A METHOD OF DIFFERENTIATTNG CARBONATE AND SILICATE FACIES OF THE NEGAUNEE IRON FORMATION BY SPECTROCHEMl-CAL ANALYSIS Thesis for the Degree of M. S. MICHTGAN STATE UNIVERSITY THOMAS D. WAGGONER 1967 LIBR/‘RY “‘ _ Michigan State i Univc: it)! {A ABSTRACT A METHOD OF DIFFERENTIAIING CARBONAIE AND SILICATE EACIES OF THE NEGAUNEE IRON FORMATION BY SPECTROCHEMICAL ANALYSIS I by Thomas D. Waggoner A spectrochemical method of differentiating a predominantly magnetite-chert-carbonate facies from a magnetite-chert-silicate facies has been developed and successfully applied to the primary magnetite-chert deposits of the Negaunee ironpformation. Interpretation of the spectrochemical data depends on a point distribution representing the elements: magnesium, manganese, alu- 'minum and iron. manganese ions substitute readily for cations in the complex iron carbonates and only to a very minor extent in the iron silicates; the amount of manganese present can be used to approximate the quantity of carbonate present. A plot of manganese values versus magnesium values shows a trend of both elements which indicate higher concentrations of carbonate and possibly silicate. To evaluate the amount of silicate present when both Mg and Mn values are high, a plot of magnesium values versus aluminum is considered. Aluminum occurs exclusively in the iron silicates which are pro- ducts of a similar chemical environment to those of carbonates and mag- netite. The comparative analysis becomes vague when detrital feldspar contributes to the aluminum values. A plot of magnesium against iron may indicate the abundance of magnetite, but caution must be used in considering the type plot shown due to the extensive iron values present in all the minerals except chert. Silica cannot be used to correlate facies types due to its errat- ic occurance which is governed by stability fields not sufficiently clear at the time of the present study. Phosphorous has little value in making an accurate correlation due to its dependence on a pH condition and not on the other elements or their stability fields. Spectrochemical technique can be utilized in differentiating soft carbonate ores from the harder silicate types in iron ore blending and beneficiation. A METHOD OF DIFFERENTIATING CARBONATE AND SILICATE EACIES OF THE NEGAUNEE IRON FORMATION BY SPECTROCHEMICAL ANALYSIS by Thomas D. Waggoner A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Geology 1967 ACKNOWLEDGMENTS The author wishes to thank Dr. H.B. Stonehouse and Dr. R. Ehrlich for their guidance on.laboratory procedure and manu- script preparation. He also wishes to express gratitude to Dr. J.W. Trow and the late Dr. J. Zinn who provided.helpful suggest- ions on research. Acknowledgment is given to G. Anderson, J. Ortman and Tsu- Ming Han of the Cleveland-Cliffs Iron Company and J. Avery and B. Kangus of the Jones and Laughlin Steel Corporation for pro- viding core samples from their prOperties along with valuable information of the facies studied. The author is indebted to his wife, Jean, for final pre- paration of the manuscript and to Lembit Liivoja for preparation of the maps and figures. - 11 - CONTENTS AMWWMMSOOOOOOOOOOODOOOOOOOOOOOOO.00.0.0.0... LIST OF MP8 AND FIGURESOOOOOOOOOODOOQOOOCOOOOOIOO0.. LIST OF APENDICESOOOOOOOOOOOOOOO0.000000...0.0.0.... I. INTRODUCTION II. III. IV. V. VII. General.................................. LocationOOOOOOOCOOOOOOOOOOOOOOQOOOOO.'0CO GeOIOSYOOOQOOOOOOOOOOOOOOOOOO00000000..O. MineralogyOOOQ.OOOOOOOOOOCOOOO0.0.000...O ENVIRONMENTAL CONSIDERATIONS EntrOPYOOOOCOO.OOOOOOOOOOOOIOOOOOOOOOOOO. SilicaOOOOOOOOOOOOOOOOOOOOOOCOOOO00...... Magnetite-carbonate-silicates............ PhOBphOtOUB and aluminum................. Physical environment..................... LABORATORY PROCEDURE Sample preparation....................... Internal standard........................ SPGCtrOSraph setting‘oooooococoocoooocoo. Standardization......o...................g Denaitometercoooocooao0.0000000000000000. PhOtO developing.............o........... ImmPRETATIONOOOOOOOOOOOOOOOOOOOOOOOCOOO... CONCLUSIONSOOOOOOOOOOOOOOOOOOOOOOOOODOCOOOOO REPERENCESOOOOOOOOOOOCOOOOOOOOOOOOOO00...... APPENDICESOCOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO - iii - Page ii iv ONNH 15 15 19 19 24 24 25 25 26 26 27 32 34 38 C ' . . . . . . . a Q \ . a u . ‘ c. 0 ~ I i . 1 It .0 - , _ ...-... . a ‘0. a' a ‘ . . --‘-- ' n I - I u . 4- ‘ f .a‘ D. b.‘ o .. l ; l .I' ." n, . u , u a: a 0. I. . to . t '- ‘h"- .- .. CI‘ 0 LIST OF MAPS Maps Page 1 Location........................... 3 2 P1811GOOIOSY....................... 5 LIST OF FIGURES Figures Page I Manganese versus L.0.I............. 18 II Manganese versus Magnesium......... 28 III Magnesium versus Aluminum.......... 