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AAAAAA‘ 0 0 A am ‘ 1.910 This is to certify that the thesis entitled THE DEVELOPMENT OF EVAPORITE MINERALS DURING WEATHERING OF ANTARCTIC METEORITES presented by ANNA IZABELA LOSIAK has been accepted towards fulfillment of the requirements for the MS. degree in Geological Sciences Major Professor’s Signature r/Wfly2007 Date MSU is an Affirmative Action/Equal Opportunity Employer THE DEVELOPMENT OF EVAPORITE MINERALS DURING WEATHERING OF ANTARCTIC METEORITES By Anna Izabela Losiak A THESIS Submitted to Michigan State University in a partial fulfillment of the requirements for the degree of MASTERS OF SCIENCE Geological Sciences 2009 ABSTRACT THE DEVELOPMENT OF EVAPORITE MINERALS DURING WEATHERING OF ANTARCTIC METEORITES By Anna Izabela Losiak The purpose of this thesis is to advance the understanding of Antarctic weathering of meteorites (especially the development of evaporite minerals) at the scale of a single specimen and the scale of the entire population and continent. In the first paper, Scanning Electron Microscopy and Energy Dispersive Spectroscopy examination of eucrite EET790004 allowed identification of weathering phases present in the meteorite, as well as some inferences about the elemental redistribution within the specimen. Even though EET79004 is not indicated in the ANSMET database as evaporite-bearing, the outer most layer (3-4 mm) of the meteorite has its properties modified by weathering. Cracks are filled with Ca-sulfates; fiision crust vesicles are filled with large euhedral tabular Ca-S phases and small microcrystalline or amorphous K-S phases. Secondary REE carrying phases were not identified. The second paper discusses weathering of meteorites at the scale of the entire Antarctic Search for Meteorites program population. This paper updates, supplements and expands on the last Antarctic meteorite weathering census by Velbel (1988. Meteoritics 23, 151-159.) by analyzing the most recent version of the online ANSMET database that includes information about 15,263 meteorites. Meteorite compositional class and petrologic type have influence on formation of evaporites, while correlation with weathering classification is not conclusive. Number of evaporite-bearing meteorites vary also with geographic location of meteorite-bearing ice fields where the meteorites were found, and the year of collection. Dla Rodzicow, Ewy (i moich 50%) oraz mego ulubionego Ptysia ACKNOWLEDGMENTS I am very grateful to dr Michael Velbel for being the best advisor that I could wish to myself (or to anyone else). He taught me much more than just geology. I thank also: 0 Department of Geological Sciences for funding (Lucile Drake Pringle and Gordon H. Pringle Endowed Fellowship for 2007-2008 and Neal Endowed Scholarship for 2007- 2008) 0 Geological Society of America for the Graduate Student Research Grant. 0 Laura Schroeder and Ewa Danielewicz for collaborating on the initial SEM-EDS examination, 0 All participants of the Writing Group (especially Anne Axel) for helping me with editing initial manuscript. TABLE OF CONTENTS LIST OF TABLES ............................................................................................................. vi LIST OF FIGURES .......................................................................................................... vii Characterization of terrestrial weathering phases in EET79004 Antarctic eucrite ............. 7 Introduction ..................................................................................................................... 8 Materials & Methods ..................................................................................................... 10 Discussion ..................................................................................................................... 1 8 S-rich phases .............................................................................................................. 19 S redistribution .......................................................................................................... 20 Possible REE redistribution ....................................................................................... 23 Conclusions ................................................................................................................... 26 Appendix 1 .................................................................................................................... 28 REFERENCES .............................................................................................................. 46 Evaporite Formation during the Weathering of Antarctic Meteorites — a Weathering Census Analysis Based on the ANSMET Database ......................................................... 50 Methods ......................................................................................................................... 53 Results ........................................................................................................................... 55 Influence of meteorite composition (class) ............................................................... 55 Influence of petrologic type ....................................................................................... 59 Influence of weathering (rust) index ......................................................................... 61 Influence of geography .............................................................................................. 64 Influence of year of collection ................................................................................... 68 Discussion ..... . ............................................................................................................... 74 Influence of composition (class) ................................................................................ 74 Influence of petrologic type ....................................................................................... 80 Influence of weathering classification ....................................................................... 81 Influence of geography .............................................................................................. 82 Influence of collection year ....................................................................................... 87 Relative importance of parameters ............................................................................ 90 Conclusions ................................................................................................................... 92 Appendix 3 .................................................................................................................. 108 Appendix 4 .................................................................................................................. 1 10 Conclusions ..................................................................................................................... 121 LIST OF TABLES Table 1 Percent of evaporite-bearing meteorites, and average weight percent of chosen elements in relation to meteorite classification .............................................................................. 57 Table 2 Average porosity of meteorite groups based on published data for meteorite falls. ........ 57 Table 3 Evaporitic statistics for meteorite classes and weathering categories. ............................. 58 Table 4 Percent of evaporite-bearing meteorites with respect to petrologic types and weathering category of LL, L and H chondrites ................................................................................ 60 Table 5 Evaporitic statistics in respect to meteorite groups and weathering categories ................ 63 Table 6 Number of meteorites found along with number of meteorites with evaporite deposits in ice fields with 100 or more total cataloged meteorites. .................................................. 66 Table 7 Number of meteorites found and number of evaporite bearing meteorites as a function of a year of collection ............................... _ ............ - ..... 70 Table 8 Number of evaporite bearing L and H chondrites as a function of year and field of collection ........................................................................................................................... 1 Table 9 List of the AN SMET laboratory staff through time. ........................................................ 73 Table 10 Percent of evaporite-bearing meteorites as a function of location within the LEW ice field for H and L chondrites ............................................................................................ 86 Table 11 Relation of weather in a given year to under— or over-abundance of evaporites. ........... 90 Table 12 Simplified meteorite classification. .............................................................................. 109 Images in this thesis are presented in color. vi LIST OF FIGURES Figure 1 EET79004 lab image .......................................................................................... 11 Figure 2 Clasts and matrix fragments from the interior sample 64 of EET7 9004 ............ 14 Figure 3 The outermost fragment of the exterior sample 59 of EET79004 ...................... 17 Figure 4 Large vesicle present in the fusion crust (sample 59). ...................................... 18 Figure 5 Map of meteorite fields on Antarctica .................................................................. 1 Figure 6 Percent of meteorites with evaporites as a function of compositional group. 76 Figure 7 Percent of meteorites with evaporites in respect to average chemical composition of the meteorite group. ................................................................................. 78 Figure 8 Average porosity and percent of evaporite-bearing meteorites .......................... 80 Figure 9 Location of sub-ice fields within the Lewis Cliff location (AMLAMP web page). ................................................................................................................................. 85 Figure 10 Percent of meteorite with evaporites for total population collected in given year ...................................................................................................................................... 1 vii INTRODUCTION The purpose of this thesis is to advance the understanding of Antarctic weathering of meteorites (especially the development of evaporite minerals). Most studies focus only on the scale of a single specimen, and do not take into account the characteristics of the environment where it was found. In fact in most cases the influence of environment where the meteorite was weathering for hundreds of thousands of years (N ishiizumi et a1. 1989, Nishiizumi et a1. 2000) is totally ignored, and not even mentioned in the analysis. This thesis is an attempt to bridge between those two scales. Understanding terrestrial weathering of Antarctic meteorites is important for two main reasons. First, weathering processes can modify meteorite characteristics (e.g., trace-element abundances) and thereby interfere with the retrieval of information about pre-terrestrial solar system processes (e.g., Gooding 1981, Bland et a1. 2006). This problem can be especially significant when dealing with rare types of meteorites, for which populations Antarctic samples may constitute a major fraction. A second reason to study Antarctic meteorites is because such study can provide information about the environment processes of Antarctica (e.g., Bland et a1. 2000, Harvey 2003). Many studies have applied knowledge about meteorites to obtain new information about: ice movement (e.g., Benoit and Sears 1999, Folco et. a1 2006, Welten et al. 2008a), climate changes (Delisle 1993), liquid water availability within the ice (Harvey and Score 1991, Krahenbuhl and Langenauer 1994), weathering rates (Bland 2006) and reconstructing historical volcanic activity (Curzio 2008). Meteorite classification is based on chemical and textural properties (details on meteorite classification are given after Hutchinson (2004)). Meteorites are divided into three basic categories: irons, stony irons and stony meteorites. A somewhat simplified (especially for non-stony meteorites) classification is used in Table 1 and described in Appendix 3. Only stony meteorites will be discussed in detail in this paper. There are two distinct kinds of stony meteorites: chondrites and achondrites. Chondrites are much more abundant (Hutchinson 2004). They consist of primitive material that condensed from a solar nebula (later have been accreted into small asteroids) but have not undergone a significant amount of reprocessing since then. There are three main compositional classes of chondrites: enstatite chondrites, ordinary chondrites and carbonaceous chondrites. Some of the groups are further divided into multiple classes, for example; the ordinary chondrite class includes H, L and LL groups. All chondrites have undergone some modification that resulted in metamorphism (up to melting of primitive material) and/or aqueous alteration. The classification of petrologic types of meteorites is used to describe both; how the meteorite was modified and the extent of the modification. Petrologic type 3 means minimal modification by either of the processes, type 6 indicates a meteorite that underwent significant metamorphic reprocessing and type 1 means that the meteorite was strongly affected by aqueous alteration. Olivines and pyroxenes present in meteorites of low metamorphic grades have variable abundances of Mg and Fe, while the same minerals in meteorites of petrologic type 6 have more uniform (equilibrated) composition of those minerals. Achondrites are meteorites that do not include chondrules, and their chemical compositions suggest significant reprocessing of primary material. Achondrites originate from asteroids and are often a result of volcanic reprocessing and differentiation of primary material. Both types of stony meteorites are often brecciated. When a meteorite lands on the surface of the Earth it starts to weather. Weathering processes and rates depend mostly on the environment in which meteorite has landed (e.g., Bland et al. 1998, Lee and Bland 2004, Bland 2006) but also on the composition of the meteorite itself (Velbel 1988). Different classes and groups of stony meteorites have very different chemical and textural properties that result in different susceptibility to weathering (e.g., Bland et al. 2000) and thus evaporite formation. For example, Velbel (1988) found that formation of evaporites on C chondrites is much more common than on any other meteorite group. However, the small number of available meteorites prevented Velbel from making more detailed comparisons among different groups (with the exception of LL, L and H and E chondrites). Velbel (1988) also proposed that within each compositional group, evaporite distribution varies with petrologic type. Weathering rates in Antarctica are relatively low when compared to other terrestrial environments (Campbell and Claridge 1987). As a result, terrestrial ages of Antarctic meteorites are on average much higher than non-Antarctic (Nishiizumi et al. 1989, Welten et al. 2008b) because they are removed slower from the environment. However, Antarctic weathering can be rapid; Jull et al. (1988) found that hydrous magnesium carbonates can form in less than 40 years. Additionally, studies of meteorites found enclosed in the ice prove that chemical changes in meteorites can be very rapid and occur in a scale of few years or even months (Harvey and Score 1991, Krahenbuhl and Langenauer 1994). Weathering changes the chemical, isotopic and textural properties of meteorites (e. g., Bland et al. 2006). One of the first effects of weathering is the oxidation of iron and formation of Fe-oxides and oxihydroxides that give a meteorite a rusty- reddish color (e.g., Gooding 1981, 1986). Another result of weathering is dissolution of primary minerals such as olivine and pyroxene, and formation of clays and other pyllosilicates (e.g., Gooding 1986) as well as evaporites (e.g., Velbel et al. 1991, Gounelle and Zolensky 2001). The bulk chemical composition of weathered meteorites can also change. Major elements are mobilized (V elbel et a1. 1991, Lee and Bland 2004, Al-Kathiri et al. 2005), rare earth elements are redistributed (e.g. Mittlefehldt and Lindstrom 1991, Crozaz et a1. 