Petrographic variation in the Springfield (No. 9) coal in Western Kentucky

The Springfield (Western Kentucky No. 9) coal of the Carbondale Formation (Middle Pennsylvanian) in the Western Kentucky Coal Field of the Illinois Basin was sampled in eleven mines from one to three channels of three equal benches. The rank of the coal is high-volatile C bituminous in the Moorman Syncline and in the Henderson Basin and high-volatile B bituminous in the Webster Syncline. The percentage of total vitrinite macerals and of total vitrinite plus liptinite was found to decrease significantly from the bottom bench through to the top bench. In a comparison of the sources of variation within the set of maceral data it was found that the only significant variation in the vitrinite and vitrinite plus liptinite percentages was between the benches. Both the rank of the coal and the maceral percentages are varying in a predictable manner.     

Brecciated and mineralized coals in Union County, Western Kentucky coal field

Coals from the D-2 and D-3 boreholes in the Grove Center 7 1/2 min quadrangle, Union County, KY, have been found to be highly brecciated and mineralized. The mineralization is dominated by a carbonate assemblage with minor sulfides and sulfates. Included among the secondary minerals is the lead selenide, clausthalite. Overall, the emplacement of secondary vein minerals was responsible for raising the rank of the coals from the 0.6–0.7% R_max range found in the area to as high as 0.95–0.99% R_max.A 1.3-m-thick coal found in one of the boreholes is unique among known Western Kentucky coals in having less than 50% vitrinite. Semifusinite and fusinite dominate the maceral assemblages. The coal is also low in sulfur coal, which is unusual for the Illinois Basin. It has an ash yield of less than 10%; much of it dominated by pervasive carbonate veining. The age of the thick coal in core D-2 is similar to that of the Elm Lick coal bed, found elsewhere in the Western Kentucky coalfield. The coals in D-3 are younger, having Stephanian palynomorph assemblages.     

Paradise (and Herrin) lost: Marginal depositional settings of the Herrin and Paradise coals, Western Kentucky coalfield

This is the fourth installment in a series of papers on the Asturian (Westphalian D) disrupted mire margins, termed the “ragged edge” in previous papers, and limestone distributions in the Herrin–Baker coal interval in the Western Kentucky extension of the Illinois Basin. New data, indicating in-situ peat development and marine influence, collected from the first in-mine exposure of this interval are presented. Borehole data from the region are examined in the context of “ragged edge” exposures and a carbonate platform depositional model for this portion of the Illinois Basin is presented. This shows that deposition of the sequence was influenced both by the underlying sediments and by a marine transgression. The former influence is seen in variations in coal and limestone thickness over sandstone-filled channels versus over shale bayfill deposits. The latter is marked by the progressive upwards loss of coal benches (i.e., the bottom bench of both coals is the most extensive and the Herrin coal is more extensive than the overlying Paradise coal) and by marine partings in both coals. Further, the brecciated margins seen in both coal seams are similar to brecciated peats encountered along the Everglades margins of Southwest Florida. Overall coal distributions are similar to both those along the Everglades margins and those along a transect from the Belize coast to Ambergis Caye.     

Petrography of the Herrin (No. 11) coal in western Kentucky

The Herrin (No. 11) coal in western Kentucky is in the upper part of the Pennsylvanian (Des Moinesian) Carbondale Formation. Samples were obtained from 13 mines in Kentucky and one mine in Illinois in three equal benches from two to three channels for a total of 93 samples. The rank of the coal (as vitrinite reflectance) is high volatile C bituminous in the Moorman Syncline and high volatile A bituminous in the Webster Syncline. Reflectance does not vary between mines in in the Moorman Syncline. The percentage of total vitrinite macerals for each mine is over 85% and the percentage of togal vitrinite plus liptinite maceralsis over 89% (average over 90%) (both on dry, mineral-free basis). The variation of the two maceral percentages is only significant at the betweenbench level, the middle bench generally having the lowest vitrinite and vitrinite plus liptinite percentages.     