30 IV’Magnesium versus Iron.............. 31 - 1v- LIST OF APPENDICES APPENDIX A............................... Log of samples A - 1 through A - 23. Log of samples B - 1 through B - 17. Log of samples C - 1 through G - 15. APPENDIX B............................... Densitometer Graph Evaluation APPENDIX C............................... Loss on Ignition Procedure Page 38 39 41 43 55 INTRODUCTION Magnetic ores of the Marquette Range can be divided into two gen- eral types: magnetite-chert-carbonate and magnetite-chart silicate. Nomenclature may be misleading when discussing carbonate or silicate facies and in interpreting the spectrochemical data. Both the car- bonate and silicate minerals are minor constituents of the predomin- ently magnetite-chert rock and only the quantity relationship of one to the other defines the facies type. The name'silicate' ore is based on the relative abundance of iron silicate minerals, but in actuality the silicate facies usually contain almost twice as much car- bonate as does the defined carbonate facies. Thus the carbonate facies contains little or no iron silicate minerals while the silicate facies contains from one to five percent iron silicate minerals but may con- tain abundant carbonate. In a discussion of element distribution in the iron-formation, the mineralogical composition and the general environment under which the mineral assemblage was deposited are considered. Since the min- eralogical composition dictates a definite element distribution, an attempt will be made through the use of spectrochemical analysis to differentiate between the two major ore types. The advantage to the proposed method is one of speed and reproducibility. This can be achieved once the procedure is standardized. GEOLOGY The Negaunee iron-formation is part of a sequence of Animikan (Huronian) meta-sediments which form a western pitching synclinor- ium. The iron-formation is middle Animikan in age and is underlain by the Siamo slates and graywacke. Further discussion of the com; plete stratigraphy and lithologies are covered in work done by Van Hise (1897), Twenhofel (1952) and Hase (1957). The iron formation has a gross composition of chert, magnetite, carbonate and silicate and can be divided into two distinct zones (Adler, 1935). The upper secondarily oxidized portion reflects main- ly a chert-hematite-magnetite sedimentary facies. The lower portion, where unoxidired, reflects mainly a chert-magnetite-csrbonste-sil- icate sedimentary facies which exhibits large individual quantity variations for any random portion. Abundant magnetite-carbonate-silicate facies.occur in the east- ern end of the Marquette geosyncline in the lower portion. Second- ary oxidation is confined to fracture patterns adjacent to dikes. The geosyncline has undergone various stages of metamorphism. The western portion of the geosyncline has been highly metamorphosed (staurolite.facies) perhaps causing ion migration during the formation of specularite, grunerite and stilpnomelane. The eastern portion shows the lowest metamorphic rank (greenschist facies--quartz-a1bite- muscovite-chlorite subfacies). It is logical to assume that the least ion migration has occurred in the eastern portion and that the primary element concentration has not been notably disturbed. - 2 - R. 27 W. l R.26 W. 'r. 47 NJ 1.4s u. I Z“ .7.» 7-; ’ 52/, .2 /'7..—-+--' Is (I) —. Q, w e /"3 5/ / ' I9 I x" Lii‘er:~g-IL_/‘ / I /EMPl5E ‘ "" ’"J g" "MINE I’ 1 ”W“ ' "’\ III? , i r 9a» C301. beam 28 ,/ 27 I” I a “"7 W . _. , \/. 0' I 1’ (I LK. N/F'} ‘~\ SUPERIOR IRQM 3m 32 33 34 {50“ “Mng fa m ,- (a r milk- ” W 0° .1 figs/A \I Q~ I' I ,BARAGA J LOCATION PLAN MAP I CC. r OF , I I L J . SAM PLED AREA I “AROUETTE 00- MARQUETTE COUNTY, MICHIGAN IRON co. L--___‘ I SCALE I": I MILE l Selection of the drill locations for core sampling was based on three factors: the presence of carbonate-silicate facies, the extent of alteration-oxidation and the degree of metamorphism. Samples of core were taken from three drill holes which penetrated the lower portion of the Negsunse ironpformation. The drill holes are located in section 7, 8, and 18, T. 47 N, R. 26 w, Marquette County, Michigan (page S). The drill angle, depth, lithologies and corresponding specimen number are given in appendix A. -——-—-— -——- —...