2003) Some meteorites (e.g., CM) have undergone quite extensive aqueous alteration before arriving at Earth what resulted in changes of their chemical characteristics e.g., in the Mg/Fe ratio increases in the matrix (e.g., McSween 1979, Goswami and Macdougall 1983, Browning et al. 1996, Brearley 2006). Products of pre-terrestrial aqueous alteration are ofien very similar to those resulting from weathering, and distinguishing between those two can be problematic (e.g., Gounelle and Zolensky 2001 ). Antarctic meteorite weathering classification is based on a relative “rustiness” visible to the unaided eye (for further details refer to a recent issue of Antarctic Meteorite Newsletter). There are five weathering categories ranging from A (meaning minor) to C (for severe rustiness) (Table 1). Additionally, the weathering classification includes the letter “e” if there were any evaporites when meteorite was found (V elbel 1988). The analysis in this paper is based mostly on the presence of this indicator. Velbel ( 1988) concluded that evaporites preferentially form in early stages of weathering (with small amount of rust visible), although the number of available specimens was low and differences between percentages of meteorites with evaporites within different groups was not large. Weathering depends strongly on characteristics of the environment (e. g., Gooding 1986, Bland 2006). The rate of weathering in the Antarctic environment is limited by the temperature and (related to this) low liquid water availability. Precipitation has much less impact, since most precipitation falls as snow, not liquid water (Campbell and Claridge, 1987). Temperature and precipitation vary somewhat among different meteorite-bearing fields (Comiso 2000, Chapman and Walsh 2007), which can potentially cause differences in weathering. Additionally, it is possible that microclimatic conditions vary among locations (Harvey 2003). Losiak and Velbel (2009) suggested a relationship between geographic location and evaporite formation on Antarctic meteorites. Average monthly temperature over Antarctica varies by more than 15°C (Comiso 2000, Chapman and Walsh 2007). Some years are unusually cold, other are much warmer. For example, July (winter) temperature in 1979, 1985, 1987, 1993 and 1997 were lower than average surface temperatures, while 1980, 1981, 1982, 1984, 1991 and 1995 and 1996 were unusually warm. Summer temperatures also vary: in 1979, 1981, 1995 and 1998 it was unusually cold, whereas summers in 1986, 1988, 1990 and 1991 were warm. These climate deviations can potentially cause variation in the weathering rate and thus evaporite formation on Antarctic meteorites. The thesis consists of two parts that address the same issue of evaporite-mineral development at two different scales; the scale of a single specimen and the scale of entire population and continent. The first paper discusses weathering in the Antarctic environment at the scale of a single specimen. The Scanning Electron Microscope and Energy Dispersive X—ray Microanalysis examination of eucrite EET790004 allowed identification of weathering phases present in the meteorite, as well as some inferences about the elemental redistribution within the specimen. The second paper discusses weathering of meteorites at the scale of the entire Antarctic Search for Meteorites program population. This paper updates, supplements and expands on the last Antarctic meteorite weathering census by Velbel (1988) by analyzing the most recent version of the online Antarctic meteorite classification database that includes information about 15,263 meteorites. It discusses influences of meteorite compositional class, petrologic type, weathering classification, geographic location of meteorite-bearing ice fields where the meteorites were found, and the year of collection, on the occurrence of evaporite formation on a population of Antarctic meteorites. CHARACTERIZATION OF TERRESTRIAL WEATHERING PHASES IN EET79004 ANTARCTIC EUCRITE Abstract The purposes of this paper are to identify elemental redistribution and the distribution of possible weathering features in interior and exterior thin-sections from the same meteorite EET79004. Optical petrography, BSEM and EDS methods were used. EET79004, although not indicated as evaporite-bearing in the Antarctic Meteorites Database includes evaporite minerals (mostly Ca—sulfates) filling cracks in the outermost 3-4 mm. Vesicles are filled with large euhedral tabular Ca-S phases and small microcrystalline or amorphous K-S phases. Eucrite EET79004 is characterized by an unusual REE redistribution probably related to terrestrial weathering (Mittlefehldt and and Lindstrom , 1991, Geochimica et Cosmochimica Acta 55, 77-87) and an attempt was made to evaluate whether, and to what extent the visible weathering features are related to the previously reported REE redistribution created probably during weathering of this meteorite and identify secondary host phases of REE in these materials. Although some P-Ca phases with high Z-contrast have been found used techniques and small size of phases, it was not possible to determine if they are the REE host phases. Introduction While weathering can modify meteorite characteristics (e.g., distributions of elements, minerals present in the sample, trace-element abundances and isotope characteristics) and thereby interfere with the retrieval of information about pre-terrestrial solar system processes (e.g., Gooding 1981a,b, Bland et al. 2006), it can also facilitate the study of past terrestrial environments. Bland (2006) has listed many factors which make meteorites very useful in research on terrestrial weathering rates. Among other reasons, meteorites constitute a group of material with very similar, well known composition, that are distributed uniformly on the surface of the Earth, and from which terrestrial ages can be determined. Meteorite EET79004, studied in this paper, is a eucrite. Eucrites are the most abundant group of achondrite meteorites (e.g., Hutchison 2004). Eucrites, along with howardites and diogenites, are part of HED meteorite group. HED meteorites are thought to come from asteroid 4 Vesta (e.g., Drake 2001, Sykes and Vilas 2001). EET79004 is a polyrnict eucrite; which means that it has less than 10% orthopyroxene and includes clasts of rrrineralogically different eucrites (including basaltic and cumulate eucrites) (Hutchison 2004). Eucrites consist mostly of basaltic clasts (which can have ophitic textures, some of them with preferentially oriented plagioclases) and a matrix of small fragments of augite and calcic feldspar (Hutchison 2004). Some eucrites (mostly basaltic) have undergone different degrees of thermal metamorphism. Almost all eucrites are brecciated to some degree (Hutchison 2004). Eucrites have been chosen for this study of low temperature terrestrial weathering because HEDs are anhydrous igneous rocks; consequently, any aqueous alteration features can be inferred to have formed under reasonably well-known Antarctic conditions. The second reason is that HEDs are igneous rocks more similar to an average igneous rock weathered under cold and water-poor conditions than any other abundant class of meteorites (Takeda 1997, Hutchison 2004). The similarity between eucrites and terrestrial basalts can allow comparison and extension of results from different localities. Meteorites found in Antarctica are very attractive subjects for weathering studies because they have been extensively studied before and literature about their chemical composition, dating and mineralogy is available (e.g., Mittlefehldt and Lindstrom 1991). Meteorite EET79004 was selected for this study because it was shown by Mittlefehldt and Lindstrom (1991) that interior and exterior parts of this meteorite have different rare earth elements (REE) abundances. They showed in their Figure 4 that, relative to the corresponding interior sample, an exterior sample of EETA79004 is enriched (by less than a factor of two) in La, Sm, & Tb (LREE); depleted (by less than a factor of two) in Ce; and has nearly identical Eu, Yb, & Lu abundances (the latter, HREE). Mittlefehldt and Lindstrom (1991) concluded that this pattern results from weathering processes This conclusion was subsequently supported by the finding that LREE enrichment, a negative Ce anomaly and a very similar REE redistribution pattern is typical of weathering of terrestrial basalts under oxidizing conditions (Patino et al. 2003). Although studies of REE mobilization in terrestrially weathered materials are abundant, research on REE mobility in extraterrestrial materials is rare (Shimizu et al. 1983, Mittlefehldt and Lindstrom 1991, Crozaz et al. 2003). Secondary host phases of REE have been moderately well characterized in weathered terrestrial rocks (e. g., Banfield and Eggleton 1989, Cotton et al. 1995, Taunton et al. 2000), but not yet for meteorites. The purposes of this paper are to (1) identify the elemental redistribution and possible weathering features in interior and exterior thin-sections from the same meteorite, using optical petrography, BSEM and EDS; (2) investigate the distribution of identified weathering features and how they differ between the interior and exterior thin- sections, (3) evaluate whether, and to what extent the visible weathering features are related to the previously reported REE redistribution created probably during weathering of this meteorite, and if possible (4) identify secondary host phases of REE in these materials. Materials & Methods EET79004 was collected by the Antarctic Search for Meteorites program (ANSMET) during field season 1979 on the Elephant Moraine meteorite-bearing ice field. When it was collected it weighed 390.3 g and its size was approximately 11x6.5x4 cm (Figure 1). In ANSMET the database (www.curatorjscnasaggov/antmet) as well as in Delaney et a1 (1982) this meteorite was classified as a polymict eucrite. However Mittlefehldt and Lindstrom (1991) suggested that it is a monomict eucrite. Characterization of some aspects of this meteorite was previously provided in The Antarctic Meteorite Newsletter, Delaney et al. (1984), and Mittlefehldt and Lindstrom (1991). 10 ‘1’" EETA79004 Figure l EET79004 lab image (www.curatoriscnasa.gov/antmet), after partial separation of subsarnples. Back surface visible on the right side is a fusion crust. EETA7900, when collected, was almost entirely covered with fusion crust (Antarctic Meteorite Newsletter 3,3). The matrix of this meteorite is gray in color and includes multiple clasts of darker color material (although light colored clasts are also present) up to 2 cm in diameter (Antarctic Meteorite Newsletter 3,3). Some rusting was visible, and because of that the meteorite has been assigned to weathering category B (e.g., Velbel 1988). No evaporites were found on its surface during recovery or classification. EET79004 consists of pyroxenes (WozEn45F353 to Wo4oEn36Fsz4) and feldspars (OrlAb6An93 to OrlAb14An35) in a fine-grained matrix of pyroxenes and plagioclases similar in composition to those in clasts (Antarctic Meteorite Newsletter 3,3). Most clasts are angular, although some may have less perfectly defined outlines that suggest that they underwent reheating (Antarctic Meteorite Newsletter 3,3). 11 For the purpose of this study two uncovered polished thin sections of EET79004 were analyzed. Sample 59 comes from the weathered rim of the meteorite and includes a portion of the fusion crust. Sample 64 comes from a more interior part of the meteorite than does sample 59 (at least 1 cm below the fusion crust). Methods used in this study are similar to those previously successfully used to identify products of weathering in terrestrial and extraterrestrial materials (e. g., Banfield and Eggleton 1989, Cotton et al. 1995, Taunton et al. 2000, Wade 2002). Samples have been characterized using instruments available at Michigan State University’s Center for Advanced Microscopy. Scanning electron microscope (SEM) (J EOL 6400V Japan Electron Optics Laboratories with a LaB6 emitter (Noran EDS)) was used mostly in a backseattered electron mode (B SE) to image contrasts in an average atomic number within the sample. Additionally, elemental maps using Energy Dispersive X-ray Microanalysis (EDS) (Noran EDS) were produced. These methods allowed obtaining information not only about the composition but also about the spatial relations between different phases and the distribution of elements. No method allowing quantitative characterization of phases was available at this stage of the study. No available method allowed structure characterization; thus no rrrinerals could be identified (no minerals names will be used in reference to phases identified in this study). Thin sections are carbon-coated; because of this the distinguishing of carbonate phases using EDS is not possible (the signal from in the coating is superimposed on the signal from the carbonate minerals’ C02 group). 12 Results The comparison between the samples from the interior and exterior of EET79004 reveals differences in the distribution of elements and weathering features. The interior sample 64 as well as the interior part (below ~4mm of firsion crust) of sample 59 look relatively fresh (Figure 2, Appendix 1 Figure 14, Appendix 1 Figure 15, Appendix 1 Figure 16, Appendix 1 Figure 17). Based on the elemental maps samples were determined to consist of pyroxene and plagioclase with some addition of other phases including large concentrations of Ti-Fe, Cr-Mn and Si that are rather typical for eucrites (Hutchinson 2004). The meteorite consists of large clasts (up to more than 1 mm in diameter) that can either be one grain (pyroxene or plagioclase) (Figure 2a,b,c,d, Appendix 1 Figure 14, Appendix 1 Figure 15, Appendix 1 Figure 16, Appendix 1 Figure 17) or a mixture of different phases — some of them have distinctive ophitic texture (Figure 2a, Appendix 1 Figure 14). Some of the pyroxenes show some compositional zoning with more Mg rich cores, and more Fe rich rims (Figure 2c, Appendix 1 Figure 16). Other pyroxenes have cxsolution larnellae with different Ca/Fe abundance (Appendix 1 Figure 1, Appendix 1 Figure 8, Appendix 1 Figure 10, Appendix 1 Figure 11, Appendix 1 Figure 17). Plagioclase composition is much more uniform and no zoning or exsolution features were observed. Clasts are usually surrounded by cracks that are empty in the sample 64 and interior part of sample 59. The matrix consists of much smaller phases (usually <100jrm in diameter) of the same type of grains as grains (Figure 2d, Appendix 1 Figure 17). 13 Figure 2 Clasts and matrix fragments from the interior sample 64 of EET79004, a) Clasts with ophitic texture (tabular dark gray plagioclase crystals in pyroxene), b) Clast without opitic texture, c) Clasts consisting of single pyroxene grain with zoning visible (lighter outermost part is more Fe rich), d) matrix — dark gray are plagioclases, light gray pyroxenes and very light are various Ti-Fe and Cr-Mn-F e oxides. The most distinctive difference between interior and exterior samples is the presence of S-rich veins in the outer most part of the 59 sample up to a depth of about 3-4 mm (Appendix 1 Figure 9, Appendix 1 Figure 11, Appendix 1 Figure 12). Interior sample 64, and the interior part of 59, do not show any indication of similar features (Appendix 1 Figure 12, Appendix 1 Figure 17). The network of veins highlights the brecciated character of the meteorite. Veins are present also inside the clasts, but these are much thinner and less abundant. Most clasts have particularly thick veins around the 14 clasts and large mineral gains. The boundary between the interval where veins are present and absent is parallel to the preserved firsion crust (Appendix 1 Figure 12). The transition from the interval with and without S-rich veins is quite abrupt (Appendix 1 Figure 12). It is linear, with only a few irregularities, and it is slightly thicker in proximity to a relatively large vein (Appendix 1 Figure 12). Not all voids visible in the BSE images are filled with the material. Some fragnents of material filling the voids look cracked or contracted (Appendix 1 Figure 1, Appendix 1 Figure 6). EDS maps reveal that the material filling the veins consists mostly of S and Ca (Appendix 1 Figure 1, Appendix 1 Figure 4, Appendix 1 Figure 6, Appendix 1 Figure 9, Appendix 1 Figure 10, Appendix 1 Figure 11, Appendix 1 Figure 12); if some other element is present, it is below the detection limits. Based on the available data, all veins consist of similar material (however it is possible that using more detailed methods, more varieties of this material would be revealed). No Mg—S-rich phases were found in this meteorite, either as void- or vein-fillings. P-rich phases have been found in two places, both within the same gain of calcium plagioclase (one of those occurrences is shown on Appendix 1 Figure 3). These phases have a light color in the BSE images indicating that they include elements with high atorrric numbers. However, the admixtures are not large enough to be identified in the EDS maps (except possibly for increased Ca). P-rich phases occur as elongated fillings of small cracks within the plagioclase. One of the occurrences looks as if it was divided by a more recent and larger crack (Appendix 1 Figure 18). Phases consisting of Cr, Mn, Fe, and A1 are also present in other veins that crosscut pyroxenes (Appendix 1 Figure 3, Appendix 1 Figure 5, Appendix 1 Figure 8). 