Coalification of organic matter in coal balls of the Pennsylvanian (upper Carboniferous) of the Illinois Basin, United States

An evaluation was made of the degree of coalification of two coal balls from the Illinois Basin of the Pennsylvanian (upper Carboniferous) of the United States. Previous interpretations are mainly misleading and contradictory, primarily because of the assumption that the brown color and exceptional cellular and subcellular preservation typical of American coal balls imply chemical preservation of cellulose and lignin, the primary components of peat. Xylem tissue from a medullosan seed fern contained in a coal ball and the coal attached to the coal ball from the Calhoun coal bed, Mattoon Formation, Illinois, was analyzed by elemental, petrographic, and nuclear magnetic resonance (NMR) techniques to determine the degree of coalification. The NMR and elemental data indicate the lack of cellulose and lignin and a probable rank of high-volatile C bituminous coal. These data corroborate data for a coal ball from the Herrin (No. 6) coal bed (Carbondale Formation, Middle Pennsylvanian) and support our hypothesis that the organic matter in coal balls of the Pennsylvanian strata of the United States is coalified to about the same degree as the surrounding coal. Data presented show a range of lower reflectances for xylem tissue and vitrinite in the analyzed coal balls compared with vitrinite in the attached coal.The data reported indicate that physical preservation of organic matter in coal balls does not imply chemical preservation. Also our study supports the hypothesis that compactional (static load) pressure is not a prerequisite for coalification up to a rank of high-volatile C bituminous coal.A whole-rock analysis of the Calhoun coal ball indicates a similarity to other carbonate coal balls from the United States. It consists primarily of calcium carbonate and 1–2% organic matter; silica and alumina together make up less than 0.5%, indicating the lack of minerals such as quartz and clays.     

Resin rodlets in shale and coal (Lower Cretaceous), Baltimore Canyon Trough

Rodlets, occurring in shale and coal (uppermost Berriasian to middle Aptian, Lower Cretaceous), were identified from drill cuttings taken from depths between 9330 ft (2844 m) and 11, 460 ft (3493 m) in the Texaco et al., Federal Block 598, No. 2 well, in the Baltimore Canyon Trough. Under the binocular microscope, most of the rodlets appear black, but a few are reddish brown, or brownish and translucent on thin edges. They range in diameter from about 0.4 to 1.7 mm and are commonly flattened. The rodlets break with a conchoidal fracture, and some show an apparent cellular cast on their longitudinal surfaces. When polished and viewed in reflected light, the rodlets appear dark gray and have an average random reflectance of less than 0.1% whereas mean maximum reflectances are 0.48–0.55% for vitrinite in the associated shale and coal. These vitrinite reflectances indicate either subbituminous A or high-volatile C bituminous coal. The rodlets fluoresce dull gray yellow to dull yellow. The scanning electron microscope (SEM) and light microscope reveal the presence of swirl-like features in the rodlet interiors. Minerals associated with the rodlets occur as sand-size grains attached to the outer surface, as finely disseminated interior grains, and as fracture fillings. Electron microprobe and SEM-energy-dispersive X-ray (EDX) anlayses indicate that the minerals are dominantly clays (probably illite and chlorite) and iron disulfide; calcium carbonate, silicon dioxide, potassium aluminum silicate (feldspar), titanium dioxide, zinc sulfide, and iron sulfate minerals have been also identified. The rodlets were analyzed directly for C, H, N, O, and total S and are interpreted as true resins on the basis of C and H contents that range from 75.6 to 80.3 and from 7.4 to 8.7 wt. % (dry, ash-free basis), respectively. Elemental and infrared data support a composition similar to that of resinite from bituminous coal. Elements determined to be organically associated in the rodlets include S (0.2–0.5 wt.%), Cl (0.03–0.1 wt.%), and Si (0.05–0.08 wt.%). The ash content of the resin rodlets ranges from 4 to 24 wt.% and averages 12 wt.%. Total sulfur contents range from 1.7 to 3.6 wt.%. Resins of fossil plants are known to have little or no sulfur and ash; therefore, these data and the presence of minerals in fractures indicate that most of the sulfur and mineral matter were introduced into the resin partly or wholly after the time of brittle fracture of the resin. The probable source of the resin rodlets is fossil pinaceous conifer cones, which are known to have resin canals as much as 2400 μm in diameter.     

