Showing papers in "Economic Geology in 1963"
TL;DR: In this article, the authors present a new science leading to such an approach, namely geostatistics, which is a new approach for estimating the estimation of ore grades and reserves.
Abstract: Knowledge of ore grades and ore reserves as well as error estimation of these values, is fundamental for mining engineers and mining geologists. Until now no appropriate scientific approach to those estimation problems has existed: geostatistics, the principles of which are summarized in this paper, constitutes a new science leading to such an approach. The author criticizes classical statistical methods still in use, and shows some of the main results given by geostatistics. Any ore deposit evaluation as well as proper decision of starting mining operations should be preceded by a geostatistical investigation which may avoid economic failures.
4,203Â citations
TL;DR: Aqueous and non-aqueous inclusions in 84 samples of various minerals from a wide range of geologic environments were studied with the freezing stage in order to gain an insight into the range of concentrations and compositions of fluid inclusions as mentioned in this paper.
Abstract: Aqueous and non-aqueous inclusions in 84 samples of various minerals from a wide range of geologic environments were studied with the freezing stage in order to gain an insight into the range of concentrations and compositions of fluid inclusions. Inclusions in most Mississippi Valley-type ore minerals contain highly concentrated saline solutions, showing freezing temperatures between --23.4 degrees and --10.5 degrees C; minerals from ore deposits of more typically hydrothermal affiliations mainly show temperatures of --9.4 degrees to nearly 0 degrees C; and inclusions in quartz crystals from sedimentary, metamorphic, and igneous rock environments show a wide range of freezing temperatures. Inclusions in pegmatite minerals in particular vary over a wide range, from the most concentrated solutions found in any inclusion (> 40% salts) to fairly dilute solutions ( 2 . Other geologic environments sampled include Colombian emerald, pegmatitic topaz and fluorite, the Triassic traprock zeolite assemblage, and sedimentary halite beds.Not all the phenomena exhibited by inclusions at low temperature are completely understood at present but several crystalline hydrate phases, such as NaCl.2H 2 O and CO 2 .5 3/4H 2 O (structural formula 8CO 2 .46H 2 O), are shown to be stable in inclusions of appropriate composition even at temperatures above 0 degrees C, and probably exist in the inclusions in natural rocks in polar regions. More significantly, the formation and recognition of such phases aid in establishing the gross composition of individual inclusions far too small for chemical analysis.The data obtained are useful in a variety of ways, such as: discriminating among gas, liquid, and supercritical fluid, and among liquid water, liquid oil, and liquid CO 2 in inclusions; improving precision of the pressure corrections applied to inclusion filling temperature determinations; proving the general lack of leakage into or out of inclusions; estimating the minimum pressure at the time of deposition of certain samples; verifying the lack of extraneous solid crystallization nuclei in the inclusions and hence their formation from exceedingly quiet, clean solutions; determining the total equivalent NaCl concentrations and some information concerning the composition of the fluids from which ores have formed; and determining changes in the composition of the fluids bathing a single crystal during its growth, and at certain times throughout its history.
137Â citations
TL;DR: In this paper, the chemical composition and relative deuterium concentration of primary fluid inclusions in ore and gangue minerals from the Cave-in-Rock and Upper Mississippi Valley districts -both of which are of the Mississippi Valley type.
Abstract: This paper describes the chemical composition and relative deuterium concentration of primary fluid inclusions in ore and gangue minerals from the Cave-in-Rock and Upper Mississippi Valley districts - both of which are of the Mississippi Valley type. Compositional changes are compared to the paragenetic sequence. The fluid inclusions in the early ore minerals are nearly saturated sodium-calcium chloride brines. Fluid inclusions in late minerals are less concentrated and have a lower relative deuterium concentration. In the Cave-in-Rock district the composition of primary fluid inclusions in yellow fluorite, the earliest ore mineral, is similar to that of connate water in the Illinois basin in the same strata as the ore deposits. The change in composition of fluid inclusions in the later quartz and sulfide minerals indicates a water of different origin, possibly magmatic, was introduced. Connate and possible magmatic waters were largely flushed out during deposition of the gangue minerals in the last stages of mineralization, and the composition of the fluid inclusions in these gangue minerals trends toward that of meteoric water or a dilute mixture of meteoric and magmatic water. In the Wisconsin-Illinois-Iowa district, fluid inclusions in the ore minerals are highly concentrated sodium-calcium chloride brines that have a high relative deuterium concentration; inclusion fluid in late gangue minerals contains less deuterium and is relatively dilute.
