Search

Southeast Asia is replete with Cenozoic sedimentary coal-bearing basins. These basins can be grouped into five regions: northern Sundaland, southern Sundaland, the Philippine archipelago, western Myanmar and eastern Indonesia. Only the first three are discussed in this paper. Each of the three areas has unique coal basin properties as a result of differing tectonic, palaeogeographic, palaeoclimatic and depositional histories. The most significant coal deposits of SE Asia formed in large sedimentary basins within the Neogene in southern Sundaland (the islands of Borneo and Sumatra) over extensive coastal plains, in a regressive setting, and multiple seams of > 5 m thickness are widespread. Locally much thicker seams have developed. Typically, the coal deposits have low ash yield and sulphur contents. In contrast the interior coal deposits of northern Sundaland formed within small disconnected grabens and half grabens, with continental fill, and were not influenced by marine base level changes. The coal deposits are areally restricted. Coal thickness is variable, with one or two main seams, up to 6 to 20 m when well developed, but there are locally much thicker coal-dominated stratigraphic intervals. The ash yields are usually moderate to high and sulphur contents are variable, often high. Coal within the basins of the Philippine archipelago typically has similar coal quality to the coal deposits of southern Sundaland with variable coal rank but the deposits are not extensive, being limited by basin size and structural complexity. Southern Sundaland has had the least change palaeogeographically, residing mainly within ± 10° of the equator. Its palaeoclimate has remained conducive to ever-wet conditions, the climate most favourable for peat formation, throughout the Cenozoic. Northern Sundaland (i.e. SE Asian continental) has consistently resided > 10° north of the equator throughout all of the Cenozoic. The palaeoclimate was therefore tropical but probably monsoonal with significant annual dry periods. These conditions are not the most conducive to peat formation. In contrast to the Sundaland basins, the Philippine archipelago had less tectonic stability and has a complex palaeogeographic history with some regions passing through equatorial areas (and climates) while others were always north of the equator. The tectonic and depositional histories of the three regions are unique and contributed to the character of the resultant coal. Basins in northern Sundaland were most affected by the collision of India with the Asian continent during the Palaeogene. Syn -rift basins formed within continental crust resulting in small, mainly disconnected basins which were filled with coarse but generally fining up sequences containing coal seams and sediments of freshwater lacustrine and fluvial origin. The basins did not develop beyond the syn -rift phase, being constrained by the intra-continental setting and probably the stresses from the India-Eurasia collision. The southern margin of Sundaland also was affected by Palaeogene extension resulting in the development of small syn -rift basins containing a similar initial sequence to northern Sundaland. However, after the initial rifting much larger wider basins formed. This probably reflects major differences in the fundamental crustal architecture and lithosphere between northern and southern Sundaland. The initial syn -rift (and early post-rift) rock units were eventually transgressed by marine sediments. Later basin inversion and mountain uplift in the hinterland provided a sediment source for the deposition of widespread fluvial-deltaic and coastal plain sediments. Areally extensive peat mires then formed, within a regressive sedimentary sequence. The tectonic development of the Philippine archipelago is extremely complex. The archipelago is composed of modern and ancient island arcs and merged continental fragments. Various rifting and amalgamation of micro continental fragments had resulted in a plethora of small coal-bearing basins most of which are dissected and structurally disturbed. Southern Sundaland (i.e. the islands of Sumatra and Borneo) has the most extensive coal deposits in SE Asia. During the Cenozoic the region had the right sequence of tectonic events, palaeogeography, and palaeoclimate. Laterally extensive coal seams developed during the Eocene in southeast and central Kalimantan (Borneo) in an early post-rift setting under conditions of relative marine transgression. By the Middle Miocene the basins of southern Sundaland were experiencing a depositional setting with palaeogeographic and palaeoclimatic conditions that were conducive for the development of widespread and thick ombrogenous peat mires, which resulted in the formation of vitrinite-rich coals with low ash yields and low sulphur contents. The combination of large basins that quickly infilled to base level, an ever-wet climate, and a depositional setting where peat mires could form and be preserved resulted in the formation of areally extensive and thick coal deposits from the Middle Miocene through to the Pliocene. Although there are locally significant coal deposits in northern Sundaland, the depositional setting was within small continental-fill syn -rift grabens, many with a lacustrine environment, in a seasonally drier palaeoclimate than southern Sundaland. Development of peat mires was not areally extensive, and the coal seams have higher ash yields and sulphur contents, and a locally higher content of liptinite macerals. Coal deposits in the Philippine archipelago developed under broadly similar palaeoclimates to southern Sundaland, with a similar range of coal qualities. However, the structural complexity and limited areal extent of many of the coal deposits reflects the tectonic complexity during and after the period of coal formation. [ABSTRACT FROM AUTHOR]