Mineralogy and geochemistry of different morphological pyrite in Late Permian coals,South China

The mineralogical and morphological characteristics, concentration of major and trace elements, and sulfur isotopic composition of three pyrite and two coal samples in the Upper Permian high-sulfur coals from Xingren, Zhijin, and Hefeng mining area, South China, were investigated, by using optical microscopy, field emission-scanning electron microscopy in conjunction with an energy-dispersive X-ray spectrometer (FE SEM-EDS), X-ray powder diffraction (XRD), X-ray fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS), cold vapor atomic absorption spectrometry (CVAAS), and isotopic ratio mass spectrometer. The pyrite in Xingren and Zhijin coals mainly occurs as nodular, lens-shaped, thin-layer, and massive forms, and it occurs mainly as fine vein fillings in the Hefeng coals. Microscopically, pyrite in the coals from Xingren, Zhijin, and Hefeng mainly occurs as framboidal, cell-filling, and vein-filling forms, respectively. There is a distinct difference in X-ray powder diffractogram and diffraction data of the three pyrite samples. There is a maximum diffraction peak (2.709 Å) in pyrite in the coals from Xingren and (2.707 Å) in pyrite in the coals from Zhijin; however, the maximum diffraction peak is 3.343 Å in pyrite in the coals from Hefeng. The average unit cell length (a ₀) is 5.4169 Å for the Xingren pyrite, 5.4159 Å for the Zhijin pyrite, and 5.4170 Å for the Hefeng pyrite. The ratio of S/Fe is 2.16 for the Xingren pyrite, 2.09 for the Zhijin pyrite, and 2.01 for the Hefeng pyrite. Copper (701 μg/g), Ni (369 μg/g), and Co (29.6 μg/g) concentrated in the Hefeng pyrite. The concentration of As is 126, 19.6, and 19.1 μg/g in the Hefeng, Zhijin, and Xingren pyrite, respectively. Mercury is 11.7 μg/g in the Xingren pyrite, 2.79 μg/g in the Zhijin pyrite, and 0.512 μg/g in the Hefeng pyrite. There is a clear tendency that elements Cu, Ni, Co, Cr, Se, Mo, and As are significantly enriched in the Hefeng pyrite. Mercury is greatly enriched in the Xingren pyrite, and Zn is enriched in Zhijin pyrite. Rare earth elements and yttrium (REY) are not abundant (8.276 μg/g) in the Hefeng pyrite and are characterized by maximum positive anomaly of Eu (Eu/Eu* = 6.54). The δ³⁴S value is ?26.9 ‰ in the Xingren pyrite, +3.8 ‰ in the Zhijin pyrite, and +3.7 ‰ in the Hefeng pyrite. The trace elements in the Hefeng pyrite and coal are As (126 and 6.1 μg/g), Hg (0.512 and 0.158 μg/g), Zn (276 and 56.7 μg/g), Se (16.5 and 1.07 μg/g), Mo (45.5 and 9.93 μg/g), Cu (701 and 37.8 μg/g), Ni (369 and 16.9 μg/g), Co (29.6 and 8.63 μg/g), Sb (2.64 and 0.742 μg/g), Cd (3.49 and 0.366 μg/g), and Pb (62.8 and 33.5 μg/g), demonstrating that these potentially toxic trace elements were mainly concentrated in pyrites. The strongly positive Eu anomaly (Eu/Eu* = 6.54) in the netted pyrite vein filled in the cleats of the Hefeng coal may be the product of epigenetic hydrothermal fluid.     

Mineral matter and the nature of pyrite in some high-sulfur tertiary coals of Meghalaya, northeast India

Coal samples collected from four different sources in the Jaintia Hills of Meghalaya, northeast India, have been investigated for their sulfur content, mineral matter, and to assess their potential behavior upon beneficiation. These coals contain high sulfur which occurs both in organic and inorganic forms. The organic sulfur content is much higher than the inorganic sulfur. Studies on different size and gravity fractions indicated that the mineral phases are concentrated in higher density fractions (d > 1.8) and in general are fine grained (<50 μm). Data of reflected-light optical microscope and electron probe micro-analysis (EPMA) revealed that minerals in these coals are sulfides-pyrite, marcasite, sphalerite, pentlandite; sulfates-barite, jarosite; oxides-hematite, rutile; hydroxides-gibbsite, goethite; phosphate-monazite; carbonate-calcite, siderite and silicates-quartz, mica, chlorite, and kaolinitic clay. The disulfides of iron occur in two modes — mainly pyrite and occasionally marcasite with wide size ranges and in various forms, such as: framboid, colloidal precipitate, colloform-banded, fine disseminations, discrete grains, dendritic (feathery), recrystallized, nuggets, discoidal, massive, cavity-fracture- and cleat-fillings. Framboidal pyrite has formed primarily due to biological activities of sulfur reducing bacteria in the early stages of coalification. Massive and other varieties have formed at later stages due to coalescence and recrystallization of the earlier formed pyrites. Sulfur isotopic values indicate a biogenic origin for the pyrites. Association of trace metals, such as Ni, and Zn has been recorded in these pyrites. Given the large fractions of organic sulfur present, these coals can be upgraded only partially to reduce the sulfur content by beneficiation.     