-" -- I GEOLOGY PLAN MAP OF SAMPLED AREA INSET PREVIOUS PAGE SCALE I": 500 FT. 848 0 SEC. 7 a .1 SEC. Ia __ __ ._.. __ _. __ :1 -——~ 2 #— LEGEND -— FAULTS DIORITE [2 IRON FORM. E . SIAMO SLATE MINERALOGY The portion of the Negaunee iron-formation studied contains the following minerals in the decreasing order of their abundance: 'chert, magnetite, iron carbonate, minnesotaite, hematite, stilpnomelsne, chlor- ite, biotite, elastic quartz and feldspar, apatite, glaucOphane and tourmaline. Almost 98 per cent of the formation consists of chert, magi netite, hematite, carbonate and iron silicates in various proportions. Detrital zones are prevalent near the top of the unoxidised lower por- tion of the formation. Quartz, feldspar and biotite are usually restric- ted to these sediments and are not important in the consideration of the facies studied. Minor grephite and pyrite occur in certain contacts be- tween the clastic and chemical facies. Their occurrence is minor and need not be considered here. ‘th E (8102) In the present study the term chert refers to a fine grained chemically precipitated form of quartz. It is associated with magnetite, iron carbonate and iron silicates in various prOportions. In thin section (Plate I) it appears as white, yellow or bluish-white grains; the abnormal color is due to the thick sections. Magnetite (Fe304) The mineral form is commonly euhedral (octahedron) and the size varies from a few microns to a few millimeters (Plate 111). Identification is made from its crystalline shepe and opacity. Generally, the magnetite is associated with chert and to a minor extent occurs in the chert-carbonate and/or chert-silicate laminae. Most of the magnetite is believed to be recrystallised which is indicated by widempread replacement .6- ,0 ', tI‘.'l PLATE I Sample B-la, cross nicols. Secondary quartz band showing the outlines of chert and primary clastic quartz (white and blue). The green material is chlorite. The black material consists of magnetite and hematite. Three second exposure with Ectachrome X. All pictures were taken with an Exacta Single Reflex camera specifically adapted to a Leitz-Wetzlar Polarizing Microscope. All shots were made at 200x magnification. Photo- graphs were taken with Kodak products. o 0.9 f ‘ 4%" PLATE II Sample A-4, plane polarized light. Gradation of magnetite facies into chert- carbonate-silicate facies. Two second ex- posure with Panatomic x. of chart by magnetite. The quantity of magnetite varies between 20 and 40 per cent by weight in any random sample. Hematite (PegOa) Occasional hematite was observed along bedding planes and fractures. In shallow portions of hole B, hematite occurs as martite, a pseudomorph after magnetite. In areas of secondary oxidation fine flakes and red stains indicate ground water activity. In these areas the carbonate and silicates have been oxidized and elements have been transported in and out. Under such conditions the facies analysis is not representative of primary conditions, and core samples containing traces of oxidation were not used. $523 Carbonate (PeMgMnCa)C03 Identification was based on optical prOperties and in some cases the obvious rhombohedral form. The color varies from.clear to light green to slightly brownish. The mineral is usually observed in distinct laminae or associated with chert and minor silicates. The actual chemical composition is variable (Pe.54-.75 M8.25-.20M’n.10-.03Cs.Ol)CO3 (Clarke); other variations are always pos- sible. Recent work on carbonate iron-formations indicate distinct zones of snkerite and siderite with minor cation variation within a given car- bonate (Trendsl, 1966). Stilpnomelane (OR,)4(KNaCs)0-1(FeMgAl)7.g(818023-24)'4820 The min- eral was only tentatively identified due to the fact that it closely re- sembles biotite. Very few occurrences were noted in the area studied. Minnesotaite (OH)22(FGH8)22(3130AIF°)2°74 The predominate iron sil- icate is minnesotaite. In thin section it is not pleochroic but does show a distinct green color. Nearly parallel extinction and strong bire- fringence help distinguish it from.chlorite which occurs in the elastic zones. Structurally it appears as radiating needles intergrown with the chert and carbonate (Plates VIaud VI). -9. PLATE III Sample A-21, plane polarized light. Secondary magnetite octahedra in a ground mass of chert-carbonate-silicate. Two sec- ond exposure with Panatomic X. - 10 - PLATE IV Sample B-lO, plane polarized light. Secondary (FeMgMnCa)C03 rhombohedra in a chert-carbonate-silicate band. Note only minor magnetite is found in the band but that it predominates both stratigraphically above and below. - 11 - PLATE V Sample A-19, plane polarized light. Minnesotaite has a slightly green color, which is intensified by the green color im- parted to the photograph by the blue light filter used on the microscOpe. Radiating needles and negative sign help distinguish the mineral from similar iron silicates. Two second exposure with Ectachrome X. - 12 - PLATE VI Sample A-19, cross nicols. The blue, white and yellow grains are chert while the dark portions are a combination of chert- silicate-carbonate which have undergone sur- face oxidation. Pour second exposure with Ectschrome x. - 13 - ENVIRONMENTAL CONSIDERATIONS To understand and interpret the element distribution, a discussion of the geochemistry and the general environment is presented. Phase equilibritsn conditions for recoa, M3603, MnCO3 and 39304 are discussed in works by Huber (1953, 1958) and Carrels (1952, 1960). Mo quantitative energy values are available for the iron silicates, but due to their natural association with carbonates, it is assured that they are governed by similar types of thermodynamic considerations. Under the same stability field of deposition, magnetite will form in preference to iron carbonates as long as sufficient oxygen is avail- able. The explanation involves the lower and more stable energy state achieved by magnetite with the use of less energy (heat) under any given Eh condition. Although hematitic portions of the formation have been avoided in the analysis procedure, it is helpful to discuss oxidation as it relates to the rate of alteration of the minerals in the carbonate-silicate facies. Entropy (As-cal/deg. mole) can be defined as the energy state of a system which is determined by the division of the absorbed energy by the abso- lute temperature of formation. 92-. A s - T The following are entrapy values at 25°C.: PeCO3 . . . . 22.2 Mg003 . . . . 15.1 MnCOg s s s s 2005 . complex iron silicate L35 -14... Oxygenated circulating ground water oxidizes carbonates and silicates to hematite at a faster rate than magnetite is altered to martite. The en- tropy levels of the silicates and carbonates are lower so that energy input at any given temperature will almost always affect the carbonates and silicates first. Silica precipitation is also covered by thermodynamic conditions, but they have no direct correlative value in the present study. Work done on the equilibrium conditions has given conflicting and inconclu- sive results. Krauskoff (1956) maintains that pn has absolutely no ef- fect on silica precipitation in true solution from a pH of 0 to 9. How- ever, Moore and Maynard (1929) indicate silica, carried as a colloid, is precipitated when transporting acidic solutions are neutralized in the presence of a carbonate. Krauskoff mentioned a precipitate of uncertain composition formed when a normal silica solution approached a p11 of 7 from an acid solution. Huber and Garrels (1953) have shown silica is transported currently by fresh water streams with pH values of 5 to 7 and an 8h of .25 to .30. The water has a high (:02 content which would generally increase for cold- er streams. The chert and silicate all contribute to the intensity of the silica spectrum line. The results show that silica is of little value in facies differentiation. The quantitative values for the carbonate cations have been pre- viously stated and from them it is noted that iron and magnesium predom- inate. The quantity of iron present suggests that the principle carbon- ate is siderite (Peco3) with minor magnesite (Mgc03) or an isomorphous series of the two near the iron rich end (Pe.7oMg.30)003. Manganese, by -15- virtue of its similar ionic radius, may possibly replace either iron or magnesium in the carbonate series. The chemical behavior of the dolomite group has been extensively studied by many authors so that only a brief pertinent consideration is necessary here. Only very minor quantities occur in the carbonate-sili- cate facies in the mineral form of ankerite Ca(Mg,PeMn) (0092. Calcium was concentrated in dolomite CaMg(003)2 as a replacement halo around chert which was then replaced by magnetite. Dolomite replacement is not a major feature and was not present in any of the tested samples. One important chemical criteria is indicated by the lack of calcium carbonate and that is the pH conditions were less than 7.8. The assmp- tion here is that there is sufficient calcium but that conditions were not sufficiently alkaline to make CaMg(c03)z stable. The remainder of the calcium is found in the sporadic apatite grains. Iron will precipitate in both an oxidizing or reducing environment under alkali conditions, but only the ferrous compounds, carbonate and magnetite, will form under a reducing environment. The carbonate has a stability field which overlaps magnetite up to a possible pH of 8.5 (James, 1954). The carbonate will begin precipitation at a pH of 5.1 under a rapidly neutralizing condition and a highly dissolved 002 content. At the stability field of 5.1 or higher a negative oxidation potential is essential. One factor which controls the amount of Mn present in the carbonate facies is the chemical equilibrium conditions. While remaining in solu- tion under oxidizing conditions, manganese begins precipitation at a pH of 7 (Krausakoff, 1951) and increases as p11 increases. Manganese will precipitate at a faster rate as the p11 rises but will always follow the ferrous compounds. Manganese carbonates are much more soluble than the iron carbonates; thus more susceptible to resolubility. Temperature has no effect on the Pe-Mn interrelationship within the ranges expected in natural environments. The facies are not in complete chemical