Petrographic, geochemical and carbon isotopic determinations were conducted on five samples from four seams within the Late Cretaceous-Paleocene of the Guaduas Formation in Colombia. The individual coal seams are thin, ranging from 0.59 to 1.2 m, and occur over a 157 m interval. The average weighted ash yield is 13.7% (dry basis), although one sample presented values >35%. Vitrinite reflectance increases from 1.33% in the stratigraphically uppermost seam (La Cuarta) to 1.44% in the lower most coal seam (Cisquera), indicating their rank to be medium volatile bituminous. The studied sequence of the Guaduas Formation represents a peat environment influenced by shifting depositional settings, particularly in relation to the proximity of marine/brackish water environments as indicated by Sr/Ba values, sulfur, pyrite, δ 13C and the proportion of telinite. A decrease in inertinite indicates that the peat mires were becoming relatively 'wetter' stratigraphically upwards. This trend, unlike that of Sr/Ba and telinite, may be driven by climatic shifts rather than only changes in depositional environment. Both trace and rare earth elements, plus yttrium (REY) are related to the inorganic fraction of the coal. All rare earth elements are depleted relative to average worldwide hard coals (for trace elements) and average upper continental crust (for REY) with the notable exception of Li and Sb for the high ash yield sample (the La Cuarta lower coal seam). The abundance of some REY elements (i.e. Eu, Gd, Tb, Dy, Y, Ho, Er, Tm, Yb and Lu) may be more influenced by the presence of illite rather than just the quantity of total ash yield. Based on the relationship between SiO 2 and Nb/Y, the provenance of the inorganics changed from a rhyolitic source at the lowest seam (Cisquera) to a dacite source in the middle layer (El Tesoro) to an andesite source in the stratigraphically uppermost seams (La Gemela and La Cuarta). [Display omitted] • Low inertinite at the top seam may indicate wetter conditions and/or less fire than the lower seams • Strong correlation between Sr/Ba, %telinite and δ13C may be related to the relative proximity to marine/brackish water environments • Both trace elements and REY are depleted relative to world averages but vary directly with ash yield • The upper most seam studied (La Cuarta) demarcates a change from mostly terrestrially influenced to more marine/brackish water influenced environments • The ultimate source of the inorganics changed from rhyolitic to dacite to andesite from the bottom most coal to the top most in this study. [ABSTRACT FROM AUTHOR]

Abstract: To assess the commercial viability of a coalbed methane prospect two of the key geological parameters measured are gas content (desorbed gas) and gas holding capacity (adsorption capacity). These two measures, together with reservoir pressure, give an estimate of the gas saturation of the reservoir. Typically gas saturation has been assessed by collecting one adsorption isotherm sample and assuming it is representative of the whole seam reservoir conditions. This study addresses that assumption. To understand the level of variation, and thus the inherent uncertainty in saturation, one core (Jasper-1) from the Huntly coalfield in New Zealand was analysed in detail. Ten samples (representing the whole coal seam) were placed into gas desorption canisters and desorbed for ten days and then analysed for adsorption capacity. Desorption analyses for total measured gas content (average in-situ basis) ranged from 2.32 to 2.89 m3/t (standard deviation (sd)=0.18) and gas adsorptive capacity at 4 MPa (average in-situ basis) from 2.11 to 3.51 m3/t (sd=0.38) resulting in saturations ranging from 66% to 120% (sd=15). Determination of how many samples are required to make a realistic assessment of average reservoir properties requires a consideration of: (i) the level of accuracy desired, (ii) the limit of accuracy possible, which is governed by the magnitude of experimental error, and (iii) the innate variability of the seam. It was found that a minimum of five samples each for adsorption and desorption were required in order to significantly decrease the uncertainty in gas saturation estimates for a subbituminous coal. [Copyright &y& Elsevier]