120Â citations
TL;DR: In this paper, the authors test the hypothesis that regional variation of sulfur in coal beds is related to the influence of penecontemporaneous marine water by using stratigraphic and statistical methods.
Abstract: The hypothesis that regional variation of sulfur in coal beds is related to the influence of penecontemporaneous marine water is tested by stratigraphic and statistical methods. The Lower Kittanning coal exhibits regional variations in sulfur content which are statistically related to the regional changes in overburden, areas of marine overburden being higher in sulfur than continental areas. The Upper Freeport coal, overlain entirely by continental beds, shows no regional sulfur variation. The conclusion is made that the presence or absence of marine waters was one of the factors controlling regional variation of sulfur in coal.
118Â citations
TL;DR: In this paper, a method was developed for the extraction and chemical microanalysis of individual fluid inclusions, or groups of inclusions in the milligram range, in the mineral samples.
Abstract: A method has been developed for the extraction and chemical microanalysis of individual fluid inclusions, or groups of inclusions, in the milligram range. Usable quantitative analyses for Na, K, Ca, Mg, Cl, B, and SO 4 have been obtained of mineral samples containing several milligrams of inclusion fluid, and with increased experimental errors, on fractional milligram samples. The steps involved are: 1) concentration of inclusions by sample selection and cutting; 2) electrolytic cleaning; 3) crushing in soft Cu sample tube in vacuo; 4) conversion of emitted water to H and determination of its volume; 5) mass spectrometric determination of the D/H ratio if desired; 6) leaching of the crushed mineral to dissolve soluble salts remaining; 7) microanalysis of the filtrate by sensitive colorimetric and flame photometric methods. The method has been applied to determine the composition of fluid inclusions in mineral samples from several types of deposits, with special attention to a series of samples from Mississippi Valley-type ore deposits.
57Â citations
TL;DR: In this paper, the authors made numerous semiquantitative analyses of specimens, largely from 9 western [U.S.] states, selected carefully from 5 groups of geologic environments, in the hope that the frequency and percentages of some elements might be distinctive of the several geologic groups.
Abstract: In an earlier paper by 2 of the authors the conclusion was reached that the 33 recognized species of oxides of Mn could be separated into 3 groups: 1) those which appeared to be persistently supergene in origin, 2) those which appeared to be persistently hypogene, and 3) those which were supergene in some localities and hypogene in other localities. When that paper was written, there were available about 250 X-ray diffraction analyses of mineral specimens, also 35 complete and about 150 partial chemical analyses. The conclusions of that paper were based upon the interpretation of the geologic conditions under which these specimens occurred. Late in the preparation of that paper, it seemed worthwhile to make numerous semiquantitative analyses of specimens, largely from 9 western [U.S.] states, selected carefully from 5 groups of geologic environments, in the hope that the frequency and percentages of some elements might be distinctive of the several geologic groups. For this purpose, 95 specimens were selected from the 5 groups, as follows: 19 specimens interpreted as supergene oxides by the geologists who collected them, 35 specimens of hypogene vein oxides, 22 specimens of Mn-bearing hot spring aprons, 9 specimens of stratified oxides, and 10 specimens of deep-sea nodules. The spectrographic analyses here recorded indicate that a group of elements - W, Ba, Sr, Be, As, Sb, Tl, and Ge - are present more commonly, and largely in higher percentages, in the hypogene oxide than in the supergene oxides and thus serve to indicate different sources of the Mn. Also, the frequency and percentages of some of these elements indicate a genetic relation of the manganese oxides in hypogene veins, hot spring aprons, and stratified deposits. The analyses indicate a declining percentage of some elements from depth to the surface in these 3 related groups and increasing percentages of some other elements. It is concluded that some of the elements in deep-sea nodules indicate that sources other than rocks decomposed on the continents, probably vulcanism on the floors of the seas, have contributed to their formation.
53Â citations
TL;DR: In this paper, the authors deal with the reflected infrared analysis of several common minerals, rocks, and meteoritic materials, and the typical spectra to be obtained from quartz plates, fused silica and glasses are briefly reviewed and recent spectral data from minerals and rocks are examined.