equilibrium as noted by the associated mineral assemblages. During precipitation or shortly after the diagcnetic process had begun, limited ion migration and substitution definitely occurred. A second factor now must be explained to account for the extent of manganese substitution. The quantity of Mn cations present and the degree of precipitation to be expected under the environmental conditions have to be considered. Seventy samples similar to the facies studied were tested for manganese by wet chemical methods and loss on ignition (L.O.I.) tests. The 1.0.1. test is explained in Appendix C. A plot of the per cent manganese versus L.O.I. (Figure I) gives a point distribution approximated by a horizontal line which becomes tan- gent to the abscissa for low manganese and low 1..O.I. values. The inference drawn from the distribution is that the quantity of manganese in the facies is a function of manganese ion availability dur- ing deposition and not necessarily dependent on the pH condition which controls the CO3 radical. It can be stated that ion substitution is a function of manganese availability and to a lesser degree the amount of ferrous iron which will form stable carbonates. Magnesium carbonate precipitation is only dependent on the 003 rad- ical. Its ionic size allows free substitution for iron in the isomor- phous carbonate series. The amount of magnesium substitution is proba- bly related to the ion availability under any given physical equilibrium -17- FIGURE I 20.»..20— zo mmoq Pzwumma Q .a. w n c n O _ _ _ _ _ _ _ .L o OQuO o\ o \ oo\ 0 o o o \o I. N. 00 OO O O O O \0 o o o \ O o o o o o 0° 0 o O O O OO QO\\O I'llllo'lobllolllllkplplollIlllolblluolll \OO O O o oo o 000 o 0000 lw. O O O 0 O 00 O O O O O O O 0 O O O 0 1w o o O O O o IIQ. _ _ _ _ _ _ 0.. “W lNBOHBd condition. Mbgnesium.also substitutes on a limited scale for r.*+ in the complex silicates. Phosphorous occurs in the form of apatite. Due to the lack of as- sociated clastics most of the phosphorous can be considered a product of precipitation. If precipitated, it would be in the form‘of tricalcium phosphate Ca3(P04)2. Oxidation potentials have no effect on either cal- cium or the phosphate radical. However, the phosphate radical is very dependent on pH conditions. Ideally, a pH of 7 to 7.5 is conducive to precipitation (Krumbein, 1952). The quantity precipitated is directly related to the amount of (P04) in solution and represents a normal level to be expected in either saline or fresh water. Alminum is present in the complex silicates, possibly as a chem- ical precipitate, but the equilibrium conditions and stability fields are obscure. Its presence can be utilised to distinguish the silicates, and its excesses can show the presence of fine detrital clays. A chemical environment can be postulated from.the brief stability and equilibrium data previously presented. A pH range fromxS.l to a maximum‘of 7.8 is possible from.stability field criteria and would re- flect a reducing environment with a possible Eh range between 0 and ..2. From the sedimentary sequence both above and below the iron- forma- tion, it has been suggested that the area was part of a geosyncline inp volved in the various stages of tectonic events (Base, 1957, Van Rise, 1897). A.closed or restricted basin would allow inflowing acid streams ‘with low elastic loads to enter the basin farming brackish waters. The idea of a fresh water deposit (Bough, 1958) is possible, but the sequence of sedimentation containing algal structures in dolomite suggest at least partial brackishness. - 19 - PLATE VII Sample C-ll, plane polarized light. A fine crystalline carbonate and chert band (white) ruptured allowing the magnetite-chert- carbonate above to flow downward. A disturb- ance, possibly current or wave action, caused movement in the partially solidified facies resulting in the observed structure. Although the formation does exhibit a low metamorphic rank, the structure is believed to be primary and not the result of plastic flow. There is no continuation of the phenomena stratigraph- ically above or below the band. Two and one- half second exposure with Panatomic X. - 20 - The almost structureless character of the formation indicates a de- position zone below wave base. Certain phenomena (Plate VII) indicate that currents or occasional disturbances did disrupt the rhythmatic layv ering. The depth consideration plus the ideal MhCO3 and 3102 precipita» tion range suggests a more alkaline environment around a pH of 6.9 to 7.4. The depth does not necessarily reflect a distance fromxthe ion source as there are distinct coarse clastic zones which possibly'indicate a nearness to source. Although the environmental considerations are brief, they are nec- essary for a fuller understanding of the spectrochemical results. The problems of biological influence, state