Abstract: The Huntly coalfield has significant coal deposits that contain biogenically-sourced methane. The coals are subbituminous in rank and Eocene in age and have been previously characterised with relatively low to moderate measured gas (CH4) contents (2–4 m3/ton). The CO2 holding capacity is relatively high (18.0 m3/ton) compared with that of CH4 (2.6 m3/ton) and N2 (0.7 m3/ton) at the same pressure (4 MPa; all as received basis). The geothermal gradient is also quite high at 55 °C/km. A study has been conducted which simulates enhancement of methane recovery (ECBM) from these deposits using a new version of the TOUGH2 (version 2) reservoir simulator (ECBM-TOUGH2) that can handle non-isothermal, multi-phase flows of mixtures of water, CH4, CO2 and N2. The initial phase of the simulation is CH4 production for the first 5 years of the field history. The model indicates that methane production can be significantly improved (from less than 80% recovery to nearly 90%) through injection of CO2. However, although an increase in the rate of CO2 injection increases the amount of CO2 sequestered, the methane recovery (because of earlier breakthrough with increasing injection rate) decreases. Modeling of pure N2 injection produced little enhanced CH4 production. The injection of a hypothetical flue gas mixture (CO2 and N2) also produced little increase in CH4 production. This is related to the low adsorption capacity of the Huntly coal to N2 which results in almost instantaneous breakthrough into the production well. [Copyright &y& Elsevier]

[Display omitted] • The No. 4 Coal was deposited in a relatively oxygen-rich environment. • The No.4 Coal seam was subjected to multiple stages of solutions. • Distributions of Ba and Sr display a fan-shaped trend in the Binchang mining area. • Barite and celestine in the coal are closely related to carbonate minerals. • Highly elevated Ba and Sr are the results of solutions leaching of barite deposits. The Middle Jurassic coal seams located in the southern Ordos Basin display notably high concentrations of barium (Ba) and strontium (Sr). To acquire a comprehensive understanding of the source and occurrence of the elevated contents of Ba- and Sr-bearing minerals and their formation mechanism in the coal, a suite of petrological, mineralogical, and geochemical analyses was conducted on the Middle Jurassic coals of the Gaojiapu mine (No. 4 Coal) from the Binchang mining area, using optical microscopy, field emission-scanning electron microscopy, X-ray diffraction, X-ray fluorescence, and inductively coupled plasma mass spectrometry. The results indicate that the No. 4 Coal is a high volatile B bituminous coal, which is characterized by low ash, medium sulfur, and high inertinite contents. The modes of occurrence of minerals identified in the coal, including calcite, dolomite, pyrite, quartz, kaolinite, anatase, barite, and celestine, indicate that the No. 4 Coal may have been subjected to multiple stages of solutions injection. Barium and Sr in the investigated coals are significantly enriched, exhibiting maximum values of 19738 μg/g and 9932 μg/g, respectively, while concentrations of other trace elements are generally depleted. Barite and celestine, generally coexisting with carbonate minerals, commonly occur as cell- and fracture-fillings. Furthermore, the strong correlation coefficients (r) for Ba vs. Ca + Mg and Sr vs. Ca + Mg (0.78 and 0.61, respectively) indicate that most barite and celestine have a close association with carbonate minerals of epigenetic origin. The highly elevated concentrations of Ba and Sr are thought to be primarily derived from solutions leaching barite deposits developed in the Qinling Orogenic Belt, which is located in the south of the Ordos Basin. When mapped spatially, the distributions of Ba and Sr concentrations are fan-shaped, decreasing from the NW to the SE of the mining area. Meteoric water containing dissolved CO 2 induced partial dissolution of carbonate rocks, and during this process, selected metal ions (e.g., Ca2+, Mg2+, Al3+, Si2+, Fe2+, Ba2+, and Sr2+) were redistributed and subsequently migrated along fracture zones to the coal seam. The fracture systems and abundant cavities within inertinite in the coal provided sufficient space and conduits for solutions migration. [ABSTRACT FROM AUTHOR]