15 The phases are very light in color on BSE images showing that they include high atomic numbered elements. In a few cases those phases are crosscut by the S-rich phase filled veins. Alteration features (irregular pits on the cracks walls) of primary minerals such as plagioclase and pyroxene have been found to be sporadic. When they are found they are present only in the outer most part of sample 59 — only in the layer including S-rich veins. Alteration phases are more common in plagioclases and have the form of rather irregular voids visible on the surface of the veins walls (Appendix 1 Figure 4). There are some phases located inside the vesicles of fusion crust (Figure 3, Appendix 1 Figure 2, Appendix 1 Figure 7, Appendix 1 Figure 10, Appendix 1 Figure 13). Not all vesicles are filled with the material, although it is possible that some phases were removed during sample preparation. There are two types of material partially filling vesicles. The first type is large (up to ~40jrm in length), euhedral, tabular crystals (Figure 3, Appendix 1 Figure 9, Appendix 1 Figure 10, Appendix 1 Figure 13). The EDS maps show that they consist of S and Ca. The second type of vesicle-filling is less common and consists of much smaller phases (up to few pm in diameter) (Appendix 1 Figure 7). Some of the material is ganular, other occurrences seem to be amorphous (at least at the scale at which observations were made). Grains vary in shape from slightly elongated to almost spherical. EDS maps show that they consist of Al, S, K and possibly Si. 16 Figure 3 The outermost fragment of the exterior sample 59 of EET79004 with fusion crust. Some of the vesicles present in the fusion crust are filled with weathering phases, b shows close up of a fragnent marked by white rectangle. A pyroxene with cxsolution is visible in the lower left comer. A small nickel rich phase is visible on the right part of the wall of the right large vesicle (a close up shown in Figure 4). Two occurrences of small Ni-rich phases have been identified on the walls of large vesicles (Figure 4, Appendix 1 Figure 2, Appendix 1 Figure 13). They are euhedral, elongated crystals, slightly less than 10-20um in size. Both identified examples have been found in vesicles filled with large euhedral crystals of Ca—S-rich phase. Based on EDS maps the Ni-rich phase consists only of Ni, however it cannot be excluded that it also includes trace amounts of other elements, especially elements that are more abundant in immediately adjacent phases. 17 Figure 4 Large vesicle present in the fusion crust (sample 59). White phase consisting of Ni is visible on the wall of the large vesicle. The large tabular crystals inside the vesicles consist of Ca and S. Smaller vesicles are filled out with a phase consisting of K and S. Tabular crystals are crosscutting the vesicle walls, what shows that they are younger than fusion crust. Discussion EET79004 is devoid of visible evaporites (as listed in the ANSMET database). However the detailed examination of external sample 59 revealed abundant evaporite (sulfate) material present within and just below the fusion crust (to the depth of 3-4mm) (e.g., Appendix 1 Figure 9, Appendix 1 Figure 12). This shows that evaporites are more abundant than just based on indications present in the ANSMET database. The statement that ~5% meteorites collected in Antarctica includes evaporites (V elbel 1988, Losiak and Velbel 2009) should be modified to: at least 5% of meteorites found in Antarctica have evaporites. 18 S-rich phases The outermost part of the EET79004 contains abundant S-rich phases of a few different types. Vesicles in the EET79004 contain two types of minerals: Ca and K sulfates (Appendix 1 Figure 13 and Appendix 1 Figure 7 respectively). Ca sulfates partially filling some of the vesicles occurs as large tabular crystals. They probably consist of gypsum; however they can also be any other Ca-S mineral like anhydrite or bassanite. Gypsum has been previously reported on Antarctic meteorites (e.g., Velbel 1988, Wentworth and Gooding 1991) as well as on terrestrial rocks of Transantarctic Mountains (Campbell and Claridge 1987). Because of this gypsum is inferred. K-sulfate does not have a distinct euhedral shape, unlike Ca-sulfate. K-sulfates have been reported previously by Gooding (1981) as a marnillary material filling the fusion crust voids of ALHA77296 (HS chondrite); however the mineral itself has not been identified. The phase found on the EET79004 (Appendix 1 Figure 7) and the one found by Gooding (1981) can be the same type of mineral; both of them consist mostly of K and S, they are located in a very similar arrangement (vesicle fillings of Antarctic meteorites) and they look similar (compare Figure 11.1 in Gooding (1981) and Appendix 1 Figure 7). Abundant S-rich phases partially fill veins in the outermost 3-4 mm. Sulfate veins in carbonaceous chondrites were sometimes attributed to an extraterrestrial origin (e.g., Zolensly and McSween 1988). However, Gounelle and Zolensky (2001) have argued that most vein sulfates in C-chondrites result from weathering in terrestrial conditions. Multiple sulfate minerals of a given cation ofien differ only by the hydration state, and a large diversity in the hydration states of the sulfates found in the veins was identified (e.g., DuFresne and Anders 1962, Richardson 1978). Sulfates can change their 19 hydration state in response to change in atmospheric conditions especially relative humidity (Klimchouk 2000) due to changes of, for example, conditions on the ice, or between on-ice and in-laboratory conditions. This can result in the expansion or contraction of minerals by hydration or dehydration respectively (Klimchouk 2000). Cracks and voids observed in the Ca-sulfate filling of the veins from the exterior part of sample 59 (Appendix 1 Figure 9, Appendix 1 Figure 12) may similarly be related to changes in hydration state. S redistribution Sulfur is one of the elements that is the easiest to redistribute during weathering. In most Earth surface environments sulfates are leached from weathering profiles (e.g. Velbel and Gooding 1991). Only if water abundance in the environment is very low, sulfate minerals can be precipitated and preserved in the soil or saprolite (Campbell and Claridge 1987). Various sulfates, mostly Ca and Mg, are found in soils of hot and cold deserts (e.g., Gooding 1981a, Barrat et a1. 2003, Lee and Bland 2004). S is more mobile during weathering in hot desert conditions and large fiactions of this elements initially present in the meteorite are leached out by episodic wetting (Ruzicka 1995, Lee and Bland 2004). Sulfate phases are commonly found in Antarctic soils as discrete layers in the top part of soil profiles (Campbell and Claridge 1987, Wentworth et al. 2005). Sulfur is present in low concentrations in all weathering products and at least in part comes from troilite weathering (Marvin and Motylewski 1980, Gibson and Andrawes 1980, Lee and Bland 2004). Some sulfur present in evaporites can originate from atmospheric aerosols (Campbell and Claridge 1987). Sulfate minerals (Fe-sulfates and K-Fe-sulfates, Mg- sulfates: epsomite, starkeyite, as well as Ca-sulfates: gypsum) are found on Antarctic 20 meteorites (V elbel 1988). Although the phase present in the veins of EET79004 cannot be identified without data about its crystal structure, it is probable that the Ca—S-rich vein filling is gypsum. The sources of cations and anions present in the sulfates are not clear. It was shown that the Mg found in some Mg—carbonate evaporites comes from weathering of olivines present in the meteorite (V elbel et al. 1991). The source of Ca has not been revealed in the literature yet, although it can be inferred by the analogy with Mg that Ca comes from weathering of parent minerals in the meteorite, in this case calcium plagioclase or high-Ca-pyroxene). The source of K cations is less clear. In eucrites K is commonly present in very small amounts (less than 0.1% Hutchison 2004). The main K host mineral is orthoclase. In EET79004 1% of all feldspars is orthoclase (Antarctic Meteorite Newsletter, 1980). The K abundance is larger in exterior sample (930 ppm) than in interior (280 ppm) sample of EET79004 (Mittlefehldt and Lindstrom 1991, table 3). However, it is not clear if this variability shows redistribution of K during weathering or just heterogeneity of sample. The source of anions present in the Mg-carbonates found on the ordinary chondrites is terrestrial (Jull et al. 1988, Velbel et al. 1991). S sources have not been identified. It is possible that part of the S comes from weathering of troilite. Troilite is a common primary S mineral in eucrites (e.g., Hutchinson 2004). Some phases consisting mostly of Fe and S (most likely troilite) have been identified in the sample 64 and in the interior part of sample 59, however they are absent in the layer of sample 59 where Ca-S- rich veins are present (Appendix 1 Figure 9, Appendix 1 Figure 12, Appendix 1 Figure 17). Some S can also come from Antarctic environment Kelly and Zumberge (1961) 21 showed that the most weathered samples of quartz diorite that they studied have slightly elevated Na, Cl and sulfate values. They have attributed this to contamination by the sea spray. The bulk of the aerosolic material collected during 1974-1975 summers at the South Pole was sulfate and was probably of marine origin (Campbell and Claridge 1987). No data about the bulk S abundance in the interior and exterior sample is available so it is not possible to compare the distribution of this element between those two locations. However, based on EDS maps it seems that S is enriched in the outermost part of the sample. If this is true, it would require an additional source of S because the troilite in the interior part of sample seems to be un-weathered (Appendix 1 Figure 12, Appendix 1 Figure 16). S can come from either redistribution from inner parts of meteorite itself, or from fluids circulating in and on the ice (possibly contaminated by sea spray). Velbel (1988) observed that Mg—carbonates develop on achondrites, while sulfates occur primarily on carbonaceous and unequilibrated ordinary chondrites. However, this statement was based on a small number of available published nrineralogical determinations, so the fact that a sulfate is present on eucrite EET79004, and no Mg-carbonates have been identified, is not anomalous. Study of the entire population of Antarctic meteorites (Losiak and Velbel 2009, Losiak, this volume) revealed that the distribution of evaporites on Antarctic meteorites depends not only on the composition of meteorite (as stated previously by Velbel 1988), but can also be correlated with the geogaphical location of meteorite recovery as well as the year of meteorite collection. If the amounts of evaporites present on the surface of meteorites changes because of these variables, it may also be that the type of evaporite present also varies depending on environmental properties (not only meteorite composition). 22 Campbell and Claridge (1987) have showed that the type of evaporites found in the soils and in proximity of melt pounds in Antarctica differs depending on location where they were found. However the hypothesis linking type of evaporite material present to the location cannot be tested in this study. Possible REE redistribution EET79004 was chosen for this study because Mittlefehldt and Lindstrom (1991) demonstrated that this meteorite is characterized by abnormal (non-petrologic) patterns of REE distribution, which they interpreted to result from weathering processes. Mobilization of REE can be used in terrestrial rocks as an indicator of very early stages of weathering: REE abundances in some regoliths considerably increase in early stage of chemical alteration and decrease afterwards (e.g., Cotton et. al. 1995, Patino et al. 2003). Much research suggests that distribution of REE is related to phosphate rrrinerals (e. g., Cotton et. al. 1995). Taunton et al. (2000) provide a possible explanation of this process. They suggest that initial weathering of ganodiorite removes both allanite (which in this rock is the main, primary host of REE), and apatite. Subsequently secondary REE- bearing phosphate minerals such as rhabdophane and florencite are precipitated. The Ce and other light REE are fiactionated because Ce oxidizes to 4+ and becomes immobile, while other REE remain soluble. Development of the negative Ce anomaly is evidence of an early stage of weathering (Patino et al. 2003). Similar weathering processes related to the development of abnormal trace element abundances are observed also in few meteorites weathered in Antarctic environment (e.g., Koeberl and Cassidy 1991, Crozaz et al. 2003). The primary carriers of REE in eucrites are mesostasis phosphates (Delaney et al. 1984). 23 As discussed previously, identified secondary minerals in terrestrial rocks that include REE with abnormal characteristics are phosphates. Because of that, one of the working hypotheses for this study was that REE carrying phase in the EET79004 will also be phosphates. SEM and EDS was proven to be a sufficient method of identification of those minerals in the study of weathered terrestrial basalt by Wade (2002). However, a very detailed search for those phases revealed only two occurrences of very small phosphates in minute veins (one of them shown on Appendix 1 Figure 3). The identified phosphate vein fillings are too small to have their chemical composition (except for high P content) characterized by EDS. However their light color in the BSE image suggests that those phases consist of elements with relatively high atomic numbers that could be REE (similarly to ones found by Wade (2002)). Because it was not possible to detect REE in the phosphate veins fillings or to measure their chemical composition, it is not possible to determine if the amount of identified phosphate minerals would be enough to produce observed abnormal REE patterns. Phosphate phases (potentially REE-bearing) are distributed non-unifome within the sample — both identified occurrences are in close proximity to each other and within the same plagioclase gain. Similarly, REE patterns of the same meteorite, but different samples, can be very different (Mittlefehldt and Lindstrom 1991, Warren and Jerde 1987) which shows that weathering effects are not unifonnly distributed within the meteorite. It is possible that the split analyzed by Mittlefehldt and Lindstrom (1991) and characterized by abnormal REE patterns is different from the one analyzed in this study. This is one possible reason explaining why more phosphates (potentially REE-bearing) were not found. 24 The textural evidence for a terrestrial weathering origin of P-rich phases is not conclusive. Those phases are located inside small veins that are cross-cut by the S-rich vein, meaning that P-veins are older than S-rich veins (Appendix 1 Figure 18). It is not possible to determine if P-rich phases are pre-terrestrial. Gypsum can sometimes contain sigrificant amounts of REE (terrestrial: Playa et al. 2007; Martian: Bridges and Grady 2000). However in other occurrences, the amount of REE in sulfates is much lower (e.g., Toulkeridis et al. 1998, Papike and Burger 2008). Unfortunately, because the trace-element chemical composition of the sulfate veins was not determined, it is impossible to determine if sulfates were REE carriers in EET79004. If the S-rich phase is also the most important secondary mineral that includes REE, it could explain unusual REE patterns observed by Mittlefehldt & Lindstrom (1991). The present study was not sufficient to identify the phases responsible for the anomalous REE pattern. Methods previously satisfactory applied in a similar study of terrestrial basalts (Wade 2002) were not adequate to accomplish the same goal in EET79004. This is caused either by the small size or heterogeneous distribution of weathering phases within the meteorite. If the former is true, further study would require more detailed examination of the same sample using instruments with better spatial resolution and lower detection limits. The latter is supported by published findings of heterogeneous weathering (Mittlefehldt and Lindstrom 1991, Warren and Jerde 1987) and if true would require examining many more thin sections of the same meteorite. Of course, it is also possible that it is a combination of those two scenarios. 