Dissolved organic carbon in pore waters from a hypersaline environment

Pore waters were collected from a sea-marginal, hypersaline pond in the Sinai and analyzed for dissolved organic carbon (DOC). The pore water DOC values ranged from 121 to 818 mg 1⁻¹ with maxima between 15 and 54 cm deep. These values are some of the highest observed from recent sediments and probably reflect production via abiotic as well as biotic sources.     

The Geochemistry of Supraglacial Streams of Canada Glacier,Taylor Valley (Antarctica), and their Evolution into Proglacial Waters

We have investigated the geochemistry of supraglacial streams on the Canada Glacier, Taylor Valley, Antarctica during the 2001–2002 austral summer. Canada Glacier supraglacial streams represent the link between primary precipitation (i.e. glacier snow) and proglacial Lake Hoare. Canada Glacier supraglacial stream geochemistry is intermediate between glacier snow and proglacial stream geochemistry with average concentrations of 49.1 μeq L⁻¹ Ca2+, 19.9 μeq L⁻¹ SO₄²⁻, and 34.3 μeq L⁻¹ HCO₃⁻. Predominant west to east winds lead to a redistribution of readily soluble salts onto the glacier surface, which is reflected in the geochemistry of the supraglacial streams. Western Canada Glacier supraglacial streams have average SO₄²⁻:HCO₃⁻ equivalent ratios of 1.0, while eastern supraglacial streams average 0.5, suggesting more sulfate salts reach and dissolve in the western supraglacial streams. A graph of HCO₃⁻ versus Ca2+ for western and eastern supraglacial streams had slopes of 0.87 and 0.72, respectively with R2 values of 0.84 and 0.83. Low concentrations of reactive silicate (> 10 μmol L⁻¹) in the supraglacial streams suggested that little to no silicate weathering occurred on the glacier surface with the exception of cryoconite holes (1000 μmol L⁻¹). Therefore, the major geochemical weathering process occurring in the supraglacial streams is believed to be calcite dissolution. Proglacial stream, Anderson Creek, contains higher concentrations of major ions than supraglacial streams containing 5 times the Ca²⁺ and 10 times the SO₄²⁻. Canada Glacier proglacial streams also contain higher concentrations (16.6–30.6 μeq L⁻¹) of reactive silicate than supraglacial streams. This suggests that the controls on glacier meltwater geochemistry switch from calcite and gypsum dissolution to both salt dissolution and silicate mineral weathering as the glacier meltwater evolves. Our chemical mass balance calculations indicate that of the total discharge into Lake Hoare, the final recipient of Canada Glacier meltwater, 81.9% is from direct glacier runoff and 19.1% is from proglacial Andersen Creek. Although during a typical, low melt ablation season Andersen Creek contributes over 40% of the water added to Lake Hoare, its overall chemical importance is diluted by the direct inputs from Canada Glacier during high flow years. Decadal warming events, such as the 2001–2002 austral summer produce supraglacial streams that are a major source of water to Lake Hoare.     

Selected elements in major minerals from bituminous coal as determined by INAA: implications for removing environmentally sensitive elements from coal

The four most abundant minerals generally found in Euramerican bituminous coals are quartz, kaolinite, illite and pyrite. These four minerals were isolated by density separation and handpicking from bituminous coal samples collected in the Ruhr Basin, Germany and the Appalachian basin, U.S.A. Trace-element concentrations of relatively pure ( 99⁺%) separates of major minerals from these coals were determined directly by using instrumental neutron activation analysis (INAA). As expected, quartz contributes little to the trace-element mass balance. Illite generally has higher trace-element concentrations than kaolinite, but, for the concentrates analyzed in this study, Hf, Ta, W, Th and U are in lower concentrations in illite than in kaolinite. Pyrite has higher concentrations of chalcophile elements (e.g., As and Se) and is considerably lower in lithophile elements as compared to kaolinite and illite. Our study provides a direct and sensitive method of determining trace-element relationships with minerals in coal.Mass-balance calculations suggest that the trace-element content of coal can be explained mainly by three major minerals: pyrite, kaolinite and illite. This conclusion indicates that the size and textural relationships of these major coal minerals may be a more important consideration as to whether coal cleaning can effectively remove the most environmentally sensitive trace elements in coal than what trace minerals are present.