Abstract: The earliest studies of minerals by reflected and emitted infrared radiation were those of Coblentz (1, 2). Since then mineralogical uses of reflected infrared radiation have been restricted primarily to studies of glass, and to minerals like quartz and cristobalite which play a prominent part in the understanding of glass structures. In a similar manner infrared emission studies have been restricted almost exclusively to ceramics and refractories. This paper deals with the reflected infrared analysis of several common minerals, rocks, and meteoritic materials. The optical principles involved, and the typical spectra to be obtained from quartz plates, fused silica, and glasses are briefly reviewed and recent spectral data from minerals and rocks are examined. Similarities and differences between absorption and reflection spectra for the same materials are discussed, and some of the problems encountered in the calculations of composition (modal analysis) are indicated.Applications to nondestructive testing of polished rock surfaces (or gems) and to the calculation of ambient-temperature emissivity curves for rocks are shown. Such spectral emissivity curves are an important prerequisite for the remote mapping of the lunar and other planetary surfaces.
49Â citations
TL;DR: In this article, the authors investigated the FeS 2 -NiS 2 join in the S-rich portion of the Fe-Ni-S system and concluded that most of the Ni occurs in metastable solid solution in these pyrites.
Abstract: The S-rich portion of the Fe-Ni-S system has been investigated between 100 degrees and 1000 degrees C. under equilibrium vapor pressures with especial emphasis on the FeS 2 -NiS 2 join. Pyrite (FeS 2 ) and vaesite (NiS 2 ) coexist between 729 degrees + or - 3 degrees and 137 degrees + or - 6 degrees C. Above this temperature range, a (Fe, Ni) (sub 1-x) S solid solution coexists with S liquid, whereas below 137 degrees C. bravoite [(Fe, Ni)S 2 ] is stable on the join between pyrite and vaesite. The solubility of FeS 2 in vaesite is a maximum of 27.9 wt % at 729 degrees C.; other points on the solvus are 13.5% at 600 degrees C, 6.5% at 500 degrees C, 2.5% at 400 degrees , 0.7% at 300 degrees , and 0.1% at 200 degrees C. The heat of mixing, delta H, is constant at 9.8 kcal/mole. The maximum NiS 2 solubility in pyrite of 7.7 wt % also occurs at 729 degrees C. It decreases to about 6.8% at 700 degrees C. but could not be determined at lower temperatures. When pyrite and vaesite coexist, the vaesite solvus is a useful geothermometer. A determination on material from the Kasompi Mine, Katanga, indicates a formation temperature of 390 degrees C. Bravoite, generally a secondary mineral, can form only below 137 degrees C. C. Most nickeliferous pyrites were deposited at relatively low temperatures where the equilibrium Ni solubility is well below 1%. It is concluded, in the light of the experimental evidence, that most of the Ni occurs in metastable solid solution in these pyrites.
36Â citations
35Â citations
TL;DR: In this article, the authors considered the arrival of anomalously distributed elements by submarine springs into the lagoonal environment of the depositional basin is probably the most satisfactory of three possible explanations of the abnormally distributed elements.
Abstract: The basal member of the Zechstein (Permian) carbonate rock sequence of southeastern Durham is considered the product of accumulation of carbonates and/or mud alternating withaccumulation of bituminous matter during a long slow process of sedimentation. The distribution of most minor elements reflects normal weathering of the land surface, but the contents of zinc, lead, barium, and, in places, copper exhibit a variation that does not conform to any pattern that could be related primarily to rate of sedimentation. Intermittent introduction of the anomalously distributed elements by submarine springs into the lagoonal environment of the depositional basin is probably the most satisfactory of three possible explanations of the source of the abnormally distributed elements.
32Â citations
TL;DR: Biotites from several Basin and Range monzonitic stocks have been analyzed for Cu, Pb and Zn as mentioned in this paper, and the comparisons show the following correlations: 1) each stock or district belongs to its individual trace base-metal concentration population.