25 Ni-rich phases present in vesicles (Appendix 1 Figure 2, Appendix 1 Figure 13) are definitely terrestrial in origin because they postdate creation of fusion crust. However, they do not represent a weathering phase — weathering in oxidizing terrestrial conditions could not create a pure Ni rich phase. The Ni-rich phase is probably representing phases condensated from vapor created during atmospheric entry. Similar, euhedral crystals of pyroxene have been observed previously by S. McKay (Taylor 1982, figure 4.14). Conclusions 1. The outer most layer (3-4 mm) below the fusion crust of EET79004 has its properties extensively modified by weathering — especially with respect to S redistribution. The outer-most layer includes sigrificant amounts of evaporite minerals (mostly Ca—sulfates). Vesicles fiom the fusion crust are filled with two types of terrestrial weathering phases; large euhedral tabular Ca-S phases and small microcrystalline or amorphous K-S phases. Secondary REE carrying phases were not fully identified. Phosphate veins are one possible choice, although REE can also be hosted in sulfates. EET79004 is not marked with “e” in the ANSMET classification database. However it includes evaporites. It is reasonable to assume that it is not the only case of such an occurrence, and a larger number of meteorites contains evaporites than are indicated in the AN SMET classification database. 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It I . ...... . .x.. . . .. 0 .0 . . .. Hr . ,u ,. c 0.. .- .. . 3 . . . .... . .. I . 0. ll . o. s k U 0 v. u. . n .u . .0 n at . . . . . .0 .. . .7. . .. \1 . av J)”. 0 l o a . 0.. .fl/ . ... S \s . . ... . u .. . ... r. .. n .0 .- ...A ....J. \ 1 .v . ...:I an... vb I“ 45 REFERENCES Antarctic Meteorite Newsletter, 1980, 3(3), 6. http://curator.j sc.nasa.gov/antmet/amn/previous_newsletters/ANTARTIC_ME TERORITE_NEWSLETTER_VOL_3_NUMBER_3.pdf Banfield J .F. and Eggleton RA, 1989, Apatite replacement and rare earth mobilization, fractionation, and fixation during weathering. Clays and Clay Minerals 37(2), 1 13-127. Barrat J.A., Jambon A., Bohn M., Blichert-Toft J., Sautter V., Goepel C., Gillet P., Boudouma O. and Keller F., 2003, Petrology and geochemistry of the unbrecciated achondrite Northwest Africa 1240 (NWA 1240); an HED parent body impact melt. Geochimica et Cosmochimica Acta 6 7(20), 3959-3970. Bridges J.C. and Grady M.M., 2000, Evaporite mineral assemblages in the nakhlite (martian) meteorites. Earth and Planetary Science Letters 1 76, 267-279 Campbell LB. and Claridge G.G.C., 1987, Antarctica: Soils, Weathering Processes and Environment. Elsevier Developments in Soil Science 16, 1-368. Cotten J, Le Dez A., Bau M., Carofi M., Maury R.C., Dulski P., Fourcade S., Bohn M. and Brousse R., 1995, Origin of anomalous rare-earth element and yttrium enrichments in subaerially exposed basalts; evidence from French Polynesia. Chemical Geology 119(1-4), 115-138. Crozaz G., Floss C. and Wadhwa M., 2003, Chemical alteration and REE mobilization in meteorites fi‘om hot and cold deserts. Geochimica et Cosmochimica Acta 6 7(24), 4727-4741. Delaney J .S., Prinz M., Nehru C. and O’Neill C., 1982, The polymict eucrites Elephant Moraine A79004 and A7901] and the regolith history of a basaltic achondrite parent body (abstr.) 13th LPSC, Journal of Geophysical Research 87, A339- A352. Delaney J.S., O’Neill C., Prinz M., 1984, Phosphate minerals in eucrites (abstr.). 25’hLPSC, 208-209. Drake M.J., 2001, The eucrite/Vesta story. Meteoritics & Planetary Science 36(4), 501- 5 13 . Dufresne ER. and Anders E., 1961, On the chemical evolution of the carbonaceous chondrites. Geochimica et Cosmochimica Acta 26, 1085-1114. Hutchinson R., 2004, Meteorites: A petrologic, chemical and Isotopic Synthesis. Cambridge University Press, Cambridge. 46 Jull A.J.T., Cheng S., Gooding J.L., Velbel MA. 1988, Rapid growth of magnesium- carbonate weathering products in a stony meteorite from Antarctica. Science 242, 417-419. Gooding J.L., 1981a, Mineralogical Changes during Terrestrial Weathering of Antarctic Chondrites. 12th LPSC, 350-353. Gooding J. L., 1981b, Mineralogical aspects of terrestrial weathering effects in chondrites from Allen Hills, Antarctica. 12’h LPSC, 1105-1122. Gooding J.L., 1989, Significance of Terrestrial Weathering Effects in Antarctic Meteorites. Smithsonian Contributions to the Earth Sciences 28, 93-98. Gounelle M. and Zolensky ME, 2001, A terrestrial origin for sulfate veins in C11 chondrites. Meteoritisc and Planetary Science 36, 1321-1329. Kelly WC. and Zumberge J .H., 1961, Weathering of a quartz diorite at Marble Point, McMurdo Sound, Antarctica. Journal of Geology 69(4), 433-446. Klimchouk A.B., 2000, Dissolution and conversions of gypsum and anhydrite. Speleogenesis evolution of karst aquifers, 160-168. Koeberl C. and Cassidy W.A., 1991, Differences between Antarctic and non-Antarctic meteorites; an assessment, Geochimica et Cosmochimica Acta 55(1), p.3-l 8. Mittlefehldt D.W., McCoy T.J., Goodrich CA. and Kracher A., 1998, Non-chondritic meteorites from asteroidal bodies. Reviews in Mineralogy 3 6, 4.1-4.195. Mittlefehldt D.W. and Lindstrom M.M., 1991, Generation of abnormal trace element abundances in Antarctic eucrites by weathering processes. Geochimica et Cosmochimica Acta 55, 77-87. Lee MR. and Bland P.A., 2004, Mechanism of weathering of meteorites recovered from hot and clod deserts and the formation of phyllosilicates. Geochimica et Cosmochimica Acta 68, 893-916. Losiak A. and MA. Velbel, 2009, Geographic influences on evaporite formation during weathering of Antarctic Meteorites. 40’” LPSC, abstract No. 1394. Papike J .J ., Burger P.V., Kamer J .M. and Shearer GK, 2008, Martian Sulfates: Gypsum Crystal Chemistry and Characterization of Two Terrestrial Analogs. Ground Truth From Mars LPI Contribution No. 1401, 83-84. Patino L.C., Velbel M.A., Price J .R. and Wade J .A., 2003, Trace element mobility during spheroidal weathering of basalts and andesites in Hawaii and Guatemala. Chemical Geology 202(3-4), 343-364. 47 Playa E., Cendon D.I., Trave A., Chiva AR. and Garcia A., 2007, Non-marine evaporites with both inherited marine and continental signatures; the Gulf of Carpentaria, Australia, at approximately 70 ka. Sedimentary Geology 201 (3- 4),267-285. Richardson S.M., 1978, Vein formation in the C11 carbonaceous chondrites. Meteoritics 13, 141-159. Ruzicka A., 1995, Nullarbor 018: A new L6 chondrite from Australia Meteoritics 30, 102-105. Shimizu H., Masuda A. and Tanaka T., 1983, Cerium anomaly in REE pattern of Antarctic eucrite. Memoirs of National Institute of Polar Research Special Issue 30, 341-348, Sykes M.V. and Vilas F., 2001, Closing in on HED meteorite sources. Earth Planets Space 53, 1077-1083. Takeda H., 1997, Mineralogical records of early planetary processes on the howardite, eucrite diogenite parent body with reference to Vesta. Meteoritics and Planetary Science 32, 841-853. Taunton A.B., Welch SA. and Banfield J .F ., 2000, Microbial controls on phosphate and lanthanide distributions during granite weathering and soil formation. Chemical Geology 169(3-4), 371-382. Taylor SR, 1982, Planetary Science: A Lunar Perspective. Lunar and Planetary Institute, Houston. Toulkeridis T., Podwojewski P. and Clauer N., 1998, Tracing the source of gypsum in New Caledonian soils by REE contents and S-Sr isotopic compositions. Chemical Geology 145(1), 61 -71. Velbel, M.A., 1988, The Distribution and Significance of Evaporitic Weathering Products on Antarctic Meteorites. Meteoritisc 23, 151-159. Velbel M.A., Long D.T. and Gooding J.L., 1991, Terrestrial weathering of Antarctic stone meteorites: Formation of Mg-carbonates on ordinary chondrites. Geochimica et Cosmochimica Acta 55, 67-76. Wade J .A., 2002, Element mobility and secondary mineral formation during the early stages of alteration in rocks from the Tecuarnburro volcanic complex, Southeast Guatemala. Thesis (M.S.), Michigan State University. Dept. of Geological Sciences Warren RH. and Jerde E.A., 1987, Composition and origin of Nuevo Laredo trend eucrites. Geochimica et Cosmochimica Acta 51, 713-725. 48 Wentworth SJ. and Gooding J .L, 1991, Carbonate and sulfate minerals in the Chassigny Meteorite, Meteoritics 26(4), 408-409. Wentworth S.J., Gibson E.K., Velbel MA. and McKay D.S., 2005, Antarctic Dry Valleys and indigenous weathering in Mars meteorites: Implications for water and life on Mars. Icarus I 74, 383-395. Zolensky ME. and McSween H.Y.Jr., 1988, Aqueous alteration. In Meteorites and the Early Solar System (eds. J .F. Ker-ridge and MS. Matthews), 114-143, Univ. Arizona Press, Tuscon Arizona, USA. 49 EVAPORITE FORMATION DURING THE WEATHERING OF ANTARCTIC METEORIT ES — A WEATHERING CENSUS ANALYSIS BASED ON THE ANSMET DATABASE Abstract Weathering of meteorites at the scale of the entire Antarctic Search for Meteorites program population is studied by analyzing the most recent version of the online Antarctic meteorite classification database that includes information about 15,263 meteorites. This paper updates, supplements and expands on the last Antarctic meteorite weathering census by Velbel (1988, Meteoritics 23, 151-159). On average 5% of all Antarctic meteorites are marked as evaporite-bearing in the Antarctic Meteorite Database. Evaporite formation depends on compositional group, for example, is much higher for C chondrites than for ordinary chondrites, supporting the findings of Velbel (1988). Ordinary chondrites of petrologic type 3 more often have evaporites on their surface than meteorites of other petrologic types. There is no apparent relation between evaporite formation and meteorite rustiness, which contradicts the findings of Velbel (1988). Some meteorite-bearing fields influence the frequency of evaporite-mineral formation on meteorites. The influence of location is apparently related to differences in environmental conditions most probably microclimate or/and hydrologic conditions. There is no relation between abundance of evaporite-bearing meteorites and distance from the sea. Evaporite formation varies with year of collection; however it was not 50 possible to distinguish if this is more related to annual changes in environment or an artifact of sample categorization or curation. Introduction There are two main types of weathering products on Antarctic meteorites that are visible at the hand-sample scale: rust and evaporites. Although many scientific papers discussed problems related to the weathering of Antarctic meteorites (e.g., Gooding 1981 , Gooding 1986, Harvey and Score 1991, Mittlefehldt and Lindstrom 1991, Benoit and Sears 1999, Crozaz Floss and Wadhwa 2003, Lee and Bland 2004, Tyra et a1. 2007), only a few articles have been published about evaporitic products of Antarctic weathering (e.g., Marvin 1980, Velbel 1988, Jul] et al. 1988, Velbel et al. 1991, Gounelle and Zolensky 2001). Evaporites are highly water soluble minerals, formed as a result of the evaporation of bodies of water. Although annual average air temperatures in Antarctic meteorite-bearing ice fields are below 0°C (Comiso 2000), liquid water can exist inside the dark colored rocks during the summer (Schultz 1986), as well as capillary water or thin films (e.g., Campbell and Claridge 1987, Gooding 1981, 1986). Sometimes the amounts of water can be significant; for example Cassidy (2003) reported a large meltwater pond in the area of the Lewis Cliff meteorite-bearing field (although it was frozen during the time of expedition). Based on the carbon isotopic composition of carbonate evaporites were formed in temperature between -2 i4°C (Grady et al. 1989). 51 Evaporitic materials on Antarctic meteorites consist of mainly Mg and Ca carbonates and sulfates (e.g., nesquehonite Mg(HCO3)(OH)-2H20, hydromagnesite Mg5(CO3)4(OH)2-4HZO, epsomite MgSO4-7H20, starkeyite MgSO4-4H20, gypsum CaSO4-2H20, amorphous Mg-carbonate, as well as various unidentified K, Fe and Mg sulfates (V elbel 1988 and references therein)). Cations, especially Mg, present in evaporites probably come from the weathering of primary minerals present in meteorites (most likely olivine) (V elbel et al. 1991). Carbon dioxide that forms carbonates originates from the Earth’s atmosphere (e.g., Jull et al. 1998), although some part of it may also come from extraterrestrial sources by way of the meteoritic indigenous carbon (Tyra et al. 2007). The source of other anions is still not entirely clear. The Antarctic Search for Meteorites (AN SMET) program of United States of America began in 1976 (Harvey 2003). The recent version of ANSMET database includes information on meteorites recovered up to 2006 (although sample processing and data entry from 2005 and 2006 is not complete). During the 32 field seasons (one in 1989 was canceled due to weather conditions) meteorites were found in 48 different locations, some of which were visited in multiple field seasons (Harvey 2003). Two or three meteorite-bearing fields were visited during most years. Specimens collected by AN SMET are curated at Antarctic Meteorite Curation Facility at the Johnson Space Center in Houston, Texas. Meteorites are available for study to the entire scientific community. Only one previous article (Velbel 1988) has discussed weathering based on data from the entire available population of Antarctic meteorites. It was written more than 20 years ago and at that time, data for only about 1367 meteorites were available, of which 52 74 had evaporites. At this writing, the AN SMET database includes information on 15,263 meteorites, of which 757 meteorites have evaporites. This is more than a ten-fold increase in the number of available meteorites since the last such population study, allowing for much more complete analysis. Additionally, the large number of meteorites with evaporites allows more detailed analysis of evaporite formation with respect to a larger variety of factors than previously possible. The aim of this paper is to update, supplement and expand on the last Antarctic meteorite weathering census by Velbel (1988), by examining five possible influences of the frequency of evaporite formation by weathering in the population of ANSMET Antarctic meteorites: 1) Meteorite compositional class, 2) Meteorite petrologic type, 3) The weathering classification, 4) The geographic locations of meteorite-bearing ice fields, 5) The year of collection. Methods Data on evaporite distribution on Antarctic meteorites recovered by the ANSMET program were retrieved from the most recent available version (downloaded on 12.10.2008) of the online Antarctic meteorite classification database on the NASA Astromaterials Curation web page (http://curator.isc.nasa.gov/antmet/). Based on this 53 database, information about the total number of meteorites, the number of meteorites with evaporites, the year of collection, the weathering category and the petrologic type was determined. In order to facilitate analysis, data on the following population attributes were tabulated: a total number of meteorites, and number and percentage of evaporite bearing meteorites with respect to four variables (meteorite compositional class, meteorite weathering classification, meteorite-bearing field and the year of collection). All meteorites were treated as separate specimens; pairing was not taken into account, however some results in respect to pairing were tabulated (Appendix 4). Results in respect to all parameters were recorded, but for further analysis only subgroups more numerous than 20 (or more — if indicated in footnotes) specimens were used. The number of 20 meteorites was arbitrarily assumed to be in sufficient to allow the analysis. The characteristics of the data available do not allows for applying advanced statistical methods to test confidence levels for different populations. The AN SMET database data analyzed in the study is a nominal data (meteorite classification, geographic location of meteorite-bearing ice fields, the year of collection) and only part of it can be treated as partially ordinal data (petrologic type and weathering classification). Organizing the data with respect to factors that are known to influence evaporite formation on Antarctic meteorites allowed identifying the influence of individual weathering-controlling factors. Velbel (1988) showed that the probability of evaporite occurrence is related to the compositional classification, and because of that, in a present study, all other factors were always reported relative to composition. Some of the tables were also organized relative to other factors that influence evaporite occurrence (location and year of collection), to examine the influence of individual factors. After 54 implementing these procedures, in most of cases only ordinary chondrites were numerous enough to allow for analysis. Confidence levels were in all cases calculated for 95% probability using MINITAB. Usage of some more advances statistical tests (e.g., chi- square test) have been explored and initially applied. However, because of large differences between numbers of meteorites within groups as well as large numbers of samples in some of the groups, tests cannot be fully reliable. Results The most recent version of AN SMET database includes information about 15263 meteorites: 14374 (94.2%) chondrites, 411 (2.7%) achondrites, and 163 (1.1%) irons and stony-irons. The database does not contain information about the classification of 315 meteorites (2.1%). Approximately 5.0% (757) of all US. Antarctic meteorites have evaporites. This is consistent with previous findings (5.4% in Velbel 1988). Influence of meteorite composition (class) Characteristics of meteorites such as chemical composition (Table 1) and porosity (Table 2) depend on their classification. Similarly, the proportion of meteorites with evaporites varies with composition (classification), consistent with Velbel’s (1988) findings (Table 3, Table 5) that attributed those differences to the differences in chemical composition. The carbonaceous chondrite population has the highest percentage of evaporite bearing meteorites (29.2%); achondrites have intermediate abundance (6.6%), and ordinary chondrites the lowest (4.0%). Calculated confidence intervals show that with 95% probability the percent of evaporite bearing meteorites differs within those 55 groups. Due to the larger number of available specimens it was possible to differentiate between the percent of evaporite-bearing meteorites among different meteorite groups, while in the previous study (V elbel 1988) only classes could be compared (with exception for H, L and LL ordinary chondrites). For example, there is a significant variability within carbonaceous chondrites class; 54.2% of Karoonda-type carbonaceous chondrites have evaporites, while for Renazzo-type carbonaceous chondrites the evaporite-bearing fraction is only 10.9%. Within the ordinary chondrite group there are some important variations in the percent of evaporite bearing meteorites. 