generation in subduction zone environments - absent of continental crust - suggest partial melting of an intermediate calc-alkaline source could produce dacitic-rhyolitic melts. The results of this study are consistent with these models. After the initial silicic melt was generated, differentiation processes are required to produce the chemical heterogeneity of the seven discrete ash-flows. Several possible methods of differentiation were tested in this study. The processes of fractional crystallization, partial melting of different intermediate sources, and mixing/ mingling were each evaluated and each played a role in the evolution of the Guachipelin magmatic system. It was concluded that extensive mixing and protracted magma residence are required to generate this series of co-genetic magmas. PolytOpic Vector Analysis (PVA) was used to evaluate mixing among four initial magma (IM) batches. The seven chemically distinct ash-flow sheets are the result of different proportions of mixing between these IM producing hybrid or modified magmas. Due to the extended residence of the IM 2 magma, it underwent limited crystal fractionation as it contributed melt, which would periodically mix with each of the other three initial melts as it evolved. In conclusion, the numerous explosive eruptions associated with the formation of the Guachipelin Caldera require a complex network of magma pathways to elicit the extensive magma mixing displayed in this volcanic suite. Contributions from each of the 176 four initial magmas occurred as discontinuous pulses that required protracted residence of several of these end-members. 177 APPENDIX A 178 Polytopic Vector Analysis The following explanation is taken directly from Tefend (2005): “Polytopic Vector Analysis (P VA) is explicitly designed to analyze samples that are mixtures; basically, each sample in a dataset is described in terms of some proportion of each end member generated by the program. Therefore, three parameters are needed to define a mixing system: 1) the number of end members, 2) the composition of each end member, and 3) the relative proportion of each end member in each sample within the dataset. Given knowledge of I ) and 2) the mixing proportions can be derived using many procedures. PVA is designed to estimate all three parameters from ambient data (e. g. chemical analyses of rock samples). The only assumptions are that every end member be present in low proportions in at least one sample and that the proportions of each end member within each sample sums to a constant (such as 1. 00). All mixing systems require plotting the data onto a geometric figure termed a simplex. A simplex may occur as a line with end members defined at the two ends (tw0 end member, like the plagioclase series), an equilateral triangle (3 end members), a symmetric tetrahedron (4 end members) or a higher dimensional equivalent. For instance a five and member system requires a four dimensional simplex. Unfortunately the term “simplex ” has been used as a label for the Simplex Method of Linear programming. T o avoid confusion, the PVA procedure was named Polytopic Vector Analysis. All simplexes are polytopes but not all polytopes are simplexes; only “equilateral ” polytopes are simplexes. PVA was developed by and for geologists, and has evolved over a period of about 40 years; the procedure is now used in many other fields. The initial impetus came fiom 179 John Imbrie who at the time was interested in grain size distributions and micropaleontological data sets (Imbrie, 1963; Imbrie and Kipp, 1971). Imbrie, and his graduate student Ed Klovan, coded up a version of “Qmode ” factor analysis where the data is placed in a covariance matrix that defines relationships between samples. This program was ultimately named “CABFAC ” (Klovan, 1968; Klovan and Imbrie, 1971) and is now widely used to analyze faunal assemblages associated with climate analysis. The next major development was made at the suggestion of Al Miesch, an igneous petrologist / geochemist at the USGS. Miesch and Klovan converted CABFAC into EXTENDED QMODEL and added the QMODEL procedure (Miesch, 1 976a; Miesch, I976b; Klovan and Miesch, 1976). Miesch wanted an analytical tool to test hypotheses. His concept was that petrologists had developed models of end member systems for a variety of igneous rock types and that a better way to evaluate