Abstract: Biotites from several Basin and Range monzonitic stocks have been analyzed for Cu, Pb and Zn. These data have been compiled for biotites from the Tintic, Bingham, Park City-Little Cottonwood, Iron Springs, San Francisco and related districts, the Gold Hill mining district, also the Mineral Range stock, and the Ibapah stock, all in Utah. Similar data have been compiled for the Ely district and the Whitehorse Pass stock in Nevada. The biotites were analyzed spectrochemically on an Applied Research Laboratories, 1.5 m, 24,000 line per in. grating spectrograph. In was used as an internal standard. The F test was used to establish the equivalence the variances of base metal concentrations in biotite from groups of individual stocks or districts. A graphical comparison of geometric means and standard deviations of the base metal content of biotites from the individual stocks and districts was examined and visual estimates of differences and similarities were noted. The comparisons show the following correlations: 1) Each stock or district belongs to its individual trace base-metal concentration population. 2) Contrasting correlations exist between base-metal concentration of biotite and base-metal production in the sampled areas. High Cu content is associated with Cu production, whereas low Pb and Zn content is associated with Pb and Zn production. 3) Biotites from hydrothermally altered stocks contain more Cu and less Pb and Zn than unaltered stocks. 4) Trace base metal content of biotite is an indicator of base metal mining districts in the Basin and Range province.
TL;DR: In this paper, an isochoric method is described by which hydrothermal measurements may be made up to 7500 psi at 25 degrees C or 4000 psi at 400 degrees C. for 1) solubilities of minerals, 2) mineral synthesis, 3) P-V-T relations of gases and liquids, 4) conductivities of liquids and 5) rates of reaction where traceable by changes in pressure or solubility.
Abstract: An isochoric method is described by which hydrothermal measurements may be made up to 7500 psi at 25 degrees C. or 4000 psi at 400 degrees C. for 1) solubilities of minerals, 2) mineral synthesis, 3) P-V-T relations of gases and liquids, 4) conductivities of liquids, and 5) rates of reaction where traceable by changes in pressure or solubility. Solids, a gas, and a liquid are added in weighed amounts to the evacuated reaction vessel without contamination and then agitated by rocking while being heated. Leaching of the chrome-plated, stainless steel vessel by aqueous 4.1 m NaHS solutions to 200 degrees C. added only 10 ppm Ni and 15 ppm Cr as background. Solubilities are determined by analysis of samples of either liquid or gas phases which are taken by a double valve system in a 2 step process; small (5 ml) samples are first separated at pressure and temperature from a large reaction vessel (about 1100 ml capacity) by a nearly isothermal, isobaric process, and then are withdrawn into a glass container near standard conditions. More than 12 samples may be extracted at various temperatures and pressures from one charge of the vessel with reproducibility of duplicates within the analytical error of + or -2%.
TL;DR: In this paper, an hypothesis of lateral secretion by water of compaction is presented as a possible explanation of the genesis of certain problematical types of ore deposits. But this hypothesis has been widely disputed.
Abstract: An hypothesis of lateral secretion by water of compaction is presented as a possible explanation of the genesis of certain problematical types of ore deposits. These deposits, including sandstone-type V-U deposits of the Colorado Plateau and Mississippi-Valley-type Pb and Zn deposits, have features suggestive of formation by ground water, but proposed explanations of the processes of formation have been widely disputed. It is proposed that water expelled from sediments during compaction may have been the ore-forming fluid. Such water might contain metals in solution prior to burial, as well as metals acquired during diagenesis of the enclosing sediments. Expulsion of the formation fluid must have taken place in huge volume; this volume of fluid, even if highly dilute with regard to ore elements, might have contained sufficient metals to have formed the numerous, widely distributed deposits characteristic of the Colorado Plateau and Mississippi Valley regions. Expulsion of the fluid probably would take place largely through transmissive zones, which could become the loci of major ore concentrations. Numerous smaller deposits may have been formed from smaller-scale expulsion through zones that transmitted less fluid. Flow of formation water during compaction appears to be a more logical source for the widespread small deposits than penetration of consolidated sediments by extrinsic fluids as proposed in previous hypotheses.
TL;DR: Chalcopyrite was prepared from precipitates of CuS and FeS in distilled water at room temperature and at 150 degrees C as mentioned in this paper, and it was transformed to bornite by holding it at 100 degrees for six days in a copper sulfate solution providing the requisite excess Cu (super ++) ions.
Abstract: Chalcopyrite was prepared from precipitates of CuS and FeS in distilled water at room temperature and at 150 degrees C. The resulting chalcopyrite transformed to bornite by holding it at 100 degrees for six days in a copper sulfate solution providing the requisite excess Cu (super ++) ions, and the bornite reconverted to chalcopyrite under similar conditions in the presence of excess Fe (super ++) and S (super =) ions. The significance of the low- temperature synthesis of copper-iron sulfides, and of additional experiments in which the finely divided precipitates were recrystallized at low temperature and high pressure to form coarsely crystalline sulfides, for an understanding of conditions of formation of syngenetic sedimentary ores is noted.