5.3% of H- chondrites have evaporites on them, compared with only 1.7% of LL chondrites. In general, percentages of evaporite bearing meteorites vary between Velbel (1988) and the present study. For example, the percentage of evaporite-bearing meteorites reported by Velbel (1988) and this study are respectively 53.8% and 29.2% for C chondrites, and 5.1% and 4.2% for L chondrites. Based on present study 5.3% of H chondrites have evaporites, while in Velbel (1988) it was 3.6%. However, despite these differences, the general relations between different classes and groups remained the same, and differences are within confidence intervals: C chondrites in Velbel (1988) and present study are the meteorite class that contains the highest percent of evaporite-bearing meteorites, while L and H groups have much lower and similar percentages of evaporite-bearing meteorites. 56 Table 1 Percent of evaporite-bearing meteorites, and average weight percent of chosen elements in relation to meteorite classification. Data about chemical composition from Hutchison 2004, Table 2.1. O 0 Name Symbol otal Ev. % Ev. S A A Enstatite E 102 1 18. 0.4% H Chondrites H 4908 258 5.3 0.1% L Chondrites L 4 0.1% LL Chondrites LL 2985 52 1. 0.1% 161 24 . 2.2% CV 37 24. 0.6% Renazzo . . 1.4% 20 15. . 0.5% Karoonda 83 54 . 0.1% Iron 1 0. . 0.8% 0. 1. 1. 1. 1. 1. 1. 1. 1. 1. Table 2 Average porosity of meteorite groups based on published data for meteorite falls (Corrigan et al. 1997, Consolmagno et al. 1998, Flynn et al. 1999, Britt and Consolmagno 2003, Wilkison et al. 2003) (full data in Appendix 2). Information about porosity of other meteorite groups is not available at this point. . St. # of Group Porosrty Dev. measurements H 6.4 6.3 64 L 5.2 6.1 102 LL 7.4 5.4 15 CM 20.7 7.6 10 CV 14.3 7.7 24 Achondrites 6.2 4.3 15 57 P3 the amos 53116 pal“ Shows per evaporites [he grOUp number in 1111120531- l‘lt ex'aPOriIeS comia‘OSitiC Infillence ' T petrologic gTOUPS W11 percent 0f areex'aP'Ori those 010 I assume that this group 1 paper. Fore in the LE‘ Additionally also Seems t Paired samples are thought to come from the same meteorite that disintegrated in the atmosphere. The chemical composition and terrestrial age of meteorites within the same pairing group is the same, but their terrestrial history could be different. Appendix 4 shows percent of evaporite bearing meteorites within the pairing group. If formation of evaporites on Antarctic meteorites was fully dependent on composition all meteorites in the group should have 100% o 0% evaporites. Unfortunately, because of low sample number in most of the pairing groups making a statistically meaningful comparison is impossible. However within the EET90053 L6 group 2.1% of 678 meteorites had evaporites visible on their surface. This falls slightly below values for L chondrites compositional group. Influence of petrologic type Table 4 presents the percentage of evaporite-bearing meteorites in different petrologic types. For all analyzed compositional groups (results for other meteorite groups with small populations are not shown here) petrologic type 3 has the highest percent of evaporite-bearing meteorites. For the total population of LL chondrites 1.7% are evaporite-bearing, whereas 16.1% of LL33 are evaporite bearing. Estimated errors for those two populations are not overlapping (with 95% probability) so it is reasonable to assume that they are in fact different. The relatively small number of available samples in this group makes it highly susceptible to the influence of other factors discussed in this paper. For example; three out of five meteorites that had evaporites on them were found in the LEW field. This location seems to favor evaporite formation (Table 6). Additionally, three evaporite bearing LL3 meteorites were found in 1988, a year which also seems to be characterized by overabundance of evaporite-bearing meteorites (Table 59 0.0-. .-1 '.’Jo .— 7). Those three meteorites have not been paired yet - although they have relatively similar properties and it cannot be excluded that they should be paired. However, even if we treat those three specimens as one, so that the total number of evaporite-bearing LL3 chondrites is three, these paired evaporite-bearing LL3s still consist of 9.6% of total number of LL3s. Similarly, in the H group four out of seven evaporite-bearing meteorites of petrologic type 3 were also collected in 1988 at LEW ice field. When corrected for possible pairing (counting all these meteorites as one) the percentage of evaporite-bearing meteorites is 7.1% which is still higher than for H chondrites any other petrologic type. L chondrites are the most numerous. Out of total number of 235 L3 21 have evaporites (8.9%) while the average for the entire population of L chondrites is only 4.2%. Table 4 also includes information about the percent of evaporite-bearing meteorites in relation to petrologic type and weathering category. The relatively small numbers of specimens in each category preclude statistical comparisons; no trends between weathering categories are apparent. Table 4 Percent of evaporite-bearing meteorites with respect to petrologic types and weathering category of LL, L and H chondrites. Petrologic type Total Ev. % me - me + LL 2985 52 1 .7% 1. 3% 2. 3% LL3 31 5 16.1 % 5. 5% 33. 7% LL4 56 0 0.0% 0.0% 5. 2% LL5 2229 28 1.3% 0. 8% 1. 8% LL6 664 19 2.9% 1. 7% 4.4% L 5880 246 4.2% 3. 7% 4. 7% L3 235 21 8.9% 5. 6% 13.3% L4 290 12 4.1% 2. 2% 7. 1% L5 2292 96 4.2% 3.4% 5.1% L6 3050 115 3.8% 3.1% 4. 5% H 4908 258 5.3% 4. 6% 5. 9% H3 56 7 12.5% 5.2% 24. 1% H4 308 19 6.2% 3. 8% 9. 5% H5 2877 137 4.8% 4. 0% 5. 5% H6 1649 94 5.7% 4. 6% 6. 9% 60 Influence of weathering (rust) index Paired groups of meteorites usually do not fall into uniform weathering group (Appendix 4). Usually weathering groups are closely related (e.g., A/B and B, or B, B/C and C for one paired group. However there are groups (e.g., GRA98019 or EET96135) that include samples of 4 different weathering groups. The influence of weathering category on the frequency of evaporite formation in the ANSMET population of Antarctic meteorites is not apparent (Table 3, Table 5). There is no common trend of increase/decrease in percentage of evaporite-bearing meteorites with weathering category consistent among all compositional groups. The percent of evaporite bearing samples varies widely within compositional-weathering groups and confidence levels of different weathering group overlap. For example, 1.2% of H chondrites of weathering category A/B have evaporites, compared with 8.8% of those in weathering category B/C. Similarly, evaporite-bearing L chondrites constitute 5.4% weathering category A and around 3% for A/B and C. When considering only groups based on composition and weathering that are more numerous than 20 meteorites (marked by white type on the Table 3) a very weak trend appears in which the percentage of evaporites in the group varies irregularly. It is high for the group A and WC and lower for NE, B, and C. However, this trend is not shared by compositionally close groups as would be expected. For example, in the class of ordinary chondrites, H chondrites have distinctly higher percentage of evaporite-bearing meteorites in B/C group, while for L chondrites the highest percent of evaporite-bearing meteorites is present in both A and B/C weathering groups. The limited number of available meteorites in some classes and weathering groups limits the number of instances for which inferences can be drawn. 61 Table 5 presents results aggregated in a way consistent with Table 4 from Velbel (1988). Comparison reveals a large discrepancy in percentages of evaporite- bearing meteorites between this and the previous study. Velbel (1988) reported 85.7% of C chondrites of A weathering category had evaporites on them, while in this study the value is only 32%. This difference is probably at least partially related to the much smaller number of C chondrites samples available at the time of the previous study. Velbel (1988) observed that for the carbonaceous chondrites “significant evaporite formation is correlated with the earliest stages of rusting”, but the results of the present study do not support this. The percentage of evaporite-bearing C chondrites varies around 30%, as low as 16.9% for weathering category B/C andas high as 40.5% for weathering category C. The discrepancy is lower for L and H chondrites where for both studies values vary between 2 and 8%. Table 5 contains information about evaporite-bearing meteorites for classes of ordinary chondrites controlled for petrologic class. No obvious trends are apparent. Making comparisons within same compositional group but different petrologic type is difficult because most of the meteorites are from petrologic type 5 or 6. in summary, no systematic relationship between weathering category and evaporite occurrence is evident for any meteorite class or group. Either those two parameters are not related, or different trends exist for all compositional groups. 62 tegories (Ev. rmg ca ), table outline is based on Velbel (1988) Table 4. armg Table 5 Evaporitic statistics in respect to meteorite groups and weathe evaporite be $ 0 .0 0 00 $0.0 0 00 $0.0 0 00.. $0.0 0 3 $5. 0 00 $0.0 00 :4 0005:0591 $0. 2. 0 0w $ 0 .00 0 00 $0.00 0 r0 $0.0v 0 0 $0.0 0 4 $0.0_. .00 00F m $0.0 00 0000 $00 03 000? $00 00 00 $0. — 0 00? $5 F 00 $0.0 000 000”. I $0.0 00 000 $0.0 0 03; $0.4 F0 00 F0 $0.0 F0 0.. Z $v.0 0 0E. $0.v 00 0000 ._ $0.0 0 0:. $0.? 0 00¢ $04 0F 3: $04 0w 3.3 $0.0 0 090 $0; 00 0000 .3 $0.04 0 F 00 $0.0F Z 00 $0.00 00 000 $0.00 00 00 $0.00 00 $0.00 03 000 o .06... .>m Eek $ :32. $ .>m .008 l .92. $ .>m 030% 0:20 o 20 m 02 .0qu 0000000 00005003 00000005. 63 Influence of geography Table 6 and Figure 5 show the percentage of evaporite-bearing meteorites as a function of their collecting area. Only ice fields from which a total of more than 100 meteorites have been recovered and classified are shown. Colors represent deviation in the proportion of evaporite-bearing meteorites from each ice field (as a fraction of all meteorites from the same ice field) from the average value calculated for entire population of a given type of meteorite. Values were calculated for the entire population (first 3 columns of Table 6) as well as for ordinary chondrites, the most abundant meteorite classes (to control for the composition). Some meteorite-bearing ice fields show consistently high (GRO, MIL) or low (DOM, LAP, MAC, MET, RBT) proportions (relative to the entire-population average) of evaporite-bearing meteorites, for all analyzed compositional groups (Losiak and Velbel, 2009). However, because of a small sample size the estimated errors are quite large for all compositionally controlled groups. On the other hand, the percentages of evaporite bearing meteorites in respect to total population, differ significantly, even considering the estimated error values. Other meteorite-bearing ice fields do not show such uniform over- or under-abundance of evaporite-bearing meteorites. In these cases, for the same field, evaporite-bearing meteorites are over-abundant relative to the population mean for some of the analyzed compositional groups, while meteorites of other compositions show lower-than-average proportions of evaporite bearing meteorites (e.g., EET, PCA, QUE). Figure 5 shows location of meteorite-bearing ice fields and percent of evaporites present on meteorites collected from those fields. No apparent trend is observed; fields characterized by over and under abundance of evaporite-bearing meteorites can be 64 located in close proximity to each other. For example, DOM ice field characterized by the lowest average percent of evaporites (0.7%), is neighboring GRO field that has the highest average percent of evaporite-bearing meteorites (13.5%). 65 .. ..19‘1. 1.1....1?‘ . fig. ...; 1 Figure 5 Map of meteorite fields on Antarctica (Losiak and Velbel 2009). Colors represent deviation from the average number of meteorites with evaporites — scale is consistent with one presented in table 1), a) statistics for all meteorites found in a specific field, b) statistics only for H chondrites, c) statistics only for L chondrites, d) statistics only for LL chondrites. 67 Figure 5 continuation. Influence of year of collection Year of collection influences the frequency of evaporite formation in the ANSMET a population of Antarctic meteorites. Table 7 presents percentages of evaporite-bearing classes of ordinary chondrites with respect to year in which they were found. Color coding (using the same conventions as in Table 6) shows relative increase/decrease in percent of evaporite-bearing meteorites in relation to average value in every given year (for compositionally controlled groups). The percentage of meteorites with evaporites in different years varies between 0.6% in 2004 to as much as 11.9% in 68 1995, those values are significantly different. Some years (1978, 1981, 1983, 1997, 1999, 2000, 2002, and 2004) show, for all compositional groups as well as for total population, lower than average percentages of evaporite-bearing meteorites. Other years (1988, 1993, 1994, 1995, 2005) have greater than average proportion of meteorites with evaporites. However there are years in which some groups have higher and others lower than average percentage of evaporite-bearing meteorites (e.g., 2001), but at least in some cases it is caused by low number of collected specimens. 69 Inost)t hflfluenc influen influen unnpo llus a year c meteo goupt and 3 found fionil value: percei EET j belWe indnd adVar Each year meteorites are collected from only few meteorite-bearing fields (in most years meteorites collected are from one or two field areas). Because of this, the influence of collection year on percent of evaporite-bearing meteorites can be strongly influenced by geographical location (see previous section). To exclude the possible influence of location, data for L and H chondrites (the most numerous meteorite compositional groups) were arranged according to year and field of collection (Table 8). This allows comparing the influence of both variables. Results from Table 8 shows that year of collections influences evaporite occurrence. Percentages of evaporite-bearing meteorites are much more similar to each other within yearly groups than within location groups. For example, the evaporite-bearing fraction of L chondrites in 1987 was 3.6% and 3.0%, for 1990 2.6% and 3.8%, and for 2004 no meteorites with evaporites were found in any of the collected field areas. Year 2003 is unique because 1.2% meteorites from LAP and 19.8% meteorites fi'om GRO fields had evaporites. However, both of those values are higher than the long term field averages. Within L chondrites, variation within percentage of evaporite-bearing meteorites within one field (but different years) is for EET 2.6% and 4.1%, LEW 3.0% and 7.8% QUE 0.9% and 6.5%. Within-year variations between different collecting areas are smaller than between-year variations within individual collecting areas, however in order to properly test this hypothesis more advanced statistical tests (e.g., chi-square test) should be applied in the future. 