Coal-forming Plants Research Articles

Geochemistry and Origin of Lead and Selenium in the No. 6 Coal from the Junger Coalfield, North China

The concentration, occurrence, and geological origin of lead and selenium in the main minable coal seam (No. 6 Coal) from the Junger Coalfield were studied using inductively coupled-plasma mass spectrometry, instrumental neutron activation analysis, scanning electron microscope equipped with an energy-dispersive X-ray spectrometer, and optical microscope. The results show that the average concentrations of Pb and Se in the No. 6 Coal are as high as 35.7 μg/g and 8.2 μg/g, respectively, which are much higher than those of coals from North China, Guizhou of China, China, and USA. In addition, their enrichment factors are up to 2.4 and 68.1, respectively. Lead and selenium mainly occur in galena, clausthalite, and selenio-galena. These minerals occur as cell-fillings of coal-forming plants and are of chemical sedimentary origin. Much attention should be paid to the industrial values of high Se in this coal.

Rare earth element distribution in the acetic acid soluble fraction of combusted coals: Its implication as a proxy for the original coal-forming plants

The precise concentrations of rare earth elements (REEs) in Japanese Ashibetsu and Taiheiyo coals, in Indonesian Ambalut coal, and in Australian boghead coal have been determined, in order to compare the REE contents of the coals with those of plants and also to obtain further knowledge of the original plants from which these coals were formed. By leaching the coals after ashing using a 10% acetic acid solution, each coal sample was separated into two fractions: an acetic acid soluble fraction, and an acetic acid insoluble fraction. Our results show that three different types of chondrite-normalized REE patterns are observed in the acetic acid soluble fraction of these coals. The acetic acid soluble fractions of the Ashibetsu, the Taiheiyo, and some of the Ambalut coals showed REE patterns identical to those of peat vegetation. Those of other Ambalut coals showed an REE pattern that was similar to that of tree trunks. The boghead coal showed a different REE pattern that was similar to algae, an origin that is also suggested from a maceral study. The REE patterns of the acetic acid soluble fraction can therefore be a useful proxy for determining the original plants that formed the coals.

Diagenetic quartz and amorphous silica in New Zealand coals

New Zealand coal seams (Late Cretaceous-Miocene, lignite-semi-anthracite) contain numerous and varied occurrences of diagenetic quartz and amorphous silica. Early diagenetic silicifications include: sub-horizontal and laterally extensive, quartz-mineralized bands; micro- and megascopic, euhedral quartz crystals, dispersed or concentrated in layers; and silicified in situ tree stumps. Late diagenetic forms include: sub-horizontal, quartz-mineralized bands, mostly < 1 m in length; and fracture-infillings. The origins of the silica remain uncertain but leached basement rocks and coal measure sediments, and siliceous phytoliths within the coal-forming plants, are possible sources. The silicification of coal seams may have significant implications for exploration, mining and geological studies.

Coal-forming peat plants and some associated floras, Devonian to Tertiary, North America

Coal-forming peat plants and some associated floras, Devonian to Tertiary, North America

Distribution of the Coal Fields and Coal-forming Plants in the World

SYNOPSIS: -For the formation of coal deposits certain conditions in which the sediments including plant remains accumulated are first necessary; they are essen-tially the development of the coal basin and suffiicient supply of plant materials. Subsi-dence of the basin and climate adequate for plant growth might be ultimately influenced by tectonic control through the ages. Throughout the world coals occur in scattered localities in each of the major post-Silurian stratigraphic subdivisions. The distribution of the coal fields is discussed in the relation with tectonic parts of the earth crust.The coal fields of the world are grouped into three types: the orogen (marginal sinking and interior deep), shelf (stabile and labile shelves) and kratogen (marginal district and interior trough) types. The coal fields of each type are also characterized by sedimentary facies, coal reserves and geologic structures. Our knowledge of coal-forming plants is obtained mainly from plant fossils found in the strata above and below the coal seams, and partly from coal and coal balls. On the basis of these sufficient informations the vicissitude of the past forests was first summarized. The considerable formation of workable coal seams in the world corresponds to the flourishment of land plants in the past. Some problems concerning the coal-forming plants of Late Paleozoic and Tertiary coals are discussed.

THE ROWHURST TONSTEIN, NORTH STAFFORDSHIRE, AND THE OCCURRENCE OF CRANDALLITE

Summary The Rowhurst Tonstein occurs in a split of the Rowhurst Coal (Middle Coal Measures) at Red Street Colliery near Kidsgrove, north Staffordshire, the two probably being equivalent to the High Main Tonstein and High Main Coal of Derbyshire. The Rowhurst Tonstein consists of crypto- to micro-crystalline crandallite (mean refractive index 1.624), kaolinite, carbonaceous material, minor apatite, pyrite, quartz and illite. X-ray powder data were obtained from diffractometer traces of the crandallite, and unit cell dimensions ( a 7.007 ± 0.003 Å, c 16.30 ± 0.05 Å) from the spacings d 224̄0 and d 101̄7 respectively. The mineral parageneses are indeterminable, but it seems likely that apatite, kaolinite and the crandallite were co-precipitated from soil colloids derived from peaty, coal-forming plants.

The geochemistry of some British carboniferous sediments

Analyses for major, minor and trace constituents have been made on a series of mudstones, seat earth and coal seam forming part of a Coal Measure succession encountered in an underground borehole at Bersham, North Wales. The mineralogy of the rocks is comparatively simple, quartz, illite and kaolinite being the principal components, with lesser amounts of chlorite, organic matter, sulphide and siderite. From the major element chemistry it is deduced that the oxidation potential of the interstitial waters of the sediments was approximately −0.2 to −0.3 volts during the accumulation of the lower mudstones, but rose during the accumulation of the upper mudstones only to fall again during the accumulation of the upper part of the seat earth and the coal seam. The pH of the interstitial waters may have risen slightly during the accumulation of the upper mudstones but fell again during the accumulation of the seat earth and coal seam. Substantial proportions of the trace element contents of the mudstones were probably already contained in the detrital material arriving at the site of sedimentation, but at some levels they have been significantly augmented by sorption from solution. Under the deduced physico-chemical conditions of sedimentation sorption is the principal process whereby such elements are incorporated into sediments from solution. For certain elements, e.g. B, possibly Ga, the form of sorption is cation exchange, for others, e.g. Rb, Pb it is absorption and for others initial adsorption may be followed by the migration of the elements into more stable lattice sites, e.g.V. The principal sorbents in these rocks are illite and organic matter with colloidal iron monosulphide playing a less significant role. Precipitation may account for the removal of small amounts of such elements as Ni and Mn from solution. The trace element data does not suggest there was any significant change in the salinity of the waters during the accumulation of the rocks studied. The geochemical data does not support the hypothesis that the seat earth represents a leached horizon and this deposit is interpreted as the product of slow sedimentation of intensely chemically weathered material in waters of progressively increasing acidity. The only elements likely to have been accumulated by the coal-forming plants are Co, Ni and Mo. The contents of other trace elements in the ashes of the coal samples can be explained by a continuation of the processes which determined the contents of these elements in the underlying rocks.