sample data must exist in order to determine whether one or another model was feasible. Most petrologic data sets contain many more variables than the number of expected end members. If the variables (or analytes) were truly independent, then the data must be plotted using one reference axis for each analyte, in which case the data would plot as a multi-dimensional hypersphere. However, there are many correlations that exist between analytes such that fewer than k dimensions (where “k” is the number of variables) are necessary to enclose the data. Miesch and Klovan developed a superior way to determine the number of dimensions necessary for each variable: the now widely used "Coeflicients of Determination” table. Once the dimensionality of the data is known, then the number of end members required is simple: one more than the true dimensionality. So, if this analysis determined that the system required 5 end members, for instance, and theory 180 predicted three end members, then the theoretical system was incapable of defining the variability among samples. QMODEL permits the analyst to input compositions of theoretical end members to define a simplex, and if all sample data fits within the simplex, then the imposed end member system is feasible. If some samples fall outside the simplex, negative mixing proportions occur and either the model end members are incorrect, or there are problems with data accuracy. Finally, in I 982 the version that has evolved into the present version of P VA was developed in the context of a particular problem. The research group under Robert Ehrlich had developed a way to quantifi/ grain shape, and it soon became clear that grain shape frequency distributions were polymodal: the sand samples were mixtures of grains of various provenance or transport history. ‘ With the help of Klovan, PVA was developed; the principle developer was William Full (Full, et al., 1981, 1982; Ehrlich and Full, 198 7). Full ’s hyper-dimensional insight resulted in the creation of the DENEG procedure (Full, et al., 1981); when a simplex based on extreme samples in the dataset proved to be insuflicient or was mis-oriented the DENEG procedure allowed an iterative systematic enlargement and rotation of the simplex such that, at convergence, a simplex is defined where the compositions of each end member (located at the vertices) had non- negative components and all of the samples could contain non negative mixing proportions. At this stage the procedure was named EXTENDED QMODEL, which was then refined over the next 20 years, and the procedure was renamed PVA. The evolution in PVA continued with major improvements by Glenn Johnson, including the idea of the CD plot as well as the art and practice of P VA implementation with different data set (Johnson, 1997; Johnson, et al., 2000; Johnson, et al., 2002). 181 The VSPA CE Module PVA consists of 2 modules; the first module (VSPA CE) is a variant of Q mode factor analysis that decomposes the covariance matrix into eigenvectors. Eigenvectors represent a rotation of the reference axes that were previously defined by the analytes. As with the original axes, the eigenvectors are mutually orthogonal. The orientation of each eigenvector is controlled by the orientation of the cloud of multivariate variance. By design, the first eigenvector is oriented in the direction of highest variance; the second is oriented in the direction of the highest variance residual to the first, and so on. The amount of variance each eigenvector absorbs is measured by the eigenvalue associated with each eigenvector. Because eigenvectors represent progressively less variance, a common assumption is that at some level variance is so low that it mostly consists of random noise, so that if the higher numbered eigenvectors are disregarded, only noise rather than information is lost. This is the equivalent of projecting the data fiom the original number of dimensions defined by the number of analytes to a lower dimension defined by the reduced set of eigenvectors. A chronic problem has been to decide how many eigenvectors to discard. VSPA CE utilizes criteria first described by Klovan and Miesch (1976) and later, extended by Johnson et al. (2002). In general these criteria are based on the agreement, variable by variable, between the values in the original data and the values of each variable obtained