71 Table 9 shows changes in staff making primary analysis of the meteorites collected by the ANSMET program (Antarctic Meteorites Newsletter 1978-2007). Staff analyzing meteorites were not changing abruptly and always at least one very experienced lab technician was present. New people were not allowed to do analyses independently for at least a year. Table 9 List of the AN SMET laboratory staff through time. Sample 777879808182838485868788899091929394959697989900010203040506 8. Mason A. Reid R.S. Clarke R. Score C. Schwarz G. MacPherson J. R. Martinez E. C. Satterwhite P. Warren R. Buchwald R. Marlow D. Mittlefehldt M. Lindstrom K. McBride Tim L Welzenbach G. Benedix Cari Lisa Collins V. E.Buflock L LaCroix G. MacPherson R. R. M. Fries 73 Discussion Influence of composition (class) Meteorite compositional group influences the frequency of evaporite formation in the AN SMET population of Antarctic meteorites. Different compositional groups are characterized by varying percentages of evaporite-bearing meteorites (Table 3). Additionally, if a sample size is larger than 20 specimens, it is clear that percentage of evaporite-bearing meteorites is more similar within individual compositional classes, than between compositional classes. For example, percentages of evaporite-bearing meteorites among different ordinary chondrite groups vary between 1.7 and 5.3% with an average of 4.0%, while within carbonaceous chondrite class proportions vary between 10.0 and 54.2% with an average of 29.2% (Figure 6). Groups with similar composition (i.e., from the same class) have similar fiequencies of evaporite occurrence, demonstrating that the differences are not random. Differences in percentages of evaporites-bearing meteorites are related 'to the differences in chemical and physical characteristics of meteorite groups. The meteorite classification is based on chemical characteristics (Hutchison 2004); it is thus reasonable to assume that differences in evaporite percentages between compositional groups are due to differences in their chemical properties (as it was previously proposed by Velbel 1988). Figure 7 shows percentages of evaporite-bearing meteorites with respect to bulk chemistry, specially the weight percent of elements that form the main evaporite minerals. No relationship is apparent. Many evaporites found on Antarctic meteorites are sulfates; however sulfur contents are relatively uniform in all meteorite groups and do not correlate with percent of evaporite-bearing meteorites. Similarly, there seems to be no 74 relationship with bulk Mg and Ca content. Carbon content and percentage of evaporite- bearing meteorites in ordinary chondrites is on average much lower than in carbonaceous chondrites; however, within the C chondrites group, higher weight percent C does not correlate with increased susceptibility to evaporite formation. However, it has been shown that the carbon in the evaporitic minerals is terrestrial (Gooding et al. 1988, Jull et al. 1988, Grady et al. 1989). 7S Percent of meteor 6096 83 5096 4096 3096 161 37 20% 102 20 i 49085850 [.1985- 0%5 , a) m m 0 to -q-) o O m to C C ‘- U W m "’ Eggggcgmggfiefc’mfigsg c..: O: .E > no ‘- m C O ..D — H .: LU L “cc: Emmohum cm: 3 O o o ">- c: (‘0 5 '5': O 3 LI. LU .5 5 6 x m '8 o a :1: II -' j °Z° 3 OdeBFY Ca rbonaceous chondrites chondrhes Chondrites Figure 6 Percent of meteorites with evaporites as a firnction of compositional group. The das Antarctic meteorites (5%). Numbers refer to the total number of meteorites from a given gror 76 with evaporites 0.03.6 0230 .650 000.: >090 mco: 80.60050 0.: 19 S7 mtmcoczs machEm 3:004. 03:65 80:200.. 0:830 84. 8:53. 00:00 0.: 22>. 00007005 8:3me 303000050 Achondrites ne represents average percentage of evaporite bearing meteorites for entire population of nd in Antarctica. The weathering rate can depend more on the mineral assemblage than on the bulk chemistry, e.g., the Fe—rich variety of olivine weathers much faster than Mg-rich olivine (e.g., Velbel 1999). Meteorites of relatively similar bulk chemistry can be composed of different mineral assemblages and this can be a source of differences in percentages of evaporite-bearing meteorites among compositional groups (Hutchison 2004), although at present this relationship is not clear. 77 It is known that physical properties (especially porosity) of meteorites can influence the weathering rate of meteorites due to associated differences in ability of water to penetrate inside the rock (Bland et al. 2000). Porosity measurements (Table 2 and Appendix 2, Corrigan et al. 1997, Consolmagno et al. 1998, Flynn et al. 1999, Britt and Consolmagno 2003, Wilkison et al. 2003) show that the average porosity of C chondrites is higher than of ordinary chondrites. This is consistent with C chondrites having higher percentages of evaporite-bearing meteorites than ordinary chondrites (Table 3). Correlation of those variables is R2=0.839. More subtle differences in porosity do not show a similar relationship with evaporite occurrence (Figure 8). For example, if the evaporite formation was governed by porosity, we could expect that L chondrites, having the lowest porosity, would also have the lowest percentage of evaporite-bearing meteorites of the ordinary chondrite class; however, this is not the case. On the other hand, porosity measurements of meteorites are very imprecise (e.g., Wilkison et al. 2003), and even inter-meteorite variability is high, so the difference between LL and H chondrites may not be statistically significant. Additionally the correlation is controlled by just two groups of points of carbonaceous and ordinary chondrites (Figure 8). 79 Porosity vs % of evaporite bearing meteorites 30 R21=0339 U :5 20 o I L 3 15 / E / A LL 3: 10 / x CM ‘ )1: cv 5 fl 4 0.0 5.0 10.0 15.0 20.0 25.0 96 porocity Figure 8 Average porosity and percent of evaporite-bearing meteorites. A trend shows that, the higher the porosity, the more evaporates are present on the meteorite. Influence of petrologic type Meteorites of petrologic type 3 more commonly bear evaporites than meteorites of petrologic types 4, 5 and 6 (Table 4). This is consistent with findings of Velbel (1988) who suggested that meteorites of lower petrologic types have more evaporites. However, because of a small number of samples available at the time, he was able to observe only aggregated data (types 3 and 4 compared with petrologic types 5 and 6). The new data show that the above-average abundance of evaporite-bearing meteorites is related only to petrologic type 3. Low petrologic type meteorites include greater abundances of amorphous and poorly crystalline components than higher petrologic types (Hutchinson 2004). Velbel (1988) hypothesized that those components, being highly susceptible to weathering, can release their constitutuent atoms more readily, and that the rapidly released elements 80 become part of evaporite minerals. This study shows that even minor metamorphic reprocessing (associated with the change from petrologic type 3 to type 4) is sufficient to reprocess and render less reactive most of the phases that are highly susceptible to weathering. Influence of weathering classification No relationship between weathering classification and the frequency of evaporite formation in the AN SMET population of Antarctic meteorites can be discerned based on available data (Table 3). For most of the compositional-weathering groups the sample size is very small, which makes it very susceptible to the influence of other factors. Although the percentages of evaporite-bearing meteorites vary among weathering categories, there is no consistent trend of higher proportion of evaporite-bearing meteorites in the initial stages of weathering as suggested (for C chondrites) by Velbel (1988). Similarly, no other consistent trend is shared by all compositional groups. Although it is possible that all groups have their characteristic trends, this is unlikely because compositionally similar groups should behave similarly. Finally, a strong influence of other parameters may obscure systematic but weak evaporite-rust relationships. One of the suggestions for future work is to check if multiple generations of evaporites are present. Some of the groups (L, LL, CM) show a suggestion of a trend of abundant evaporite-bearing meteorites in the initial and late stages of rusting, however the relationship is weak. Perhaps one type of evaporite mineral is produced during early stages of weathering (weathering category A) and later removed (weathering category MB and B). Subsequently, in the final stages of weathering, development of a second 81 generation of perhaps compositionally different evaporites increases the proportion of evaporites in the higher-weathering category group bearing meteorites. To test this hypothesis it would be necessary to do a comparative study of composition of evaporite minerals from meteorites of the same group but different weathering categories. Influence of geography The geographic location of meteorite-bearing ice fields influences the frequency of evaporite formation on the AN SMET population of Antarctic meteorites (Table 10). If evaporite formation were fully controlled by composition, there should be no large differences in evaporite formation among different geographic ice-fields of origin for compositionally uniform populations. For example, for H chondrites the average number of meteorites with evaporites is 5.3% (of a population of 4908), and the proportion of evaporite-bearing H chondrites varies for different fields from less than 3% (RBT, ALH, DOM) to more than 9% (GRO, MIL, QUE). Similarly for L and LL chondrites, the percentage of meteorites with evaporites varies from less than 1% to 15.9% and from less than 1% to 8.3% respectively. The fact that some ice-fields show consistently above- average or below-average proportions of evaporite-bearing meteorites for all analyzed compositional classes of meteorites suggests that environmental characteristics at these sites favor the formation of evaporites. If the source of evaporites were terrestrial contamination such as sea salt, one might hypothesize that the number or proportion of evaporite-bearing meteorites decreases with increasing distance from the sea (Wentworth et a1. 2005). However results do not support this hypothesis (Figure 5). Fields with above- or below-abundances of evaporite-bearing meteorites seem to be distributed relatively randomly with distance 82 from marine coasts. This is consistent with previous results indicating that evaporites on Antarctic meteorites are not of terrestrial marine (e.g., sea salt) origin (V elbel et a1. 1991, Wentworth et al. 2005). Weathering rates of meteorites as well as type of processes depends mostly on climate (e.g., Bland et. a1 2000). It is thus reasonable to assume that the number of evaporite-bearing meteorites will depend on variation in climatic conditions. Meteorites collected from fields areas that have higher than average temperature (especially during the surmner — when liquid water can exist) should have more evaporite-bearing meteorites. Meteorite ice fields searched by AN SMET are located along Transantarctic Mountains (Harvey 2003), and all of them are situated at comparable altitude. Comiso (2000) produced Antarctic average monthly temperature maps for years 1979-1999 by modeling based on data from stations and infrared satellites. The maps show that (at the available scale and accuracy) climatic (temperature) conditions are similar for all meteorite fields. Additionally, some ice fields with higher-than—average abundances of evaporite-bearing meteorites (for all compositional groups) are immediate neighbors of those with lower-than-average proportions of evaporite-bearing meteorites (e.g. RBT, GRO, MAC (Figure 5)). Both observations preclude a macroclimatic influence. An alternative explanation is that environmental conditions at the micro-scale (e. g., microclimatic) are more important in evaporite formation. However, currently available data are not sufficient to test this hypothesis. Research would require setting automatic weather stations in meteorite-bearing fields characterized by over-, under- and average abundances of evaporite-bearing meteorites for at least one year. 83 The Lewis Cliff meteorite-bearing field (LEW) is one of the locations that are characterized by above-average proportion of evaporite-bearing materials (Table 6). The Lewis Cliff ice field consists of multiple collection sites (Cassidy 2003 pp. 297). ' Evaporites are present in this field not only on meteorites, but also in cracks in ice, in the moraine sediments and even around the meltwater ponds (Cassidy 2003). Fitzpartrick (1990) found nahcolite, trona borax and other associated minerals in samples from ice and moraine at the Lewis Cliff ice tongue. Trona existence is a result of the direct evaporation from standing water in lateral kettle ponds existing at this locality during the summer. Nahcolite has evaporated from waters rising from a point source (spring-like) beneath the ice. The amount and type of water should vary in response to characteristics of the environment (microclimate as well as type and location of basement rocks). If circulation of brine influences evaporite formation on meteorites it is reasonable to expect that, depending on the specific location within the meteorite field, the percent of evaporite-bearing meteorites will vary geographically (Table 10). In a population of H chondrites the number of evaporite-bearing meteorites coming from Meteorite Moraine is higher than for both Upper and Lower Ice Tongue (Figure 9). However the same trend is not present for L chondrites —- probably at least partially because of very low number (17) of available meteorites. 84 Upper Ice Tongue . Upper Ice Tongue Meteorite Moraine Figure 9 Location of sub-ice fields within the Lewis Cliff location (AMLAMP web page). Unfortunately, meteorites are usually collected only during few field seasons. Because of that, it is possible that the over- or under- abundance of evaporites in the specific field is not a result of influence of a field, but a consequence of collecting meteorites during limited number of years. However, Table 6 shows that some fields (LAP, GRO) have a consistent trend. 85 LEW ice field for H and L chondrites — only sites consisting of more than 100 meteorites Table 10 Percent of evaporite-bearing meteorites as a function of location within the in either H or L population were included. $0.0? $0.0 $0.0 0 00 $0.0F $0.0 $0.0 0 t. $0.0 $0.0 $0.0. Z 30 $0.0 $0.0 $0.0 0 0: $0.0 $0.0 $0.0~ 00 000 $000 $0.0 $0.00 0 00 $0.: $_.0 $0.0 00 000 $00 $0.0~ $0.0 00 000 $0.0 $0.0 $5. 3 000 $0.0 $0.0 $0.0 00 00: +2: .05 $ 50 62 +2: .9: $ 50 .02 +2: .9: $ .>0 .2 +2: .2. $ 50 .02 +9: .2: $ .>0 .2 E0 033 5:00 2:802 2:832 00008. 8_ .033 30:8 8_ 5%: .32 30.. 86 Influence of collection year The year of collection influences the frequency of evaporite occurrence in the ANSMET population of Antarctic meteorites. Some years show a consistent trend of higher or lower than usual percentage of evaporite-bearing meteorites for all analyzed compositional groups as well as for the entire population collected in a given year (Table 7, Figure 10). The most obvious variable that changes among different years is weather. The weather in Antarctica varies among years (Comiso 2000). Table 11 shows years in which it was especially warm or cold in January (summer) and July (winter) along with years in which no consistent trend was observed. For example, the higher than average January temperature does not correlate with higher (or lower) than usual evaporite- bearing meteorites. No other relation between those two variables is apparent. There may be a relation between temperature and evaporite formation. Alternatively, a temperature- evaporite abundance relation may be impossible to discern at the local level from average monthly temperatures known only at much larger scales (e.g., the scale of the continent). It is possible that evaporite development depends on maximal, not average temperatures or that only a few days of warm weather are sufficient to produce evaporite minerals. Once again, the available microclimatic data available are insufficient to test this hypothesis. 