of ion transportation and source of ions have been avoided due to the inherent difficulties of each sub- ject and the remote influence they have on the direct interpretation of the results. - 21 . PLATE VIII Sample 3-16, plane polarized light. Bleb chert caused by the cohesion force in the colloidal silica which pulled a lens of the material into a bubble. The under- lying material was depressed by the weight while the overlying laminae were draped over the bleb and thinned on the top. Three sec- ond exposure with Ectachrome.x. -22- PLATE IX Sample 3-16, plane polarised light. The chart in this photograph shows total sep- aration (bleb) which resulted in depression under the thickened portion. This is proba- bly a colloidal phenomena and does not re- sult from a physical force after diagenesis. Two second exposure with Ectachrome X. PROCEDURE Each core sample was broken by a hammer blow. The chips from the inner portion of the core were chosen because the outer surface was con- sidered contaminated by the drill bit and banner blows. The chips were ground in an agate mortar and pestle to approximately -500 mesh. The equipment was washed with alcohol between each sample to prevent contam- ination. From each ground sample a .2 gram quantity was weighed out on a piece of cigarette paper and added to .2 grams of pure carbon and .02 grams of internal standard (“003). The graphite was added to stabilise the arcing (homogenity) by providing better conductivity in each sample. The internal standard used in spectrochemical analysis has four basic purposes. It is used to correct the emission errors originating from the source; to compensate for poor photographic techniques ; to cor- rect for inconsistent time settings due to mechanical malfunctions and to compensate for weight errors in the amount of each sample burned. The most important factor considered in the choice of an internal standard is the quantity of that particular element in the unknown sample and the variability of this quantity from one sample to another. For these reasons strontium carbonate was chosen for the internal standard. Strontium may substitute for calcium in carbonates. In work carried out by Vinogradov (1956) it was found that while Pro-Cambrian Ca/Sr ratios averaged fifteen times higher than Paleozoic ratios (6500 versus 350), relatively pure Pro-Cambrian carbonates had less than 40 ppm strontium -24.. present. In the carbonate-silicate rocks studied, there is very little calcium present ((100 ppm) so that the strontium content would be so low that variations would not appreciably change the strontium.line intenp sities from.the internal standard. Two samples were run for strontium but showed only traces of the element. ‘A second criteria considered in the choice of arcoa as an internal standard was its ionization potential (2.3EV) which is slightly lower than those of the elements sought. A third criteria was that Srco3 has a molecular structure which is not unlike the majority of the compounds in the samples. The mean iden- tity of molecular configurations reduces the complex molecular excitation response which often interfers with element spectra lines. A Baush and Lamb grating spectrograph (15,000 lines to the inch) was used in the experimental procedure. A low voltage DC continuous arc was sufficient to produce a spectrum. The instrument settings used were: 250 volts 0 ohms (above that of the normal system) 360 microhenries inductance 30 mdcrofarads capacitance 2400 A - 3400 A wave length span A one and one-half second pro-exposure burn was followed by a three second exposure for each sample. The pre-exposure burn was used to obtain a uniform.heat; thus cutting down the low spectra emission caused by slow ignition starts. Secondly, maximum conductivity which is essential to achieve maximum excitation is not always reached at the beginning of each arc. Finally, poor surface distribution of the elements due to the set- tling at the top of the electrode chamber is eliminated in a pre-arc burn. -25- Being unable to make a direct quantitative approach, an alternate analysis procedure was initiated with success. The premise that the photographic spectral line density is directly proportional to the quantity of the element in the sample, allows a direct quantity re- lationship between different elements or the same element in differ- ent samples when four variables are adjusted. These variables men- tioned earlier may be compensated for with reference to the internal standard. A densitometer was used to examine the spectra and record the density of a chosen spectral line for each of the elements sought. The recorded graph of each line density was measured for amplitude from.a constant lower division on the graph paper and width at that lower division point. By taking the total rectangular area under the