Prospecting for trace and rare earth elements will only increase in the coming decades as the world expands into sustainable energy and the use of digital technology. A key component of finding these resources is understanding how they are distributed, mobilized and emplaced. The coal beds in Shanxi Province in China have already been identified as a resource with elevated trace elements, especially lithium. This study has extended the understanding of trace elements in the region from examination of two sites, one in the Ningwu coalfield (the No. 11 coal seam) and the other in the Qinshui Basin (the No. 8 coal seam). Lithium, in particular, but most trace elements, in general, were found to be associated with the inorganic fraction of the coal seams. Specifically, trace elements are highest in the sediments overlying the coal and in the interbedded partings. The coal beds themselves were also enriched, especially in Li, but their concentrations vary in direct proportion with ash yield. Differing degrees of maturation (the Ningwu site ~0.70% Ro; the Qinshui site ~2.50% Ro) seem to have little effect on the association of trace elements with inorganics. Using the relationship between Rb vs Y + Nb, the ultimate provenance of the sediment (and thus the trace elements) may be from the weathering products of regionally proximal granites. However, two high ash coal outliers, both from the Qinshui Basin sampling site, appear to have a different trace element source, as yet unidentified, compared to all other samples. The REY (rare earth elements and Y) patterns indicate hydrothermal fluids are also responsible for REY enrichments in the coal seams. • High Li-coals of two sites in Shanxi Province in China were presented. • Differing degrees of maturation seem to have little affect on the association of trace elements with inorganics. • The relationship between Rb vs Y + Nb was employed to distinguish the provenance of the sediment. [ABSTRACT FROM AUTHOR]

Abstract: Small angle scattering techniques (SAXS and SANS) have been used to investigate the microstructural properties of the subbituminous coals (R max 0.42–0.45%) from the Huntly Coalfield, New Zealand. Samples were collected from the two thick (>5 m) coal seams in the coalfield and have been analysed for methane and carbon dioxide sorption capacity, petrography, pore size distribution, specific surface area and porosity. Specific surface area (SSA) available for carbon dioxide adsorption, extrapolated to a probe size of 4 Å, ranged from 1.25×106 cm−1 to 4.26×106 cm−1 with total porosity varying from 16% to 25%. Porosity was found to be predominantly composed of microporosity, which contributed the majority of the available SSA. Although considerable variation was seen between samples, the results fit well with published rank trends. Gas holding capacity at the reservoir pressure (approximately 4 MPa) ranged from 2.63 to 4.18 m3/t for methane on a dry, ash-free basis (daf) and from 22.00 to 23.72 m3/t daf for carbon dioxide. The resulting ratio of CO2:CH4 ranged from 5.7 to 8.6, with an average of 6.7:1. Holding capacities for both methane and carbon dioxide on a dry ash free basis (daf) were found to be correlated with sample microporosity. However, holding capacities for the two gases on an as analysed (aa) basis (that is including mineral matter and moisture), showed no such correlation. Carbon dioxide (aa) does show a negative correlation with both specific surface area and microporosity. As the coals have low inorganic matter content, the reversal is thought to be related to moisture which is likely concentrated in the pore size range 12.5–125 Å. Methane holding capacity, both daf and aa, correlates with macroporosity, thus suggesting that the holding capacity of micropores is diminished by the presence of moisture in the pores. [Copyright &y& Elsevier]

The high frequency of fires during the formation of some mire systems in the Jurassic is thought to have influenced how terrestrial ecosystems evolved. Ancient mires, now present as coal seams, contain high-resolution paleoenvironmental and paleoclimatic records. Thus, the analysis of coal beds provides valuable, insightful, and practical knowledge on the changes in paleoclimate and, in this case, fire prevalence. Using petrographic, carbon isotopic, mercury content, and polycyclic aromatic hydrocarbon (PAH) determinations, the Middle Jurassic No. 4 coal from the Binchang region in the Ordos Basin was examined in order to understand the nature of fire during the formation of the mires. The results show that the No. 4 coal exhibits a high content of inertinite (average content 70%). Notably, the correlation coefficient (r = 0.79) between the concentration of PAHs (with >3 rings) and the proportion of inertinite indicates that the high content of inertinite was predominantly the result of fire. The presence of natural char and coke in the coals further indicates the frequent incidence of fires during the Middle Jurassic in the southern Ordos Basin. High frequency of fires can be attributed to the availability of fuel (i.e., the buildup of organic material), high atmospheric oxygen levels, and intermittent dry climatic conditions. The random reflectance of inertinite (specifically, fusinite and semifusinite) in the No. 4 coal bed ranges from 1.25% to 2.45%, which, with the presence of pyrogenic PAHs, suggests that their formation may have been predominantly affected by low- and moderate-temperature fires. The high frequency of fires is thought to have significant impacts on terrestrial and hydrological ecosystems. These effects may have included the circulation of atmospheric mercury, as well as the possible occurrence of anoxic events in the lakes. • Pyrogenic PAHs and inertinite in coals indicate the occurrence of Jurassic fires. • High p O 2 level and relatively arid climate promote the occurrence of fires. • The negative excursion of δ 13C in the coals may be the result of fire activities. • Anomalies of mercury in the coals are associated with the temperature by fires. • The runoff post-fire may promote the occurrence of lake hypoxia events. [ABSTRACT FROM AUTHOR]