by back calculation using progressively fewer retained eigenvectors. If for instance, all of the variables are well approximated by two eigenvectors, then all of the relationships between samples can be displayed on a two dimensional graph. As 182 discussed above, the number of end members is one higher than the number of necessary dimensions. Often it is unclear whether there are k or (k+1) dimensions; commonly both solutions are run. The difference between the two solutions ofien hangs on the “importance ” of the agreement between raw data and the back-calculated values for one or two variables. The PVA Module The second module is P VA proper. The task of the PVA module is to fit a simplex that encloses the data cloud once the number of end members is determined in the first module, VSPA CE. T wo criteria are needed to run PVA: 1) an initial guess for the initial simplex and 2) the DENEG procedure (Full et al.,1982). PVA is an iterative procedure; that is, it starts with an initial simplex and then enlarges and reorients it so as to leave no samples outside the final simplex such that all of the vertices (end member compositions) have elements in the negative orthant. There are several ways to define the location of the initial simplex; the preferred procedure is to choose the most mutually distant samples. The EXRA WC procedure attempts this by initializing on the k samples (where k is the number of end members), each having maximum varimax loadings on an eigenvector; next, a simplex defined by those points is constructed, and then tested, to determine whether any sample is located outside of the simplex (e. g. has negative mixing proportions). The Achilles heel of this option is its’ sensitivity to outliers that actually represent data analytical error or entry errors. However, proper use of information fi-om VSPA CE can largely mitigate this problem; hence, this is the default option in PVA. 183 It is a simple matter to determine which samples fall outside the polytope, as well as determine the composition of any vertex (the candidate end member); the DENEG procedure is an iterative procedure aimed at defining a simplex that encloses all samples and determines the compositions of the vertices. The procedure is designed to operate incrementally by moving any “side ” of the simplex outwards a given distance (the DNEG value) parallel to itself or until the DENEG distance contains no samples; at this point, the procedure signals convergence. Thus, each iteration has two parts: I) the movement of the simplex edges outwards, thus defining new vertices, and 2) changing any negative elements in the end member compositions to zero, thus rotating the simplex. Sometimes PVA does not converge, or it converges so slowly that the number of iterations is very large. If so, this can be ameliorated by either changing the DENEG value or accepting an iteration that has low negative values in either mixing proportions or end member compositions. Sometimes a lack of convergence reflects the fact that the data cloud is hyper-spherical and thus unmixing is not applicable. ” 184 APPENDIX B 185 Buena Vista-low The Buena Vista pumice fragments are light gray to tan in color, hypocrystalline with a degree of crystallinity ~21%. The matrix is dominated by a light and dark glass intermingled, with few microlites. Mineralogy: Most plagioclase are subhedral to euhedral, 0.05-2.875mm, albite twinning and oscillatory zoning are common. Amphibole are anhedral to euhedral, O.125-1.5mm, with some twinning and zircon inclusions. Fe-Ti oxides are anhedral to euhedral, 0.025- 0.75mm. Textures: Phenocrysts are found not only isolated, but in glomeroporphyritic clots of the smaller plagioclase, amphibole, and Fe-Ti oxides. A bi-modal distribution could be inferred based on the relative size difference between the plagioclase in the small clots and those that are isolated. Some plagioclase are anhedral and have sieve textures suggesting disequilibrium between mineral and melt. Amphibole have a brush-like texture along the rim, which could reflect disequilibrium between mineral and melt or be the result of eruptive fragmentation. ESTIMATED MODAL PERCENTAGE Primary: Plagioclase 1 5% Amphibole 3% F e-Ti oxides 3% Accessory: Zircon <<1 % 186 Buena Vista-high The Buena Vista pumice fragments are light gray to tan in color, hypocrystalline with a degree of