TL;DR: The formation of high-grade residual bauxite deposits in tropical regions is dependent on numerous complicated interrelating factors, a balance that is easily upset by even the slightest changes in conditions as mentioned in this paper.
Abstract: "The formation of high-grade residual bauxite deposits in tropical regions is dependent on numerous complicated interrelating factors--a balance that is easily upset by even the slightest changes in conditions. Some attempt is made here to analyze the most important of these--paying particular attention to the contrasted compositions of the endproducts produced."
TL;DR: A more precise term is needed for the process of mobilization of elements from a solid rock and their transportation and redeposition elsewhere; for this process, the authors proposed the term "lithogene" ("stone-born") to stress the source and process as do "magmatic" and "sedimentary".
Abstract: Much of the disagreement over "epigenetic" and "syngenetic" deposits is semantic; some ores and altered rocks are in part syngenetic and in part epigenetic and for them the term "diplogenetic" is proposed. All these terms are primarily time terms related to the contemporaneity of the deposit and the enclosing rock, but in a secondary sense they are space terms; they do not, however, imply process of formation or source of the chemical constituents. Process or source terms such as "magmatic," "hydrothermal," "sedimentary" are generally satisfactory, but the process term "lateral secretion" is now vague in meaning. A more precise term is needed for the process of mobilization of elements from a solid rock and their transportation and redeposition elsewhere; for this process I propose the term "lithogene" ("stone-born"), to stress the source and process as do "magmatic" and "sedimentary." Such deposits could be derived from syngenetic, diplogenetic, or epigenetic deposits through the action of metamorphic, hydrothermal, supergene or other solutions. If one wishes, however, to emphasize the distance the mobilized elements have moved from the source rock, the resulting deposit can be described best as a locally derived lithogene deposit ("lateral secretion"), or as a regionally derived lithogene deposit ("product of regional metamorphism").The classification of many deposits such as epigenetic replacement bodies of magnetite in limestone, and syngenetic gold in recent placers is not controversial; however, where large parts of the mineral deposit are made up both of syngenetic elements and introduced elements, the term "diplogenetic" is appropriate. Examples include mineral deposits in which syngenetic cations are united with epigenetic anions, as in fluorite replacements in limestones, or where the reverse relationship holds and epigenetic cations are united to syngenetic sulfur or other anions--as may be true of certain black cupriferous shales of the Mansfeld type. Guides for distinguishing the various types of mineral deposits are discussed at length and include: mineralogy; texture; isotopic composition of hydrogen, carbon, oxygen, sulfur, and perhaps other elements; form; age relations; alteration; zoning; position and quantitative adequacy of supposed source rocks; lithology; structural geology; paleogeography; and regional geologic relations. The criteria developed are used in a critical review of several examples of controversial deposits--including the African Copperbelt deposits and those of the graphitic schists of Fenno-Scandia.
TL;DR: In this paper, the authors investigated the properties of resinite from bituminous coals of varying rank and found that some of the resinite occurred as thin films on cleat surfaces rather than as discrete globules.
Abstract: During an investigation of the composition and optical properties of resinite from bituminous coals of varying rank, it was found that in samples from the Northumberland coal field (England) some of the resinite occurred as thin films on cleat surfaces rather than as discrete globules. It is concluded that pressures and temperatures attained in the Northumberland seams under increasing depth of burial were sufficient to melt the resinite, without inducing any additional physical or chemical change, and permitted migration in the fluid state over short distances. Migration of resinite has not previously been recorded in bituminous coals, although analogous but more extensive effects have been described in thermally altered lignitic coals of Bohemia, Czechoslovakia.
TL;DR: The mean Mn/Fe ratio of 94 samples of Precambrian sedimentary Fe formations is 0.025 which is very close to the crustal average of 0.022 for this ratio.
Abstract: The mean Mn/Fe ratio of 94 samples of Precambrian sedimentary Fe formations is 0.025 which is very close to the crustal average of 0.022 for this ratio. Post Precambrian ironstones, on the other hand, show a mean Mn/Fe ratio of 0.009 indicating a marked geochemical separation of these metals. The Mn/Fe ratios of Precambrian Fe formations exhibit a significant correlation with the degree of oxidation of the samples, whereas this correlation is absent in the younger ironstones. Ores formed on the Precambrian Fe formations in the Lake Superior region generally have abnormally low Mn/Fe ratios (0.009), as do the ores formed from the younger ironstones. The Mn/Fe ratio of a chemical sediment may be influenced by the source rocks, by selective dissolution at the source, by separation during transport, by the conditions of the depositional environment, and by diagenetic modifications. It is suggested that the present data and other chemical characteristics of Fe formations may best be accounted for by assuming a lower O content in the Precambrian atmosphere.