Igneous intrusions into coal affect the safety, productivity, and economic viability of many coal mines. Also, the alterations in coal caused by igneous intrusions encompass a deterioration in coal quality, a decrease in permeability, an enhancement of coal rank, and geochemical and mineralogical compositions. Although there have been some studies related to the effects of igneous intrusions on the inorganic constituents in the coal, the mechanism of newly formed chemical and mineralogical associations caused by igneous intrusions has not been fully understood. This paper investigates the mineralogical and geochemical responses of coal to thermal alteration by igneous intrusion into an Early Permian coal seam in Hebei Province, North China. The Fengfeng coalfield is structurally complex, experiencing variable rates of burial and uplift, with abundant intrusions during the upper Jurassic and maximum burial in the Cretaceous resulting in an increase in rank to the north. In the search for critical minerals and elements, intrusions and hydrothermal alteration are often cited as the source for elevated concentrations. Towards the intrusion, the coal rank indicators increase from semi-anthracite to anthracite over a 500-cm distance, as does the mineral matter. The clay minerals present in coals include NH 4 -illite, kaolinite, paragonite, and chlorite (chamosite and cookeite), which were all resulted from igneous intrusions. The epigenetic minerals mainly include quartz, ankerite, calcite, pyrite, and apatite, which were derived from fluids permeating into the coal seam and chemically interacting with the original minerals or precipitating directly to form new minerals. Geochemical indicators in this coal indicate hydrothermal solutions derived from igneous intrusion. The enrichment of Li and Hg is linked to the igneous activity, potentially influencing the utilization of the coal adjacent to the intrusions. However, the concentrations of the remaining elements in the coal closest to the intrusion show no significant changes, thereby supporting the notion of a "non-universal effect" of igneous intrusions on the elemental composition and concentrations. • Towards the intrusion, the coal rank indicators increase, as does mineral matter. • Various clay minerals in coal are associated with hydrothermal fluids. • Epigenetic minerals show at least three stages of hydrothermal fluids. • Geochemical indicators are used to characterize hydrothermal fluids from intrusion. • The enrichment of Li and Hg in coal nearby intrusion is linked to igneous activity. [ABSTRACT FROM AUTHOR]

Miocene coal beds in the Siniy Utyes Basin, South Primirye, in eastern Russia, are interbedded with volcanic ash layers and are enriched in rare earth elements and Y (REY, or REE if Y is not included), Zr, redox-sensitive and other trace elements around these layers. However, high contents of fresh volcanic glass and alkalies as well as no evidence of leaching suggest that the source of these elevated concentrations of these elements are not interpreted to be derived from the volcanic ash fall layers, as is found in many other coals worldwide. In contrast, the broader geochemical signature of the coal indicates that these elements sourced from weathered granites. Interestingly, both the coal and volcanic ash contain pyrite and, less commonly, barite, REE phosphate (rhabdophane?), silver sulfate and sylvite, all of which indicate a post-depositional emplacement of these trace elements, possibly through an initial evaporative process in the peat before burial. Instead of leaching of the adjacent tuff, enrichment of REY, Zr, Mo, V, and other elements in the coal proximal to the volcanic ash layers may be a result of higher permeability and a geochemical barrier at the coal/volcanic ash interface, which concentrated element migration in these zones during diagenesis. U-Pb zircon dating (LA ICP-MS) of the volcanic ash layer indicates an age in the 18–25 Ma range. The younger (5 of 22 grains) cluster of dates, however, is in the 18–19 Ma (early Miocene) range, which may indicate the age of the actual eruption. [ABSTRACT FROM AUTHOR]