crystallinity 8-21%. The matrix is dominated by a light glass with few microlites. Mineralogy: Most plagioclase are subhedral to euhedral, 0.05-2.875mm, albite twinning and oscillatory zoning are common. Amphibole are anhedral to euhedral, 0.75-2.25mm, with some twinning. Some amphibole have Fe-Ti oxide, biotite, zircon, or apatite inclusions. Fe-Ti oxides are anhedral to euhedral, 0.025-0.7mm, with zircon inclusions. Biotite are anhedral, 0.125-0.625mm. Quartz are anhedral, 0.05-2.5mm. Textures: ‘ Phenocrysts are found not only isolated, but in glomeroporphyritic clots of the smaller plagioclase, amphibole, and Fe-Ti oxides. A bi-modal distribution exists between a population of larger isolated crystals and the clots that occur as bands. Some plagioclase are anhedral and have sieve textures, overgrowths, or embayments suggesting disequilibrium between mineral and melt. Quartz are typically resorbed. Amphibole have a brush-like texture along the rim, which could reflect disequilibrium between mineral and melt or be the result of eruptive fragmentation. ESTIMATED MODAL PERCENTAGE Primary: Plagioclase 7-1 5% Amphibole <1-2% Biotite <1 (y . em «-20., Fe-Ti oxides 1-2% mc 1181011 Accessory: Zircon <<1% Apatite <<1% Biotite inclusion Fe-Ti oxide 187 Liberia The Liberia pumice fragments are light gray to tan in color, hypocrystalline with a degree of crystallinity l4-l6%. The matrix is dominated by a light glass with few microlites. Mineralogy: Most plagioclase are anhedral to subhedral, 0.05-3.625mm, albite twinning and oscillatory zoning are common. Amphibole are subhedral to euhedral, 0.075-1.5mm, with some twinning and Fe-Ti oxide inclusions. Fe-Ti oxides are anhedral, 0.025-1.25mm. Biotite are anhedral to euhedral, 0.025-1.875mm, some have Fe-Ti oxide inclusions. Quartz are anhedral, 0.125-4.5mm. Textures: Phenocrysts are typically found isolated, but some plagioclase are intergrown along with the Fe-Ti oxides. Some plagioclase have sieve textures and overgrowths suggesting disequilibrium between mineral and melt. Quartz are typically resorbed. Glass displays a distinct flow texture. ESTIMATED MODAL PERCENTAGE Primary: Plagioclase 7-8% Amphibole <1% Biotite 5-7% Quartz <1-2% Fe-Ti oxides <1% Accessory: Zircon <<1% 188 V'ggjnia The Virginia pumice fragments are light gray to tan in color, hypocrystalline with a degree of crystallinity ~4%. The matrix is dominated by a light glass. Mineralogy: Most plagioclase are anhedral to euhedral, 0.05-3.75mm, albite twinning and oscillatory zoning are common. Some plagioclase have amphibole or Fe-Ti oxide inclusions. Amphibole are anhedral to subhedral, 0.05-1.25mm, with some twinning. Fe-Ti oxides are anhedral, 0.025-O.375mm. Textures: Phenocrysts are found not only isolated, but in glomeroporphyritic clots of the smaller plagioclase, amphibole, and Fe-Ti oxides. Some plagioclase have sieve textures and embayments suggesting disequilibrium between mineral and melt. ESTIMATED MODAL PERCENTAGE Primary: Plagioclase 3-4% Amphibole <1% F e-Ti oxides 1% Accessory: Not observed Corroded plagioclase cores I n clu (led :I m philmlc 1.0mm 189 Salitral East The Salitral East pumice fragments are light gray to tan in color, hypocrystalline with a degree of crystallinity 8-10%. The matrix is dominated by a light glass. Mineralogy: Most plagioclase are anhedral to subhedral, 0.075-2.5mm, albite twinning and oscillatory zoning are common. Amphibole are subhedral to euhedral, 0.075-2.0mm, with some twinning and F e-Ti oxide, biotite, and apatite inclusions. Fe-Ti oxides are anhedral to subhedral, 0.025-0.75mm, with some zircon inclusions. Biotite are anhedral, 0.05- 0.875mm. Quartz are anhedral, 0.25-3.375mm. Textures: Phenocrysts are typically found isolated, but some plagioclase are intergrown along with the Fe-Ti oxides. Some plagioclase have embayments suggesting disequilibrium between mineral and melt. Quartz are typically resorbed. Glass displays a distinct flow texture. ESTINIATED MODAL PERCENTAGE Primary: Plagioclase 5% Amphibole 2-4% Biotite < 1% Quartz <1-1% Fe-Ti oxides 1% Accessory: Zircon << 1% Apatite <<1% ." . "79%.. 