curve, a close correlative value is obtained for intensity of the spectra emission. Internal line intensities are then equated for each spectrum, and element line intensities are adjusted up or down by a factor. The procedure which was used to develOp the photographic plates was kept as uniform as conditions permitted in order to allow accurate correlation between plates. Each exposed plate was agitated at one min- ute intervals in a solution of Kodak Dextal (700 grams per one liter of ‘water) for eight minutes. From the developer the plate was taken and placed in a stop solution composed of three per cent hydrochloric acid and water for thirty seconds. The plate was then placed in a hypo (fix) solution (Na23203) for five.minutea. Finally, the plate was allowed to dry. . 26 - INTERPRETATION Manganese variations are considered a reflection of the relative amount of complex carbonate present based on substitution principles previously described. When the manganese values increase, the mag- nesium would also be expected to increase. The trend is shown by the inclined line which represents the point average as established by the least square method (Figure 11). The significance of the point deviation above or below the line must be evaluated by using a second graph showing the relation of aluminum to magnesium. If the aluminum present is only a component of the iron silicates, the point'will re- flect the relative amount of silicate present. The apparent trend of Mg/Al values in Figure 111 would be expected with an increase in silicates containing both elements. When both point relations in Figures 11 and III are above the average, it would indicate a high per cent of carbonate and silicate minerals present. High manganese values show carbonate to be present in concentra- tions between 10-20 per cent and low values show concentrations of less than 10 per cent. Exact per cents cannot be applied due to the lack of standardization and the variable substitution of manganese in the carbonates. Silicate values range from.aero to a maximum.of five per cent. A zone (Figure 111) was chosen to indicate the transition from a pre- dominantly carbonate facies to one containing high proportions of sil- icate minerals along with various concentrations of carbonate. The -27- FIGURE II — .- .— F1 — ~ m-mo 22wm2042 mm-q. 9-4. \ e-m. oN-q __|m. ml<. 2-4. 9-0. 3-m. N-q. mloo Omno m_-m. . 2-4. 5-4 9-4. .N-o E-o. mhdzomm>>>8>>>>>>> >>>>>>>>>>>> 23 FOOTAGE SAMPLED 68 98 127 134 190 238 297 358 380 431 494 523 552 586 604 658 700 734 766 819 863 886 901 E SOL. FE FOR 10' INTERVAL 24.3 30.6 30.1 29.0 31.0 31.2 34.9 33.8 29.4 31.6 31.2 32.0 30.3 29.4 29.3 34.3 36.5 34.9 33.7 31.5 31.3 28.5 SPECTROCEEMICAL CLASSIFICATION c/c c 08 08 CS C8 CS c s/c s/c s/c slate *Core donated by the Cleveland-Cliffs Iron Company. - 39 - CROSS SECTION HOLE "A" INCLINATION -45°, BEARING DUE EAST . SCALE |"=IOO FT. ELEV.+ l598 META- DIABASE 50 C/C C MAG. CH. SIL. |.FM. H5 C ‘C C MAG.CH. CARB. |.F. c c 38l' c 0 cs cs cs cs cs MAG.CH.CARB. SIL. t. F. c 0 cs cs 0 850' S/C ARG. I. F. S/C o C.C.l. HOLE N9- 42 9,0. s/c SLATE 935' 4O FOOTAGE Z SOL. FE FOR SPECTROCHEMICAL SAMPLE 3* SAMPLED 10' INTERVAL CLASSIFICATION B 1 164 40.6 c B 2 228 32.9 c B 3 248 35.5 c B 4 273 34.5 c B 5 307 33.2 c B 6 318 35.0 8 B 7 337 30.8 8 B 8 358 32.6 8 B 9 384 34.8 cs B 10 402 32.8 cs B 11 422 32.8 a B 12 463 40.3 a B 13 512 35.5 c8 B 14 542 31.7 cs B 15 554 26.6 cs 3 16 566 22.3 cs/c B 17 576 10.6 cs/c 3TH; *Core donated by the Jones & Laughlin Steel Corporation. - 41 - CROSS SECTION HOLE "a" INCLINATION -90° SCALE VEIOOFT. ELEM +1325' _.‘ SURFACE HEM.CH. |.F-'. I35 Hr- MAG. CH. CARB. I. F — L"C “—C :C ”S —-S +—s 3I7' ~ — CS - CS - S MAG.CH. CARB. SIL. I. F. * S —CS ~—-CS _— cs 557 03/0 w-CS/C ARG. I. F. 6l2' —uL O J.8 L. HOLE N9- 848 412 FOOTAGE Z SOL. FE FOR SPECTROCEEMICAL SAMPLE 6* SAMPLED 10' INTERVAL cussxucmgou C 1 145 ---- cs C 2 214 26.9 c C 3 224 26.5 c C 4 247 26.5 ca C 5 277 27.3 c C 6 281 25.6 on C 7 301 28.5 ca C 8 366 31.3 c C 9 399 33.2 ca C 10 459 34.9 ca C 11 529 36.3 on C 12 579 37.6 on C 13 639 37.6 on C 14 696 33.6 cs C 15 739 33.0 cs *Core donated by the Jones 6 Laughlin Steel Corporation. - 43 - CROSS SECTION HOLE “C" INCLINATION -50°, BEARING DUE EAST SCALE I"=IOO FT. ELEV. +I52|' META- DIABASE \ \ .\ CS \ \ C c MAG.CH.CARB./CLASTICS I.F. CS Ccs CS 366' Cs CS MAG.CH. LF. CS CS cs 650' O J. 8 L. HOLE N9 780 MAG.CH.- CARE. LE cs 749' 44 .APPENDIX B The following charts represent the measured data.obtained from the densitometer graphs. Measurement of amplitude was taken from a constant base line and width values were taken between the two graph lines which intersect the base line. The measurements were made in centimeters so that the area is in square centhmeters. The type of scale is unimportant as the only significant factor is the use of a standardized scale for all data. - 45 - On It .20 r40 .50 I'60 .70 I... I'90 AL— 3082 X I GRAPHICAL REPRESENTATION OF PHOTO DENSITY LINES As RECOROEO ON THE DENSITOMETER O Mn-2795 A 450 Mg — 2797 A I04 20- 30- 40. 