• Petrology, δ13C and gypsum of coal corroborate alternating dry and wet periods. • The fine-scale variability in the δ13C signature was controlled by plant type. • δ13C values positively correlated with angiosperm/gymnosperm and % gypsum. • A high δ13C spike caps each of the four longer-term cycles of peat deposition. • The atmosphere had a significant influence on the peat formation in the basin. Coal contains detailed long-term records of contemporaneous environment, climate, and subsequent diagenetic processes. Stable isotopes of carbon, petrological, palynological, and mineralogical analyses were carried out on a 28 m thick low-rank Miocene coal seam from the Mile Basin, Yunnan Province, China for the purpose of deciphering the palaeoclimate and sedimentary conditions during peat deposition. The coal is characterized by both pale and dark lithotypes. Palynological analyses show that both lithotypes are dominated by angiosperms, which is interpreted to indicate a moderately warm climate. The absence of Fagus and Taxodiaceae pollen suggests that there may have been dry periods during peat accumulation; in general, both Fagus and Taxodiaceae require a constant wet environment in order to proliferate. Organic petrography, δ13C, and gypsum concentrations corroborate that there were alternating drier and wetter periods within the palaeomire during peat accumulation. The fine-scale variability in the δ13C signature appears to be controlled by plant type. Angiosperm/gymnosperm ratios and Vegetation Index are directly correlated with δ13C isotopic values. Plant type, however, seems to be proximally controlled by water level. Angiosperms were more dominant during times of lower water table or less moist conditions, interpreted to correspond to less negative values of δ13C. The correlation of greater concentrations of gypsum with less negative δ13C values also supports drier conditions. However, in addition to the fine-scale variability, four larger scale cycles are defined based on less negative δ13C values. A less negative δ13C isotopic signature demarcates the top of each of these cycles, which represent spikes of lower water table and/or drier conditions. In addition, a general correlation of the δ13C variations in the studied coal seam with atmospheric CO 2 suggests that the atmosphere also had a significant influence on peat formation in the Mile Basin. Although the Mile Basin palaeomire accumulated over a long time, an integrated approach to its analysis has demonstrated considerable variation in palaeoclimate. Changes in wetness/dryness had a direct effect on the ecological composition of the palaeomire. These floral changes would not have only been restricted to the palaeomire but most likely had a regional influence. Thus, detailed analysis of coals can yield useful, insightful and practical knowledge on past regional palaeoenvironmental conditions, which can then be placed within a global context. [ABSTRACT FROM AUTHOR]

Peat depositional environments, the sites where and conditions under which peat accumulates, significantly influence a resultant coal's physical properties, chemical composition, and coal utilization behavior. Recognition of peat depositional environments for coal is a challenging endeavor because coal's observed compositional properties not only result from a variety of geological processes operating during peat accumulation, but also reflect the influence of adjoining or external depositional sedimentary environments and alteration during later diagenesis and/or epigenesis. The maceral or microlithotype composition of any one layer of peat can be the product of years or decades of plant growth, death, decay, and post-burial infiltration by roots in addition to the symbiotic, mutualistic, parasitic, and saprophytic relationships with non-plant biota, such as arthropods, fungi, and bacteria. The overprint of increasing thermal maturation and fluid migration through time on the resulting coal can make these relationships difficult to recognize. Therefore, published models based on maceral composition alone must be used with great caution. Lipid compositions, even from lipid-poor low-rank coals, can provide important information about depositional environments and paleoclimate, especially if combined with the results of organic petrography and paleontological studies. Just as sulfur derived from seawater provides environmental clues, the ratios of two particularly relevant trace elements rather than a single trace element can be used to interpret peat depositional environments. Epigenetic minerals, as well as their corresponding chemical compositions should not be used for such a purpose; similarly, resistant terrigenous minerals deposited during peat accumulation in many cases should be used with considerable caution. The interactions of the biota present in the peat-forming ecosystem, often determined using palynological and geochemical proxies, and their interpretation in the context of geography and paleoclimate are important means for deciphering peat depositional environments. Overall, a combination of evidence from geochemistry, mineralogy, palynology, and petrology of coal and from stratigraphy, sedimentology, and sedimentary facies of related rocks is necessary for accurate and comprehensive determination of depositional environments. The need for interdisciplinary studies is underscored by peat compositional properties, which have been greatly affected by various processes during the syngenetic, diagenetic or epigenetic stages of coal formation. [ABSTRACT FROM AUTHOR]