3*: @3334”. . J" “W '37; L. . a .. *' Amphibole 190 Pijije The Pijije pumice fragments are light gray to tan in color, hypocrystalline with a degree of crystallinity 10-50%. The matrix is dominated by a light and dark glass intermingled, with few microlites. Mineralogy: Most plagioclase are anhedral to euhedral, 0.05-5.0mm, albite twinning and oscillatory zoning are common. Amphibole are anhedral to euhedral, 0.175-1 .5m, with some twinning and Fe-Ti oxide inclusions. Fe-Ti oxides are anhedral to subhedral, 0.025- 0.75mm. Biotite are anhedral to euhedral, 0.05-2.5mm, some have Fe-Ti oxide inclusions. Quartz are anhedral, 0.075-3.75mm, with sparse amphibole inclusions. Textures: Phenocrysts are typically found isolated, but some plagioclase are intergrown along with the Fe-Ti oxides. Some plagioclase have sieve textures, overgrowths, or embayments suggesting disequilibrium between mineral and melt. Quartz are typically resorbed. Glass displays a distinct flow texture and microlites an intermediate trachytic texture. In samples that display two distinct glasses a bi-modal distribution of plagioclase and amphibole exists. ESTIMATED MODAL PERCENTAGE Primary: Plagioclase 6-40% Amphibole <1-10% Biotite 1-7% Quartz <1-10% Fe-Ti oxides <1% Accessory: Not observed 191 Santa F e-low The Santa Fe-low pumice fragments are light gray to tan in color, hypocrystalline with a degree of crystallinity ~8-l8%. The matrix is dominated by a light and dark glass intermingled, with few microlites. Mineralogy: Most plagioclase are anhedral to euhedral, 0.025-2.5mm, albite twinning and oscillatory zoning are common, with some Fe-Ti oxide inclusions. Amphibole are anhedral to subhedral, 0.125-2.5mm, with some twinning and Fe-Ti oxide inclusions. Fe-Ti oxides are anhedral, 0.025-0.5mm. Textures: Phenocrysts are not only found isolated, but in glomeroporphyritic clots of intergrown plagioclase, amphibole, and Fe-Ti oxides. Some plagioclase have sieve textures or embayments suggesting disequilibrium between mineral and melt. Amphibole have a brush-like texture along the rim and some have corroded cores, which could reflect disequilibrium between mineral and melt or be the result of eruptive fragmentation. ESTIMATED MODAL PERCENTAGE Primary: Plagioclase 6-15% Amphibole 1-2% Fe-Ti oxides 1% Accessory: Not observed Brush-like tutu re a Flirhibole » 192 Santa Fe-high The Santa Fe-high pumice fragments are light gray to tan in color, hypocrystalline with a degree of crystallinity 7-9%. The matrix is dominated by a light glass. Mineralogy: Most plagioclase are anhedral to subhedral, 0. 05- 3. 75mm, albite twinning and oscillatory zoning are common. Amphibole are anhedral to euhedral, 0. 15- 1.625mrn, with some twinning and Fe-Ti oxide inclusions. Fe-Ti oxides are anhedral to subhedral, 0.025- 0.45mm. Biotite are anhedral to euhedral, 0.125-2.125mm, some have Fe-Ti oxide inclusions. Quartz are anhedral, 0.25-5.0mm. Textures: Phenocrysts are typically found isolated, but some plagioclase are intergrown along with the Fe-Ti oxides. Quartz are typically resorbed. Glass displays a distinct flow texture and microlites an intermediate trachytic texture. ESTIMATED MODAL PERCENTAGE Primary: Plagioclase 3-7% Amphibole < 1% Biotite 1-2% Quartz 2-3% Fe-Ti oxides <1% Accessory: Not observed oscillatory 193 Green Layer The Green Layer pumice fi’agments are light gray to tan in color, hypocrystalline with a degree of crystallinity ~9-11%. The matrix is dominated by light glass, although some have a light and dark glass intermingled. Mineralogy: Most plagioclase are anhedral to euhedral, 0.25-4.9mm, albite twinning and oscillatory zoning are common. Amphibole are anhedral to euhedral, 0.25-2.75mm, with some twinning and Fe-Ti oxide inclusions. F e-Ti oxides are anhedral, 0.025-O.5mm. Textures: Phenocrysts are found not only isolated, but in glomeroporphyritic clots of the smaller plagioclase, amphibole, and Fe-Ti oxides. A bi-modal distribution of these minerals could be inferred based the size differences between the phenocrysts in the clots and those that are isolated. Some plagioclase have sieve textures or overgrowths suggesting disequilibrium between mineral and melt. Amphibole have a brush-like texture along the rim and/ or embayments, which could reflect disequilibrium between mineral and melt or be the result of eruptive fragmentation. ESTIMATED MODAL PERCENTAGE Primary: Plagioclase 7% Amphibole 2-4% Fe-Ti oxides 1% Accessory: Not observed A m phasing." ‘ 194 REFERENCES Acuna, A.B., Flores, R.C., Quiros, M.C., Salas, I.C., Cortés, J .C., Badilla, A.R., Ceder'io, ER, 2000. 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