The nature of scattered and concretion pyrite in the Upper Abalak Formation of the Salym oil field (Western Siberia)

Dispersed and concretionary pyrite in chert–clay–carbonate and carbonate rocks of the Abalak Formation (Salym oil field) have been studied. The study was conducted using Scanning Electron Microscopy (SEM), Electron Probe Microanalysis (EPMA), and high spatial resolution Secondary Ion Mass Spectrometry (Nano-SIMS). As a result, three morphological groups of pyrite have been distinguished: large cubic crystals, framboidal pyrite, and fine-crystal aggregates that replace organic remnants. The sulphur isotope ratio allows one to distinguish two genetic types of pyrite. The source of the sulphur for the first genetic group was H₂S produced by bacterial sulphate reduction, while the second group pyrite was formed with sulphur as a product of thermochemical sulphate reduction.     

Magma hybridization in the Western Tatra Mts. granitoid intrusion (S-Poland, Western Carpathians)

In the Variscan Western Tatra granites hybridization phenomena such as mixing and mingling can be observed at the contact of mafic precursors of dioritic composition and more felsic granitic host rocks. The textural evidence of hybridization include: plagioclase?CK-feldspar?Csphene ocelli, hornblende- and biotite-rimmed quartz ocelli, plagioclase with Ca-rich spike zonation, inversely zoned K-feldspar crystals, mafic clots, poikilitic plagioclase and quartz crystals, mixed apatite morphologies, zoned K-feldspar phenocrysts. The apparent pressure range of the magma hybridization event was calculated at 6.1?kbar to 4.6?kbar, while the temperature, calculated by independent methods, is in the range of 810°C?770°C. U-Pb age data of the hybrid rocks were obtained by in-situ LA-MC-ICP-MS analysis of zircon. The oscillatory zoned zircon crystals yield a concordia age of 368?±?8?Ma (MSWD?=?1.1), interpreted as the age of magma hybridization and timing of formation of the magmatic precursors. It is the oldest Variscan magmatic event in that part of the Tatra Mountains.     

Influence of regional structure on the development and quality of the Upper Elkhorn no. 2 coal bed, eastern Kentucky

The Upper Elkhorn No. 2 coal bed (Middle Pennsylvanian Breathitt Formation) in eastern Kentucky exhibits thickness and coal quality trends which suggest that peat deposition was contemporaneous with tectonism. The coal thickens and has high vitrinite and low ash and sulfur content the Belfry anticline in Pike Country. T in the vicinity of the Floyd Country channel, a basement trough. In both cases other Pennsylvanian coals exhibit similar trends, suggesting that the penecontemporaneous tectonism persisted at least through a portion of the Carboniferous.     

Splint coals of the Central Appalachians: Petrographic and geochemical facies of the Peach Orchard No. 3 split coal bed,southern Magoffin County,Kentucky

The Bolsovian (Middle Pennsylvanian) Peach Orchard coal bed is one of the splint coals of the Central Appalachians. Splint coal is a name for the dull, inertinite-rich lithologies typical of coals of the region. The No. 3 Split was sampled at five locations in Magoffin County, Kentucky and analyzed for petrography and major and minor elements. The No. 3 Split coals contain semifusinite-rich lithologies, up to 48% (mineral-free basis) in one case. The nature of the semifusinite varies with position in the coal bed, containing more mineral matter of detrital origin in the uppermost durain. The maceral assemblage of these terminal durains is dominated by detrital fusinite and semifusinite, suggesting reworking of the maceral assemblage coincident with the deposition of the detrital minerals. However, a durain in the middle of the coal bed, while lithologically similar to the uppermost durains, has a degraded, macrinite-rich, texture. The inertinite macerals in the middle durain have less distinct edges than semifusinites in the uppermost terminal durains, suggesting degradation as a possible path to inertinite formation. The uppermost durain has higher ash and semifusinite contents at the eastern sites than at the western sites. The difference in the microscopic petrology indicates that megascopic petrology alone can be a deceptive indicator of depositional environments and that close attention must be paid to the individual macerals and their implications for the depositional setting, especially within the inertinite group.     