50 d 604 70-‘ -45- oa.w~ m~.~ mN.n : ao.m oo.H on.NH an.h aw.n : am.w ea. o~.m~ nh.m No.9 : m~.m hm. da.m o~.oH mw.m : H~.e o~.~ om.e h¢.~ oo.m : oo.m mm. N¢.n qm.m ow.m : om.w hm. mn.¢ oo.H~ qm.o : 05.3 mo.a o~.n~ mm.o ow.m : o~.~ Nb. ea om.m oN.n mn.m : o¢.a no. a 0m.o mm.“ mm.h : ¢~.w hm. w QN.¢ OH.a hw.o : mw.m on.H n sn.n o~.o~ m¢.o : mo.m nm.~ o mH.n oh.» m~.h : uo.o ~N.a m ne.c mu.n Hm.h : mm.» so. Q om.N on.m o¢.o : nm.m ¢¢.~ m m¢.¢ Om.n mm.h : w¢.o «a. N on.n qm.n 0H.h oo.m on.h oo.~ H m=A<§ nmfiuumuoo mzaqo> NDA¢5 ouaoummoo mzaao> NDA<> omaoummoo mzfidos MOHU omsoummoo mzano> d n¢s~ ummz¢wz¢z mm.¢ mw.< oo.~ mo.n cm.m cm. dw.m «0.0 mm. am.m mq.¢ aN.H om.m -.¢ mm. mN.m mm.m mm. mo.m om.m mo.H ho.¢ mo.m Nu. du.¢ nm.m mm. wm.m mm.n mm. oo.¢ aa.~ om.H nm.¢ ~¢.N nm.~ No.¢ «n.m ~N.H mn.~ Nm.u hm. an.~ ¢~.H <¢.H o~.m om.n «a. No.¢ cm.¢ oo.~ wands nuaoummoo mzaflo> MOHU nmaommmou Nxsgo> ¢ mnnu mDomommmomm hmx‘ro—OQNU‘.\TOM NNmoox'rdwoCJv-I 0 Inlnx'thtfixoch‘ ”ONBHHQMU‘ ”WOQMH o o s 00. so... 0 MOQMQQmmood'wLfiI-flowa‘ momuaomox't O‘NHGBONQ‘u—dwu—I O m .m. m mm mand> omauummoo MEDAO> % swam ZOOHAHm mm M oo.~ om. mm. a~.H mm. mm. wo.~ Nu. mm. mm. om.~ nm.~ an.“ Na. ¢¢.H «a. oo.H mOHD¢N « m onhummmoo Humq'mxoh o-Iv-Ir-Iu-It-lu-Iv—i v—led'I-HONQO‘S g... -43- .. assesses \Dfi’melflml-nwhfinoelfi cur~.4~sr~\o<:In-¢¢n MDA u=A¢5 omkommmoo uzaao> d awnn.ZfiHHzomHm « M «a m¢.H Nm.a No.~ eo.~ om. mm. 5n.H am. ma. «5. 5m. 5m. cw. o5.~ ma. «Ohodfi ZOHHUMMMOU HNMQWQI‘QO‘S -49- 00.H 00.« 50.0 00.0 ««.0 0«.0 00.H 50.0 0«.0 00.« 00.0 0H.0 00.H «0.« 00.0 HMMNWNWNQWO¢QWH s so. as QHNMHWMMHCW¢Q¢HH #NMMMQMOMOOOQHQ MDA¢> nmhommmoo l MEDAO> d 005« mmmz¢uz 4 505« ZSHmmz0 4 000« 00000000000 05.5 00.00 0«.0 0«.0 00.0 00.0 00.00 00.00 0«.0 00.0 00.5 00.0 05.0 00.00 00.0 QNMQQHO O. mex'I'O‘OsxDOS 0 00050000050 00 q o 00.0 «5.0 50.0 05.0 00.5 00005 008000000 m:000> < 000« 2000000 0. mm. m w. 0.0.. 0 m 00.0 «0.0 «0.0 00.0 00. 00. 50.0 00. 00. «0. 50. 50. 00. 05.0 00. 009040 zOHHUMmmoo 0Nm0tn HHHF‘IH HNMQWGFQO‘S 0 -51- «0.5 00.5 gunman-406nm s s 6 00061005 00o000 O NOQQOO QC‘HI‘MNI‘ . O 0000N0000000000000N05 ”3.353 O‘COHNmONO 00MM~DO~¢> O ”6101-!” @QNVfiQ . ,4 00308 S .0... @OMMQNHNOONBQMNMNONd'M WI" 36 860 0 «000 20202004 00.0 00.«0 50.0 50.0 00.5 00.00 05.00 00.00 00.0 0«.5 00.5 00.00 00.0 0«.«0 00.00 00.0 00.0 00.0 00.5 00.0 05.0 00.0 .0 s o o o O‘GQQNNOGO‘O‘C‘ONBQQQCBQ . . . . . . . . . .0 N 50005000 NNOO‘HO O 0 ma 5. o- a. .- .- .5 = 5. .- 2 a. .- 00.0 0 . O . . O .0 0 50 00000 550 0080538000008000 ......... thd’d‘QOOONV‘lfllfiO‘hmfl’O 000 on ”N s 00.«« 00.0« m 00005 009000000 02:00> 00005 009000000 020005 00005 009000000 02000> d 0«00 2000 d 0000 200920090 «mam 0«.0 00.0 50. 00. «0. 00.0 00.0 00.0 00. 05. 05. 00.0 00. 05.0 00.0 50.0 00.0 00.0 05. 50. 00. 00. 00. 0090<0 20H9000000 HNWQ’WONwO‘Ov—INM HHv-IHr-OF-IHHHNNNN 0«00005002 -52- qn. m0. mm.¢ 0m.m 0«.0 m0. N0. m¢.o Na.n 00.0 00.0 00.0 0n.n eh.n mm. 00. 00.0 «0.N no.0 0«. mm. m0. 00.~ m~.m N0. 0N.N 0m.0 00.0 mn.¢ 0m.0 50.0 00.0 00.n nm.n m¢.0 mn.0 ha. -.n n0.n m¢.0 nu.~ nm.m 00.0 00.0 «0. NN.N mm.~ qo.¢ n¢.m 05. Nh.~ mm.n wm.¢ nn.0 on. 50.0 m¢.n 0m.n 0«.0 00.0 Nm.m 00.m 00.5 00.5 mm. hm.N mm.0 05.0 00.n 05.0 hn.N 00.0 «0.0 au.n 00.0 m¢.u n0.~ 00.0 00.0 h0.0 0N.N 00.N «5.« 0m.¢ 00.0 «0.0 00.0 ao.m 0m.n no.0 m0.n 50.0 00.0 00.0 ms. Nd. 0«.0 nn.m 0m.n hm. 00.0 w0.n ma.0 nn.n on. mw.0 m0.n m0.~ 00.0 mm. 00.~ on.m qw.~ 00.5 mm. HNMQMOBQO‘S 53 - 00005 008000000 0:000> 4 mahu 00004020: 00005 00H000000 02000> 4 mama 20000204: 008040 onH000000 « mmmm «Hfim 00.N 99.0 on.» Hm.0 0«.0 m0. m0. «0.0 no.0 00.0 m¢.0 no.0 00.0 «0.0 um. 00.0 mm.~ 0m.N N0.n N0. 0¢.n 00.0 00.n nn.n mm. 90.0 00.0 mn.0 0n.n 0n.0 0m. 00. mm.m 00.0 m¢.0 an. 0N. m9.0 «9.0 m¢.0 0m.n ~¢.m m0.n no.0 00. 00.m mm.m 0m.9 mm.0 on. 00.m 00.0 00.0 00.0 on. 0«.0 00.m 00.0 ~h.n 00.0 0n.¢ 009000000 0:000> 000<5 009000000 0:000> 0090<0 2009000000 0 mmnu m0000000000 0 000w z0000Hm « mmmm «0.24.0 HNMd’lfi‘ONQO‘Ov-INM HHHHHF‘HHHNNNN -54- HNMfi‘nVDNCDO‘O H APPENDIX C Loss on ignition tests determine the amount of volatile material in any given rock. When applied to carbonate-silicate facies, it is possible to determine the amount of carbonate present by the per cent of 002 driven off. A weighed sample is placed in a platinum crucible and heated for two hours at lOS'C. when the moisture has been evaporated the sample is weighed to determine the loss. The crucible is then placed in an oven for one hour at lOOO‘C. after which the remaining sample is weighed. The end weight subtracted from the original weight minus the moisture determines the per cent of CD: that was voletilized. - 55 -