TL;DR: In this paper, a colorimetric indicator reagent that reacts quantitatively with Cu, Pb, and Zn is used to determine only a small fraction, normally about 5%, of the total metal content of strictly residual soils.
Abstract: Rapid methods of analyzing soils and stream sediments for readily extracted ore metals have been widely used in mineral exploration. The methods in most common use involve the simultaneous treatment of the sample with 2 immiscible liquids, one a cold aqueous extractant, and the other a solution of dithizone in toluene or hexane. Dithizone is a colorimetric indicator reagent that reacts quantitatively with Cu, Pb, and Zn. These procedures determine only a small fraction, normally about 5%, of the total metal content of strictly residual soils. Where the metal in the soil or sediment is not residual but has originated by precipitation from metal-rich natural waters, the fraction extracted may be substantially higher than 5%. Procedures for the dithizone field tests are described in detail, the chemical reactions are explained, and some common operational problems are discussed.
TL;DR: The ores were formed by leaching of silica and residual concentration of insoluble iron oxides in extensively deformed, recrystallized ferruginous cherts of the Precambrian Imataca series.
Abstract: The ores were formed by leaching of silica and residual concentration of insoluble iron oxides in extensively deformed, recrystallized ferruginous cherts of the Precambrian Imataca series Physical types include so-called crustal ores, consisting of hematite grains in a matrix of secondary goethite and characterized by a banded structure inherited from the bedding of the iron formations, and friable ores, porous aggregates of hematite grains which extend downward below a transitional zone of semifriable, platy ores to depths of as much as 800 feet Sampling of spring waters which issue from levels at or below the lower margins of the ore bodies and other evidence indicate that silica is being removed at the rate of about nine tons per year, that iron ore is being formed at the rate of 18 tons per year, and that the amount of ore now present could have been formed (under present-day climatic conditions) in only 20 million years, or since Oligocene time
TL;DR: In this paper, the authors reported that the ore minerals of the mine are scheelite, wolframite, molybdenite, bismuthinite and tetradymite.
Abstract: "The ore bodies which are localized in several calcareous shale beds within the upper Cambrian sediments are lenticular in shape, and are essentially parallel to the bedding of the host rocks. Among the several ore beds only one, the main ore bed, is productive. The ore minerals of the mine are scheelite, wolframite, molybdenite, bismuthinite and tetradymite. Among them tetradymite had not been previously reported from this mine. The metal content of the ore and the intensity of the wall-rock alteration are roughly proportional to the abundance of quartz veins."
TL;DR: In this paper, a detailed analysis of the complex structural pattern revealed the presence of two fracture systems: the A-system is slightly older than the B-system, and their origin is ascribed to two couples approximately perpendicular to each other with the intruding granite as principal force.
Abstract: "There are two types of deposits: (1) In the vicinity of Rooiberg village, cassiterite ore bodies were formed by replacement within a stratigraphically defined, orthoclase-rich arkosite horizon. Petrofabric analyses helped to establish a system of shear and tension fractures that served as channelways for the oreforming solutions emanating from the granite. Insignificant metal values only have been located in these fractures. The mineral paragenesis of the pockets is dominated by tourmaline, cassiterite, carbonates, and a variety of sulfides (pyrrhotite, pyrite, chalcopyrite, bismuthinite, sphalerite, galena). (2) In the Leeuwpoort area, a number of cassiterite lodes are mined. Detailed analysis of the complex structural pattern revealed the presence of two fracture systems: The A-system is slightly older than the B-system. Their origin is ascribed to two couples approximately perpendicular to each other with the intruding granite as principal force. Fractures of both systems have
TL;DR: The pegmatites are discordant, steeply dipping, tabular bodies in the Penobscot quartz-mica schist near the Waldoboro granite as mentioned in this paper.