Concentration of elements in lacustrine coals from zone A hat creek deposit no. 1, British Columbia,Canada

Coal samples from the 170-m-thick A zone of the Hat Creek coal deposit No. 1 in central British Columbia were examined for major-, minor- and trace-element distribution. The coal is lignite/ subbituminous in rank and of Eocene age. This study shows: (1) As, B, Br, Cl and S are the only elements organically associated in these samples; (2) Concentration of certain elements such as Fe, Mn and Co can be related to the presence or absence of carbonate and/or sulphide minerals; (3) Distribution of certain elements, (i.e. Al, B, Br, Cl, Cr, Fe, Th, U and Zn) follow similar patterns of concentration or depletion across the vertical thickness of Zone A and suggest three depositional cycles; (4) Concentration of boron versus chromium, sodium, sulphur and uranium for these coals clearly placed them in a freshwater environment; (5) Rates of sedimentation using the Na/K ratio also suggest three depositional cycles; (6) In resinite samples, hand-picked from these coals, the concentrations of all elements except As and Se were lower than their concentrations in the whole coals.     

Scandium in the coals of Northern Asia (Siberia,the Russian Far East,Mongolia, and Kazakhstan)

We present new original data on the geochemistry of scandium in the coals of Asian Russia, Mongolia, and Kazakhstan. In general, the studied coals are enriched in Sc as compared with the average coals worldwide. Coal deposits with abnormally high, up to commercial, Sc contents were detected in different parts of the study area. The factors for the accumulation of Sc in coals have been identified. The Sc contents of the coals depend on the petrologic composition of coal basins (composition of rocks in their framing) and the facies conditions of coal accumulation. We have established the redistribution and partial removal of Sc from a coal seam during coal metamorphism. The distribution of Sc in deposits and coal seams indicates the predominantly hydrogenic mechanism of its anomalous concentration in coals and peats. The accumulation of Sc in the coals and peats is attributed to its leaching out of the coal-bearing rocks and redeposition in a coal (peat) layer with groundwater and underground water enriched in organic acids. The enrichment of coals with Sc requires conditions for the formation of Sc-enriched coal-bearing rocks and conditions for its leaching and transport to the coal seam. Such conditions can be found in the present-day peatland systems of West Siberia and, probably, in ancient basins of peat (coal) accumulation.     

Cobalt zoning in microscopic pyrite from Kamoto,Republic of the Congo (Kinshasa)

The Kamoto deposit consists of two stratiform orebodies separated by a barren sedimentary unit. It is a copper and cobalt deposit, the main features of which are summarized in the first part of the paper. Above the upper orebody, dolostone beds are found, where pyrite is the only sulfide mineral. This pyrite was investigated with the help of a microprobe: all idiomorphic grains were found to be surrounded by a well-defined rim, where the cobalt content reaches 4%; framboidal grains were also found to be heterogeneous with respect to cobalt. The distribution of nickel and copper is described. These observations afford one more evidence that post-depositional events played an important role in the Mine Series of Katanga, especially with regard to heavy metals geochemistry.

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Resume Le gisement de Kamoto est constitué de deux corps minéralisés stratiformes séparés par une unité sédimentaire stérile. C'est un gisement de cuivre et de cobalt dont les principales caractéristiques sont brièvement résumées. Audessus du corps minéralisé supérieur, on trouve des couches de dolomie, où la pyrite est le seul sulfure présent. Cette pyrite a été étudiée à l'aide d'une microsonde: tous les grains idiomorphes y sont entourés d'une bordure bien nette, où la teneur en cobalt atteint 4%; les grains d'apparence framboïdale sont également hétérogènes au point de vue de leur teneur en cobalt. La distribution du nickel et du cuivre est décrite. Ces observations apportent um témoignage supplémentaire de l'importance des événements postérieurs au dépôt dans la «Série des Mines» katangaise, tout spécialement en ce qui concerne la géochimie des métaux lourds. Elles démontrent que le «système» constitué par la roche sédimentaire est resté ouvert pendant un certain temps après la sédimentation.