87 Percent of meteorites with evaporites 12.0% 10.0% I 8.0% I 6.0% 40% _ I1 I I I 20% 111. . || | I.I| 0.00/0 fir Tl 1 III III I III I TIT—III r I I I r I I TIT I 1 I III III III III III III III III T I (DIN00C)1"vaIOCDNQCDOPNC’DVI’WCONCOCDOFNMVWQ Nix-r0r000cocooooooooowoooommmmmmmmmmooooooo mmmmmmmmmmmmmmmmmmmmmmmmooooooo v-V-r-V-V-Pv-V-V-v-v-a-v-u-v-v-v-s—v-v-x—v-V-FNNNNNNN Figure 10 Percent of meteorite with evaporites for total population collected in given year. Years marked with gray have a total number of meteorites lower than 200. On the other hand other factors that vary between years can also have influence on the formation of evaporite minerals on meteorites. For example, meteorites collected during 2003 season were stored in a freezer that experienced a power loss (Antarctic Meteorite Newsletter 2006). One specific consequence noted by the curatorial staff was the appearance of evaporites. Thus, in this particular case, the higher-than-field-average evaporite abundances for 2003 acquisitions are almost certainly due to the laboratory environmental-control failure, and not to unique field weather conditions in collecting year 2003. On the other hand, this example shows that even short increase in temperature of meteorites can result in significant modifications of its characteristics. A possible explanation of the differences in the percent of evaporites present can be also an artifact of different people handling sample processing. Some of the parameters analyzed in the study (especially weathering class) can, be assigned slightly different values depending on decision of a technician taking care of the analysis. It is also not clear if two different people would assign the same meteorite to evaporite or non-evaporite group. However 88 comparison of the annual changes in abundance of evaporite-bearing meteorites (Table 7, Figure 10) and ANSMET staff (Table 9) does not show an obvious relationship. Additionally, process of training new staff members should exclude strong differences between way in which meteorites are categorized. On the other hand, AN SMET laboratory have experienced a major stuff change between 1994 and 1996 and in the same time there was a decrease in the average percentage of evaporite-bearing meteorites (Table 9 and Figure 10). This decrease can be either caused by the difference in environmental conditions (e. g., climatic trend) or curatorial processing. However it is not possible to test which of the hypothesis is supported with available data. 89 Table 11 Relation of weather in a given year to under- or over-abundance of evaporites. Weather data covers only years 1979-1999 (marked with gray). Evaporite data marked with with +/- (- less than average, + more than usually) only for years where a consistent trend (for all compositional groups) was identified. Year Winter J Summer Jan Eva 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 Relative importance of parameters At least three parameters influence the probability of evaporite occurrence on the Antarctic meteorites: Composition of meteorite (including its petrologic type), 90 location of meteorite recovery and year of collection. The relative importance of those three factors apparently varies from year to year and from location to location. Apparently, in some locations (e.g., DOM, LAP, MET, GRO, MIL) the influence of the local environment is so strong that all other factors have only secondary importance. In other meteorite-bearing ice fields, local geographical factors do not have such a strong impact, which allows other factors to dominate. Similarly, the influence of collection year varies not only in direction but also in strength; some locations (e.g., MET) cause systematic but slight decrease in number of evaporite-bearing meteorites, others (e. g., DOM) cause very strong decrease in percent of evaporitic meteorites (Table 6). Controlling for all three parameters (Table 8) reveals that in most cases, percentages are more similar within a given collection year than within the same location at different times. However, there are some exceptions; for example, in 2003, two fields were sampled that have especially strong influence, resulting in high over- (GRO — average percent of evaporite-bearing meteorites of 15.3%) and under- (LAP — 0.7%) abundance of evaporite-bearing meteorites. In 2003, exposure of meteorites to unusually high temperatures due to equipment failure caused increase in evaporite formation. Even though the entire collection was subjected to the freezer failure, only 1.2% of meteorites found in LAP field had evaporites, while in GRO field the same is true for 19.8%. On the other hand, some years have such a strong influence that the influence of geography (especially if visited fields do not have a very distinctive positive or negative influence) does not matter so much. For example, in 2004 0.5% H chondrites had evaporites on them — even though the average for the entire population is 5.3%. 91 Conclusions 1. Evaporite formation depends on compositional group, supporting the findings of Velbel (1988). a. C chondrites are class characterized by the highest percentage (~30%) of evaporite-bearing meteorites. b. Groups within the same class can have significantly different percent of evaporite-bearing meteorites, e.g., in L 'chondrites group 4.2% of meteorites have evaporites, while the same is true for only 1.7% of LL chondrites. 2. More evaporites are forming on meteorites of petrologic type 3 than on meteorites of higher petrologic types. This finding supports and expands the findings of Velbel (1988). 3. There is no apparent relation between evaporite formation and meteorite rustiness which contradicts the findings of Velbel (1988). 4. Some meteorite-bearing fields influence the frequency of evaporite-mineral formation on meteorites. The influence of location is apparently related to differences in environmental conditions, most probably microclimate or/and hydrologic conditions. There is no relation between abundance of evaporite- bearing meteorites and distance from the sea. This provides further support for the non-marine source of evaporites (e. g., Velbel et al. 1991). 92 5. Evaporite formation varies with year of collection. This may be related to: annual changes in climate, annual variation in other factor (e.g., hydrologic conditions) or be an artifact of sample categorization or curation. 6. The relative importance of different factors is hard to estimate. The importance of factors influencing evaporite formation varies between years and locations. However the influence of compositional group remains uniformly relatively strong. 93 Appendix 2 Name Type Porosity Error Source Cumberland Wilkison et al. 2003, Meteoritics &Pl. Falls AUB -0.3 2.4 Sc. 38(10)1533-1546. Tatahouine AUB 0 2 Flynn et al. 1999, Icarus 142, 97-105. Britt and Consolmagno, 2003, Tatahouine DIOG 2.5 Meteoritics and P1. Sc. 38(8) 1161-1180. Tatahouine DIOG 7 3 Flynn et al. 1999, Icarus 142, 97-105. Britt and Consolmagno, 2003, Juvinas EUCR 1.2 Meteoritics and P1. Sc. 38(8) 1161-1180. ALH76005 Britt and Consolmagno, 2003, EUCR 7.9 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Milibilillie EUCR 10 Meteoritics and P1. Sc. 38(8) 1161-1180. Pasamonte Britt and Consolmagno, 2003, EUCR 10.2 Meteoritics and P1. Sc. 38(8) 1161-1180. Millbillillie EUCR 11 l Flynn et al. 1999, Icarus 142, 97-105. Britt and Consolmagno, 2003, Sioux County EUCR 13.6 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Le Teilleul HOW 4.4 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Kapoeta HOW 5.1 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Nakhla SNC 4.2 Meteoritics and P1. Sc. 38(8) 1161-1180. EET79001 Britt and Consolmagno, 2003, SNC 4.9 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Zagami SNC 10.6 Meteoritics and P1. Sc. 38(8) 1161-1180. Murchison Britt and Consolmagno, 2003, CM 17.1 Meteoritics and P1. Sc. 38(8) 1161-1180. Nogoya CM 26.3 Britt and Consolmagno, 2003, 94 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Mighei CM 28.2 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Santa Cruz CM 30.3 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Cold Bokkeveld CM 12.9 Meteoritics and P1. Sc. 38(8) 1161-1180. Wilkison et al. 2003, Meteoritics &Pl. Murchison CM2 10 4.6 Sc. 38(10)1533-1546. Murchison Wilkison et al. 2003, Meteoritics &Pl. CM2 13.7 3.4 Sc. 38(10)1533-1546. Murchison CM2 l6 2 Flynn et al. 1999, Icarus 142, 97-105. Corrigan et al. 1997, Meteoritics &Pl. Murchison CM2 23 Sc. 32, 509-515 ‘ Murray CM2 29 2 Flynn et al. 1999, Icarus 142, 97-105. Lance Britt and Consolmagno, 2003, CO 15.2 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Omans co 17.4 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Warrenton CO 23.5 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Felix CO 22.9 Meteoritics and PI. Sc. 38(8) 1161-1180. Corrigan et a1. 1997, Meteoritics &Pl. lsna C03 4 Se. 32, 509-524 Corrigan et al. 1997, Meteoritics &Pl. Lance CO3 8.3 Sc. 32, 509-525 Kainsaz CO3 12 5 Flynn et al. 1999, Icarus 142, 97-105. Britt and Consolmagno, 2003, Vigarano CV 0.3 Meteoritics and P1. Sc. 38(8) 1161-1180. Grosnaja 'Britt and Consolmagno, 2003, CV 8.5 Meteoritics and P1. Sc. 38(8) 1161-1 180. Allende CV 18.5 Britt and Consolmagno, 2003, 95 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Axtel CV 20.7 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Kaba CV 20.9 Meteoritics and P1. Sc. 38(8) 1161-1180. Corrigan et a1. 1997, Meteoritics &P1. Vigarano3 CV3 1.9 Sc. 32, 509-523 Corrigan et al. 1997, Meteoritics &Pl. Leoville CV3 2 Sc. 32, 509-519 Corrigan et al. 1997, Meteoritics &P1. Vigaranol CV3 2 Sc. 32, 509-521 Efremova Corrigan et a1. 1997, Meteoritics &P1. CV3 7 Sc. 32, 509-518 Corrigan et a1. 1997, Meteoritics &Pl. Vigaran02 CV3 7 Sc. 32, 509-522 Bali Corrigan et al. 1997, Meteoritics &P1. CV3 10 Sc. 32, 509-517 Allende CV3 1 l 3 Flynn et al. 1999, Icarus 142, 97-105. Allende CV3 14 5 Flynn et al. 1999, Icarus 142, 97-105. Allende CV3 18 2 Flynn et al. 1999, Icarus 142, 97-105. Allende CV3 19 l Flynn et a1. 1999, Icarus 142, 97-105. Axtel CV3 19 0.5 Flynn et a1. 1999, Icarus 142, 97-105. Allende CV3 20 1 Flynn et a1. 1999, Icarus 142, 97-105. Corrigan et al. 1997, Meteoritics &Pl. Allende CV3 20 Sc. 32, 509-516 Allende CV3 21 0.5 Flynn et a1. 1999, Icarus 142, 97-105. Axtel CV3 21 2 Flynn et a1. 1999, Icarus 142, 97-105. Allende CV3 22 3 Flynn et al. 1999, Icarus 142, 97-105. Axtel CV3 22 0.6 Flynn et al. 1999, Icarus 142, 97-105. Mokoia Corrigan et a1. 1997, Meteoritics &P1. CV3 24 Se. 32, 509-520 96 Wilkison et a1. 2003, Meteoritics &P1. Allende CV32 12.8 7.9 Sc. 38(10)1533-1546. Britt and Consolmagno, 2003, lndarch E -0.5 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Hvittis E 2.7 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Abee E -4.1 Meteoritics and P1. Sc. 38(8) 1161-1180. Wilkison et al. 2003, Meteoritics &Pl. Hvittis E6 -0.5 6.3 Sc. 38(10)1533-1546. Estacado Britt and Consolmagno, 2003, H -1 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Pribram H O Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Gilgoin H 0.2 Meteoritics and P1. Sc. 38(8) 1161-1180. Tomhannock Britt and Consolmagno, 2003, Ck H 1 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Plainview H 1.6 Meteoritics and P1. Sc. 38(8) 1161-1180. Ferguson Britt and Consolmagno, 2003, Switch H 1.7 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Grady H 1.7 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Selma 1H 2.2 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Udipi H 3 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Erxleben H 3.5 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Orimattila H 3.5 Meteoritics and P1. Sc. 38(8) 1161-1180. Metsakyla Britt and Consolmagno, 2003, H 4 Meteoritics and P1. Sc. 38(8) 1161-1180. 97 Britt and Consolmagno, 2003, Wellrnan A 4.1 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Bur-Gheluai 4.4 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consohnagno, 2003, Pultusk 4.6 Meteoritics and P1. Sc. 38(8) 1161-1180. Bielokrynitschi Britt and Consolmagno, 2003, e 5 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Nammianthal 5 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Lancon 5.2 Meteoritics and P1. Sc. 38(8) 1161-1180. Mount Browne Britt and Consohnagno, 2003, 5.6 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Bath 6.8 Meteoritics and P1. Sc. 38(8) 1161-1180. Gladstone Britt and Consohnagno, 2003, 6.8 Meteoritics and PI. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Seres 6.8 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consohnagno, 2003, Cape Girardeau 7 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Nanjemoy 7.8 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Misshof 8.2 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consohnagno, 2003, Agen 8.5 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Y-74647 8.9 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Weston 9.2 Meteoritics and P1. Sc. 38(8) 1161-1180. Y-74156 Britt and Consolmagno, 2003, 9.2 Meteoritics and P1. Sc. 38(8) 1161-1180. 98 Britt and Consolmagno, 2003, Ochansk H 9.9 Meteoritics and P1. Sc. 38(8) 1161-1180. Corrigan et a1. 1997, Meteoritics &P1. Miyamoto H 10 Sc. 32, 509-530 Britt and Consolmagno, 2003, Forest City H 10.1 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Torino H 10.1 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Mooresfort H 11.4 Meteoritics and P1. Sc. 38(8) 1161-1180. Vernon County Britt and Consolmagno, 2003, H 11.8 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Trenzano H 12.6 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consohnagno, 2003, Menow H 15.7 Meteoritics and P1. Sc. 38(8) 1161-1180. Allegan Britt and Consolmagno, 2003, H 16.7 Meteoritics and P1. Sc. 38(8) 1161-1180. Corrigan et a1. 1997, Meteoritics &Pl. Willard H3 0 Sc. 32, 509-526 Wilkison et al. 2003, Meteoritics &Pl. Weston H4 -7.7 10.5 Sc. 38(10)1533-1546. Wilkison et al. 2003, Meteoritics &Pl. Ochansk H4 2.8 3.1 Sc. 38(10)1533-1546. Wilkison et a1. 2003, Meteoritics &P1. Kesen H4 9.4 2.2 Sc. 38(10)1533-1546. Wilkison et al. 2003, Meteoritics &P1. Menow H4 13.3 3 Sc. 38(10)1533-1546. Wilkison et a1. 2003, Meteoritics &Pl. Beaver Creek H4 15.3 2.2 Sc. 38(10)1533-1546. Corrigan et a1. 1997, Meteoritics &Pl. Forest Vale H4 18.1 Sc. 32, 509-527 Pultusk Wilkison et al. 2003, Meteoritics &Pl. H5 -4.6 5.7 Sc. 38(10)1533-1546. 99 Wilkison et al. 2003, Meteoritics &Pl. Pultusk H5 -3.8 6.4 Sc. 38(10)1533-1546. Miami H5 -2 2 Flynn et a1. 1999, Icarus 142, 97-105. Wilkison et al. 2003, Meteoritics &Pl. Stalldelen H5 -1.5 6.6 Sc. 38(10)1533-1546. Miami H5 -1 4 Flynn et a1. 1999, Icarus 142, 97-105. Wilkison et al. 2003, Meteoritics &P1. Forest City H5 0.6 4.2 Sc. 38(10)1533-1546. Wilkison et al. 2003, Meteoritics &Pl. Sindhri H5 3 5.6 Sc. 38(10)1533—1546. Pultusk Wilkison et al. 2003, Meteoritics &Pl. H5 5.3 3.8 Sc. 38(10)1533-1546. Juancheng H5 8 2 Flynn et al. 1999, Icarus 142, 97-105. Juancheng H5 8 2 Flynn et al. 1999, Icarus 142, 97-105. Leighton Wilkison et al. 2003, Meteoritics &Pl. H5 11.2 7.8 Sc. 38(10)1533-1546. Wilkison et al. 2003, Meteoritics &Pl. Allegan H5 12.9 15.1 Sc. 38(10)1533-1546. Corrigan et al. 1997, Meteoritics &P1. Zhovtnevyi H5 13 Sc. 32, 509-528 Wilkison et a1. 2003, Meteoritics &Pl. Barbotan H5 22 7.7 Sc. 38(10)1533-1546. Wilkison et a1. 2003, Meteoritics &Pl. Allegan H5 27.1 11.7 Sc. 38(10)1533-1546. Estacado H6 -3 2 Flynn et a1. 1999, Icarus 142, 97-105. Acfer 132 H6 4 7 Flynn et a1. 1999, Icarus 142, 97-105. Corrigan et a1. 1997, Meteoritics &Pl. Mt Browne H6 6.8 Sc. 32, 509-529 Ozona H6 8 1 Flynn et a1. 1999, Icarus 142, 97-105. Meuselbach Britt and Consolmagno, 2003, L -O.8 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Colby (WI) L O Meteoritics and P1. Sc. 38(8) 1161-1180. 100 Britt and Consolmagno, 2003, Sevrukovo 0.2 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Brandon 0.3 Meteoritics and P1. Sc. 38(8) 1161-1180. H. al Hamra Britt and Consolmagno, 2003, 071 0.3 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Futtehpur 0.5 Meteoritics and P1. Sc. 38(8) 1161-1180. Ness County Britt and Consolmagno, 2003, (1894) 0.7 Meteoritics and P1. Sc. 38(8) 1161-1180. Barratta Britt and Consolmagno, 2003, 0.9 Meteoritics and P1. Sc. 38(8) 1161-1180. H. a1 Hamra Britt and Consohnagno, 2003, 136 0.9 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consohnagno, 2003, ALH77230 1.1 Meteoritics and P1. Sc. 38(8) 1161-1180. McKinney Britt and Consolmagno, 2003, 1.3 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Farmington 1.6 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Segowlie 1.7 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Kermichel 1.8 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consohnagno, 2003, Chateau-Renard 1.9 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Fukutomi 2 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Bluff 2.3 Meteoritics and P1. Sc. 38(8) 1161-1180. Asco Britt and Consolmagno, 2003, 2.4 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Arapahoe 2.5 Meteoritics and P1. Sc. 38(8) 1161-1180. 