Abstract: The Peg Claims pegmatites are located SW. of Rockland in the towns of Warren and Cushing, Knox County, Maine. These pegmatites are representative of a group of zoned, granitic, Li-bearing pegmatites in which spodumene is present nearly from wall to wall. The pegmatites are discordant, steeply dipping, tabular bodies in the Penobscot quartz-mica schist near the Waldoboro granite. A narrow quartz- tourmaline-muscovite-apatite aureole is commonly developed around each of the pegmatites and around inclusions of country rock in the pegmatites. The pegmatites are zoned, and each may be subdivided into: 1) a narrow quartz-muscovite border zone; 2) a narrow albite-quartz-muscovite wall zone; and 3) an albite-quartz-spodumene-perthite core that constitutes most of the pegmatite. Cross-cutting, fine-grained, quartz-albite-spodumene-muscovite lenses are found within pegmatite cores. The bulk mineralogy and variations in the mineralogy from zone to zone of the largest body (Dike 1) were determined by megascopic mineral point-counts. There is a decrease of albite, quartz, and muscovite and an increase of spodumene and perthite from the border and wall zones into the core. The alkali contents of Dike 1 and of each of its zones were determined by flame photometer and X-ray fluorescence analyses. The amount of Na 2 O decreases and the amounts of K 2 O, Li 2 O, Rb 2 O, and Cs 2 O increase from the border and wall zones into the core. Estimated bulk compositions of Dike 1 and of each of its zones were computed. It is concluded that the distribution, structural features, bulk chemistry, and the mineralogical, chemical, and textural zoning of the pegmatites are consistent with development by fractional crystallization of a pegmatitic fluid in a restricted system.
TL;DR: A study of the pyroxene amphibolite host rock at the Scott magnetite mine, Sterling Lake District, New York, indicates that it could have been the source of the magnetite ore as discussed by the authors.
Abstract: Study of the pyroxene amphibolite host rock at the Scott magnetite mine, Sterling Lake District, New York, indicates that it could have been the source of the magnetite ore Titrimetric, optical emission spectrographic, and fluorescent X-ray analyses show that the percentage of Fe in the mafic silicates and total rock decreases with proximity to the ore zone In addition, much of the amphibolite has been replaced by gneiss and pegmatite and some of the Fe thus removed is believed to have migrated to the ore zone to form magnetite The percentage of mafic silicates and magnetite in the amphibolite shows no systematic increase or decrease toward the ore zone All of the constituents found in the ore bodies were available in the host rock Highly dispersed material was released from amphibolite and concentrated into ore bodies in favorable structures Magnetite ore has replaced pyroxene amphibolite along a low-pressure zone where the structure of the host rock changes markedly Movement of material was largely along foliation, lineation, and grain boundaries, and, to some extent, through crystals by diffusion The energy required to activate and move the elements from the mafic silicates of the host rock is believed to have been supplied by temperature and pressure changes during metamorphism, and by the introduction of replacement gneiss and pegmatite The data presented are explained best as a result of metasomatism accompanying regional metamorphism and granitization
TL;DR: A detailed study of the microstructure and composition of lower Gondwana coals of the Barakar stage (Permian) of the Talcher field, Orissa, India, shows them to be noncoking to feebly coking, high volatile bituminousrank, indistinctly banded coals composed mainly of durain with subordinate vitrain and fusain this article.
Abstract: A detailed study of the microstructure and composition of lower Gondwana coals of the Barakar stage (Permian) of the Talcher field, Orissa, India, shows them to be noncoking to feebly coking, high- volatile bituminousrank, indistinctly banded coals composed mainly of durain with subordinate vitrain and fusain.
TL;DR: In this article, it is concluded that the bauxite resulted from the removal of silica and iron by leaching when kaolinitic clays, developed from aluminarich bedrock, were subjected to a change in drainage conditions.
Abstract: "It is concluded that the bauxite resulted from the removal of silica and iron by leaching when kaolinitic clays, developed from aluminarich bedrock, were subjected to a change in drainage conditions It is proposed that the bauxite belt of the Guianas represents an old shoreline along which there existed swampy regions, and the suggestion is made that it is the existence together of these swamps with suitable sub-surface material which has resulted in the ultimate formation of the bauxites via an intermediate kaolinitic stage"
TL;DR: In this article, a relatively simple method has been developed to obtain the strike and dip of planar elements intersected in 1 drill hole, which consists of marking the core before it is broken off, and orientating the core relative to the hole axis by means of the mark after it is recovered.
Abstract: A relatively simple method has been developed to obtain the strike and dip of planar elements intersected in 1 drill hole. The method consists of marking the core before it is broken off, and orientating the core relative to the hole axis by means of the mark after it is recovered.