101 St. Cgrus. -Ia- Britt and Consolmagno, 2003, Ch. 2.5 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Nagy-Borove 2.6 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, L'Aigle 2.7 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Dalgety Downs 2.8 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Stavropol 2.8 Meteoritics and P1. Sc. 38(8) 1161-1180. Mezo-Madaras Britt and Consolmagno, 2003, 2.9 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Minas Gerais 3.1 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Bruderheirn 3.2 Meteoritics and P1. Sc. 38(8) 1161-1180. Nerfi Britt and Consolmagno, 2003, 3.3 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consohnagno, 2003, ALH78105 3.9 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Kunashak 4 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Chandpur 4.2 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Sleeper Camp 4.3 Meteoritics and P1. Sc. 38(8) 1161-1180. Hermitage Britt and Consohnagno, 2003, Plains 4.7 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Berlanguillas 4.8 Meteoritics and P1. Sc. 38(8) 1161-1180. Mbale Britt and Consolmagno, 2003, 5.8 Meteoritics and PI. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, llafegh 11 6.1 Meteoritics and P1. Sc. 38(8) 1161-1180. 102 Britt and Consolmagno, 2003, Bachmut 6.2 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Durala 6.7 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, New Concord 6.7 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Alfianello 7.4 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, ALH77115 7.7 Meteoritics and P1. Sc. 38(8) 1161-1180. Cabezo de Britt and Consohnagno, 2003, Mayo 7.8 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consohnagno, 2003, META78003 7.8 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, ALH77231 8.5 Meteoritics and P1. Sc. 38(8) 1161-1180. Slobodka Britt and Consohnagno, 2003, 8.9 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consohnagno, 2003, Ausson 9.1 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Holbrook 9.1 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Homestead 9.1 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, M005 9.3 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Tennasilm 10 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Leedy 10.5 Meteoritics and P1. Sc. 38(8) 1161-1180. ALH78251 Britt and Consolmagno, 2003, 10.7 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, ALH78103 13.4 Meteoritics and P1. Sc. 38(8) 1161-1180. 103 Britt and Consolmagno, 2003, Saratov L 15.5 Meteoritics and P1. Sc. 38(8) 1161-1180. Mount Britt and Consolmagno, 2003, Tazerzait L 17.2 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, ALH77254 L 17.5 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, ALH76009 L 19.5 Meteoritics and P1. Sc. 38(8) 1161-1180. Corrigan et al. 1997, Meteoritics &Pl. Julesburg L3 5 Se. 32, 509-531 Krymka Corrigan et a1. 1997, Meteoritics &Pl. L3 6.7 Sc. 32, 509-532 Corrigan et a1. 1997, Meteoritics &Pl. McKinney L4 0 Sc. 32, 509-536 Corrigan et a1. 1997, Meteoritics &P1. Barrata L4 0.7 Sc. 32, 509-533 Bjurbole Wilkison et al. 2003, Meteoritics &Pl. L4 0.8 12.7 Sc. 38(10)1533-1546. Saratov L4 13 2 Flynn et a1. 1999, Icarus 142, 97-105. Corrigan et al. 1997, Meteoritics &Pl. Bjurbole L4 16.7 Sc. 32, 509-534 Corrigan et al. 1997, Meteoritics &P1. Saratov L4 18.2 Sc. 32, 509-535 Bjurbole L4 20 2 Flynn et a1. 1999, Icarus 142, 97-105. Bjurbole L4 23 1 Flynn et a1. 1999, Icarus 142, 97-105. Wilkison et a1. 2003, Meteoritics &Pl. Knyahinya L5 -4.7 8.9 Sc. 38(10)1533-1546. Corrigan et al. 1997, Meteoritics &Pl. Farmington L5 2.9 Sc. 32, 509-537 llafegh 11 L5 6 3 Flynn et al. 1999, Icarus 142, 97-105. Ausson L5 10 2 Flynn et al. 1999, Icarus 142, 97-105. Wilkison et a1. 2003, Meteoritics &Pl. Ergheo L5 14.4 5.1 Sc. 38(10)1533-1546. 104 Mt. Tazerzait L5 17 1 Flynn et a1. 1999, Icarus 142, 97-105. Wilkison et a1. 2003, Meteoritics &P1. Segowlie L6 -11.9 13.6 Sc. 38(10)1533-1546. Wilkison et al. 2003, Meteoritics &Pl. Holbrook L6 -9.5 15 Sc. 38(10)1533-1546. Wilkison et a1. 2003, Meteoritics &P1. Holbrook L6 -7.1 8.7 Sc. 38(10)1533-1546. Wilkison et al. 2003, Meteoritics &Pl. Fisher L6 -l.3 6.9 Sc. 38(10)1533-1546. Holbrook Wilkison et a1. 2003, Meteoritics &P1. L6 -1 .3 6.2 Sc. 38(10)1533-1546. Wilkison et al. 2003, Meteoritics &Pl. Blanket L6 -0.9 3.1 Sc. 38(10)1533-1546. Corrigan et al. 1997, Meteoritics &Pl. Kermichel L6 0.2 Sc. 32, 509-538 Holbrook Wilkison et al. 2003, Meteoritics &Pl. L6 0.6 4.9 Sc. 38(10)1533-1546. Wilkison et a1. 2003, Meteoritics &Pl. Holbrook L6 1.1 12.7 Sc. 38(10)1533-1546. Wilkison et al. 2003, Meteoritics &Pl. Holbrook L6 1.7 4.] Se. 38(10)1533-1546. Wilkison et a1. 2003, Meteoritics &P1. New Concord L6 2.8 3.5 Sc. 38(10)1533-1546. Wilkison et al. 2003, Meteoritics &Pl. Lissa L6 2.9 13.3 Sc. 38(10)1533-1546. Wilkison et a1. 2003, Meteoritics &Pl. Holbrook L6 3.7 3.4 Sc. 38(10)1533-1546. Wilkison et a1. 2003, Meteoritics &Pl. Holbrook L6 4.3 3.3 Sc. 38(10)1533-1546. Wilkison et al. 2003, Meteoritics &Pl. Vouille L6 5.7 4.9 Sc. 38(10)1533-1546. Holbrook Wilkison et a1. 2003, Meteoritics &P1. L6 6.2 4.2 Sc. 38(10)1533-1546. Mocs L6 6.9 2.3 Wilkison et a1. 2003, Meteoritics &P1. 105 Sc. 38(10)1533-1546. Wilkison et al. 2003, Meteoritics &Pl. Zavid L6 8.8 8.8 Sc. 38(10)1533-1546. Wilkison et al. 2003, Meteoritics &P1. Alfianello L6 1 1.9 7.9 Sc. 38(10)1533-1546. Hammadah a1 Hamra 136 L6 0.3 1 Flynn et al. 1999, Icarus 142, 97-105. Harnmadah a1 Hamra 71 L6 1 2 Flynn et al. 1999, Icarus 142, 97-105. Waltman L6 3 2 Flynn et a1. 1999, Icarus 142, 97-105. Sleeper Camp L6 4 4 Flynn et a1. 1999, Icarus 142, 97-105. Mbale L6 6 l Flynn et al. 1999, Icarus 142, 97-105. Holbrook L6 11 2 Flynn et a1. 1999, Icarus 142, 97-105. Holbrook L6 1 1 2 Flynn et al. 1999, Icarus 142, 97-105. Holbrook L6 11 2 Flynn et a1. 1999, Icarus 142, 97-105. Brandon L6-7 -3 4 Flynn et al. 1999, Icarus 142, 97-105. Brandon L6-7 3 2 Flynn et a1. 1999, Icarus 142, 97-105. Britt and Consolmagno, 2003, Richfield LL 1.6 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Dhurrnsala LL 3.9 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Knyahinya LL 4.3 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Richmond LL 6.3 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Parnallee LL 6.4 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Ottawa LL 7.1 Meteoritics and P1. Sc. 38(8) 1161-1180. Cynthiana Britt and Consolmagno, 2003, LL 8.9 Meteoritics and P1. Sc. 38(8) 1161-1180. Bjurbole LL 12.3 Britt and Consolmagno, 2003, 106 Meteoritics and P1. Sc. 38(8) 1161-1180. Britt and Consolmagno, 2003, Mangwendi LL 14.8 Meteoritics and P1. Sc. 38(8) 1161-1180. Wilkison et a1. 2003, Meteoritics &Pl. Soko-Banja LL4 6.8 9 Sc. 38(10)1533-1546. Wilkison et al. 2003, Meteoritics &Pl. Hamlet LL4 18.3 3.4 Sc. 38(10)1533-1546. Wilkison et a1. 2003, Meteoritics &Pl. Olivenza LL5 -2.5 11.3 Sc. 38(10)1533-1546. Tuxtuac Wilkison et a1. 2003, Meteoritics &Pl. LL5 13.3 5.9 Sc. 38(10)1533-1546. Wilkison et al. 2003, Meteoritics &Pl. Dhunnsala LL6 4 2.1 Sc. 38(10)1533-1546. Wilkison et a1. 2003, Meteoritics &Pl. Dhunnsala LL6 5.2 8.9 Sc. 38(10)1533-1546. 107 Appendix 3 Meteorites are usually named based on the locality (town or village) or the geographic feature nearest to the point of recovery (Hutchison 2004). Parts of the same fall are given the same name (but, for finds only, if necessary different numbers are assigned). Sometimes two meteorites of unknown relationship are found in close proximity to each other and are distinguished using a parenthesized lower case letter. Meteorites found in deserts are named using slightly different rules because of so many of them were found in close proximity to each other, and the distinguishable geographic features are scare. For example, name of Antarctic meteorite (e.g., LEW 85327) consists of three upper case letters that correspond to the meteorite-bearing ice field where the specimen was found (e.g., LEW stands for Lewis Cliff), and five digit number. The first two numbers correspond to the year of the field season in which the meteorite was found (e.g., field season 1985-1986). Three other numbers refer to the order in which the specimen was found. Official names of new Antarctic meteorites are published in the Antarctic Meteorite Newsletter. 108 0 Mai 1.3.. _.._.__.._.._-..._-L-L-:-z-0 0 0 s r z 0 0 r r r r r r r r r . r . . r . : Appendix 4 Weathering category Main meteorite . Meteorite from the . . total Ev. % grouping classrficatron A A/B B BIC c ALHA 77081 Acap 3 0 0.0% 2 1 ALHA 81187 Acap 2 0 0.0% 1 1 MET 01 195 Acap 5 0 0.0% 1 4 GRA 06128 “TQM“? 2 1 50.0% ALH 83009 Aub 20 1 5.0% 14 6 LAP 02 233 Aub 4 0 0.0% 3 1 LEW 87007 Aub 10 0 0.0% 5 5 EET 99402 Brach 2 0 0.0% 2 ALH 85005 C2 8 1 12.5% 3 2 3 EET 83226 C2 2 0 0.0% 2 EET 90047 C2 2 0 0.0% 2 EET 92005 C2 5 0 0.0% 1 3 1 EET 96005 CZ 15 7 46.7% 1 1 13 LEW 85306 C2 5 2 40.0% 2 1 2 LEW 86004 C2 5 3 60.0% 3 2 LEW 88001 C2 3 2 66.7% 1 1 1 LON 94101 C2 2 2 100.0% 1 1 MAC 87300 CZ 2 0 0.0% 2 MCY 92500 C2 2 1 50.0% 1 1 PCA 91084 CZ 3 2 66.7% 2 1 QUE 93004 CZ 5 2 40.0% 3 Z QUE 93005 CZ Z 1 50.0% 2 QUE 94220 CZ Z 2 100.0% 2 RKP 92400 CZ 3 1 33.3% 1 Z WIS 91600 CZ 2 1 50.0% 2 PCA 91328 CH 3 0 0.0% 1 1 1 QUE 94411 CH 3 0 0.0% 2 1 LAP 04 757 Chondrite u.g. 2 0 0.0% 2 ALH 82135 CK4 3 1 33.3% 3 LEW 87214 CK4 2 0 0.0% 2 QUE 99675 CK4 5 5 100.0% 5 EET 87507 CK5 48 34 70.8% 2 11 35 QUE 99680 CK5 Z 2 100.0% 2 LAR 04 317 CK6 2 0 0.0% 1 1 MET 01070 CM1 3 1 33.3% 3 MCY 05 231 CM1-Z 2 0 0.0% 2 ALH 83100 CM2 Z1 14 66.7% 15 Z 3 1 ALHA 81002 CM2 14 4 28.6% 11 3 GRA 98005 CM2 2 2 100.0% 2 LEW 87001 CM2 9 0 0.0% 3 6 110 MET 00431 CM2 2 1 50.0% 1 1 MET 00431 CM2 4 4 100.0% 4 MET 01071 CM2 4 0 0.0% 4 MET 01076 CM2 2 0 0.0% 1 1 QUE 97077 CM2 2 0 0.0% 1 1 QUE 99342 CM2 2 1 50.0% 2 LAP 02 239 CM2 2 0 0.0% 2 LAP 02 269 CM2 4 0 0.0% 2 2 LAP 02 336 CM2 2 0 0.0% 2 LAP 03 718 CM2 2 1 50.0% 2 LAP 03 786 CM2 2 0 0.0% 1 1 LAP 031043 CM2 5 0 0.0% 1 4 LAP 04 527 CM2 7 0 0.0% 1 3 2 MAC 02 779 CM2 2 0 0.0% 1 MCY 05 229 CM2 5 0 0.0% 5 MIL 05 112 CM2 2 1 50.0% 1 1 PCA 02 011 CM2 3 0 0.0% 1 2 ALH 77003 C03 3 1 33.3% 2 1 ALH 82101 C03 2 0 0.0% 1 MIL 03 377 C03 5 1 20.0% 2 1 1 MET 00 694 COB 2 0 0.0% 1 EET 87711 CR2 50 4 8.0% 1 1 36 3 ALH 84028 CV3 2 2 100.0% 1 1 MET 00429 CV3 2 0 0.0% 2 MET 01074 CV3 2 0 0.0% 2 QUE 93429 CV3 4 2 50.0% 1 1 2 QUE 94366 CV3 2 1 50.0% 1 1 ALHA 81003 CV3 2 0 0.0% 1 1 LAP 02 206 CV3 2 0 0.0% 2 LAP 03 979 BIG 2 0 0.0% 2 LAP 91 900 BID 8 0 0.0% 8 PCA 02 008 010 2 0 0.0% 1 1 QUE 99 050 010 2 0 0.0% 1 1 LEW 87057 E3 6 1 16.7% 1 4 QUE 93513 E4 2 0 0.0% 2 ALHA 77156 EH3 2 0 0.0% 2 ALHA 81189 EH3 9 O 0.0% 1 3 1 4 EET 83307 EH3 3 1 33.3% 1 2 PCA 82518 EH3 21 4 19.0% 1 9 7 4 EET 96135 EH4-5 7 1 14.3% 1 2 2 2 EET 90299 EL3 2 0 0.0% 2 MAC 02 837 EL3 2 0 0.0% 2 MAC 88136 EL3 3 0 0.0% 1 2 QUE 93351 EL3 3 0 0.0% 3 ALHA 81021 EL6 3 1 33.3% 1 1 1 LEW 88135 EL6 2 1 50.0% 1 1 ALHA 76005 EUC 14 0 0.0% 11 3 EET 92025 EUC 2 0 0.0% 2 111 EETA 79004 EUC 9 0 0.0% 9 EETA 79005 EUC 3 0 0.0% 2 EETA 79006 EUC 2 1 50.0% 1 GRA 98006 EUC 8 0 0.0% 2 1 GRA 98019 EUC 13 0 0.0% 6 5 LAP 031190 EUC 2 0 0.0% LEW 85300 EUC 4 0 0.0% 1 MET 01081 EUC 2 0 0.0% PCA 82502 EUC 3 2 66.7% 2 PCA 91078 EUC 2 0 0.0% 1 PCA 91079 EUC 3 1 33.3% 2 QUE 94204 EUC 8 0 0.0% 1 7 LAP 02 240 H 3 0 0.0% 3 LAP 031173 H 3 0 0.0% 1 2 BTN 00301 H33 3 0 0.0% 3 GRA 98023 H38 4 0 0.0% 1 3 EET 87726 H39 3 0 0.0% 3 ALHA 77004 H4 12 2 16.7% 12 ALHA 77009 H4 2 0 0.0% 1 1 ALHA 78193 H4 3 0 0.0% 1 2 ALHA 80106 H4 4 0 0.0% 2 1 1 ALHA 81041 H4 11 0 0.0% 5 6 EET 96031 H4 5 0 0.0% 3 2 LEW 88019 H4 2 1 50.0% 1 1 MAC 88145 H4 2 0 0.0% 1 1 QUE 93081 H4 3 0 0.0% 3 RKPA 80237 H4 2 0 0.0% 2 ALHA 77014 H5 2 0 0.0% 1 ALHA 77021 H5 9 0 0.0% 5 4 ALHA 77118 H5 3 0 0.0% 3 ALHA 78209 H5 5 0 0.0% 2 3 ALHA 79031 H5 2 0 0.0% 2 ALHA 80111 H5 5 0 0.0% 5 LEW 85316 H5 3 0 0.0% 3 MAC 88203 H5 2 0 0.0% 2 PKPA 80220 H5 2 0 0.0% 1 1 QUE 93029 H5 4 0 0.0% 3 RKPA 80217 H5 2 0 0.0% 2 RKPA 80250 H5 2 0 0.0% 1 1 TIL 82412 H5 2 0 0.0% 2 TIL 82414 H5 2 0 0.0% 1 LAP 02 231 H5 2 0 0.0% 2 LAP 04 672 H5 2 0 0.0% 2 ALH 85030 H6 3 0 0.0% 2 1 ALHA 77144 H6 2 0 0.0% 1 1 ALHA 77271 H6 2 O 0.0% 2 ALHA 78211 H6 5 0 0.0% 3 2 ALHA 80122 H6 3 0 0.0% 2 112 ALHA 81035 H6 4 0 0.0% 2 2 EET 82610 H6 2 0 0.0% 2 MAC 88130 H6 4 0 0.0% 4 MBRA 76001 H6 2 0 0.0% 2 PCA 82526 H6 2 0 0.0% 1 RKPA 80203 H6 13 0 0.0% 1 2 1 EET 87503 HOW 7 0 0.0% 4 1 EET 92014 HOW 2 0 0.0% 2 EET 96003 HOW 2 0 0.0% EET 99400 HOW 2 O 0.0% 1 1 GRO 95534 HOW 5 0 0.0% 3 LEW 85441 HOW 2 0 0.0% 2 LEW 87005 HOW 3 0 0.0% MET 96500 HOW 3 0 0.0% 2 1 MIL 05 062 HOW 2 0 0.0% 2 PCA 02 009 HOW 9 0 0.0% 1 7 1 PRA 04 401 HOW 2 1 50.0% 1 1 QUE 99033 HOW 2 0 0.0% 2 ALHA 76002 IA 5 0 0.0% EET 87504 IAB 4 0 0.0% 1 2 ALHA 78100 IIA 2 0 0.0% DRPA 78001 IIAB 11 3 27.3% 2 MET 00400 IIIAB 23 O 0.0% 23 LEW 86211 Iron 2 0 0.0% RBT 04 162 Iron 2 0 0.0% LAP 03 822 L 2 0 0.0% 2 MIL 05 029 L 3 1 33.3% 1 1 1 ALHA 77216 L3 4 0 0.0% 1 3 ALHA 78046 L3 2 O 0.0% 1 GRO 03 015 L3 2 1 50.0% 2 GRO 95502 L3 11 0 0.0% 5 5 MAC 02 467 L3 3 0 0.0% 2 1 RKPA 80256 L3.0/3.9 2 0 0.0% 2 LEW 85396 L3.2/3.5 3 1 33.3% 2 1 LEW 86307 L3.3/3.5 2 0 0.0% 2 EET 90080 L34 3 1 33.3% 3 LEW 85434 L34 4 0 0.0% 4 LEW 86127 L3.4 10 1 10.0% 3 2 4 LEW 88254 L34 3 O 0.0% 1 2 EET 83274 L36 2 0 0.0% 2 EET 90909 L36 2 0 0.0% 1 1 MET 00 489 L36 5 0 0.0% 1 4 ALHA 77011 L3.8 78 2 2.6% 2 13 21 36 EET 90745 L4 3 0 0.0% 3 MAC 87302 L4 2 O 0.0% 2 RKPA 80216 L4 2 0 0.0% 1 1 TIL 91700 L4 14 0 0.0% 9 4 1 ALHA 81018 L5 2 0 0.0% 2 113 GRO 85214 L5 4 0 0.0% 3 1 PCA 82504 L5 2 0 0.0% 1 1 PCA 91011 L5 3 2 66.7% 1 2 QUE 90201 L5 123 4 3.3% 1 54 59 9 RKPA 80209 L5 3 0 0.0% 1 2 ALHA 77001 L6 5 1 20.0% 1 1 3 ALHA 77272 L6 4 1 25.0% 3 1 ALHA 78043 L6 2 0 0.0% 1 1 ALHA 78103 L6 2 0 0.0% 2 ALHA 80101 L6 18 1 5.6% 1 15 2 ALHA 81027 L6 3 0 0.0% 1 2 EET 82605 L6 2 0 0.0% 2 EET 83317 L6 4 0 0.0% 4 EET90053 L6 678 14 2.1% 2 163 347 123 43 LAP 91901 L6 2 0 0.0% 2 PCA 91009 L6 14 1 7.1% 6 7 1 PCA 91029 L6 28 0 0.0% 28 PCA 91503 L6 7 0 0.0% 1 4 2 QUE 94202 L6 23 0 0.0% 15 4 4 RKPA 78001 L6 10 1 10.0% 1 6 3 RKPA 78002 L6 2 2 100.0% 2 ALHA 79003 LL3 2 0 0.0% 2 ALHA 76004 LL3.2/3.4 2 0 0.0% 1 1 EET 96109 LL3.4 2 0 0.0% 2 DAV 92302 LL3.6 2 0 0.0% 1 1 RKP 92413 LL3.7 2 1 50.0% 2 DOM 85505 LL5 2 O 0.0% 1 1 ALH 78153 LL6 3 0 0.0% 1 1 1 EET 90031 LL6 2 0 0.0% 1 1 EET 92017 LL6 5 0 0.0% 2 2 1 LEW 88564 LL6 3 0 0.0% 2 1 RKPA 80222 LL6 3 0 0.0% 2 1 EET 92012 LL7 3 0 0.0% 3 LAP 02 205 LUN 6 0 0.0% 2 1 3 MAC 88104 LUN 2 2 100.0% 2 QUE 93069 LUN 2 O 0.0% 2 ALHA 77219 Meso 3 0 0.0% 1 2 EET 87500 M050 3 0 0.0% 2 1 QUE 86900 Meso 11 2 18.2% 4 5 2 RKPA 79015 M630 5 0 0.0% 1 1 3 PCA 91004 PAL 3 0 0.0% 3 LAP 02 238 R 2 0 0.0% 2 LAP 03 639 R 7 1 14.3% 2 4 1 LAP 031135 R 2 0 0.0% 1 1 PCA 91002 R 2 1 50.0% 1 1 PRE 95410 R 3 0 0.0% 3 RBT 04 261 SHE 2 0 0.0% 2 ALH 82106 URE 3 0 0.0% 3 114 ALHA 78019 URE 2 0 0.0% 2 CMS 04 044 URE 2 1 50.0% EET 87511 URE 3 0 0.0% 1 1 EET 96293 URE 3 0 0.0% 3 EET 96322 URE 2 0 0.0% 1 1 LAP 03 721 URE 3 0 0.0% 2 1 LEW 85440 URE 4 1 25.0% 3 1 QUE 93336 URE 3 0 0.0% 2 1 115 REFERENCES Al—Kathiri A., Hofrnann B.A., Jull A.J.T., Gnos E., 2005, Weathering of meteorites from Oman: Correlation of chemical/mineralogical weathering proxies with 14C terrestrial ages and the influence of soil chemistry. 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Meteoritics & Planetary Science 38(10), 1423-1548. 119 Zolensky M., Barrett R., Browning L., 1993, Mineralogy and composition of matrix and chondrule rims in carbonaceous chondrites. Geochimica et Cosmochimica Acta 5 7(1 3), 3123-3148. 120 CONCLUSIONS Previous research showed that the way in which meteorites weather depends on the meteorite compositional class. Because of this all previous studies of meteorite weathering were conducted by organizing data and observations assuming a dominant influence of this parameter. This study suggests that more variables should be taken into account. The geographic location of meteorite-bearing ice fields influences the frequency of evaporite formation in the ANSMET population of Antarctic meteorites. This shows that the Antarctic environment varies significantly among meteorite bearing fields, and that environment has to be taken into account when analyzing a single specimen (especially for some fields that seem to have a particularly strong influence on the development of evaporites). Large disparities between amounts of evaporite-bearing meteorites between different collection years suggest that significant amounts of weathering take place in very short time scales in keeping with previous finding (e.g., Jull et a1. 1989). Based on the AN SMET database, only about 5% of meteorites have evaporites on their surface. However, EET79004 that is not marked with “e” and contains considerable amounts of evaporites is present within the fusion crust vesicles and cracks of the 3mm outermost layer of the meteorite. This shows that evaporites are probably more widespread among Antarctic meteorites than previously assumed. 121 NIVERSITY LIBRARIES I 1111 m l 303 8328 "IIIIIIIIIII