Tissue Preservation Index Research Articles

Structural analysis of fossilized tree trunks from the Miocene Mydlovary Formation of the South Bohemian Basin (Czech Republic)

Tree trunks were found in situ in Miocene strata of the Mydlovary Formation of the South Bohemian Basin. Our study presents microscopic and chemical tissue analyses of these tree trunks. The trees were fossilized and flattened. However, they are well preserved, which made the analyses feasible. Good preservation of the tissues is indicated by the high Tissue Preservation Index, the high content of cellulose, and the slightly gelified state of the wood. The Gelification Index indicated that there was only limited alteration during diagenesis. Huminite macerals prevailed over liptinite and inertinite macerals, and two varieties of ulminite and textinite were distinguished, differing in colour reflection, light fluorescence, and reflectance values. The biomarker composition in the extracts of the fossil wood obtained by gas chromatography-mass spectrometry, included terpenoid signatures, supporting a relationship to the Family Cupressaceae s.s.. Gradual burial of the trees is indicated by the fact that they lay crosswise on top of each other. The character of the sedimentary environment and the physiological differences of the trees could explain the deformation and the high degree of preservation.

Occurrence and Favorable Enrichment Environment of Lithium in Gaoping Coal Measures: Evidence from Mineralogy and Geochemistry

The Carboniferous-Permian coal measure strata in the Qinshui Basin exhibit highly lithium (Li) enrichment, with substantial exploitation potential. To further explore the enrichment mechanism of lithium in coal measure strata, the No. 15 coal of the Taiyuan Formation from the Gaoping mine is taken as the research object, and its mineralogical and geochemistry characteristics are evaluated using optical microscopy, X-ray diffraction, scanning electron microscopy, inductively coupled plasma mass spectrometry, X-ray fluorescence, and infrared spectral. The results show that the No. 15 coal is semi-anthracite coal with low moisture, low ash, low volatility, and high sulfur. Organic macerals are primarily vitrinite, followed by inertinite, and liptinite is rare; the inorganic macerals (ash) are dominated by clay minerals (predominantly kaolinite, cookeite, illite, and NH4-illite), calcite, pyrite, quartz, siderite, gypsum, and zircon. The average Li content in the coal is 66.59 μg/g, with higher content in the coal parting (566.00 μg/g) and floor (396.00 μg/g). Lithium in coal occurs primarily in kaolinite, illite, cookeite, and is closely related to titanium-bearing minerals. In addition, Li in organic maceral may occur in liptinite. The No. 15 coal was formed in the coastal depositional system, and the deposition palaeoenvironment is primarily a wet–shallow water covered environment in open swamp facies; the plant tissue preservation index is poor, and aquatic or herbaceous plants dominate the plant type. The reducing environment with more terrestrial detritus, an arid climate, and strong hydrodynamic effects is favorable for Li enrichment in coal. The results have important theoretical significance for exploring the enrichment and metallogenic mechanisms of Li in coal.

Paleovegetation and environment during deposition of the Late Oligocene sub-bituminous coal in the Bobov Dol Basin (SW Bulgaria) as deduced from petrographic and geochemical characteristics

Coal and carbonaceous shale samples were taken from the Late Oligocene Bobov Dol Basin, SW Bulgaria. Seams Ia, I, IIa+b, III, IV and V from the coal-bearing Bobov Dol Fm. were sampled to provide insights into the peat forming vegetation and depositional environment based on detailed organic petrological and geochemical study.The petrographic composition indicates that both coals and carbonaceous shales contain predominantly terrestrial organic matter with abundant huminite macerals and locally enriched liptinite macerals. Inertinite is rare or absent. Good tissue preservation in seams I, IV and V indicates deposition under wet sedimentary environment, whereas predominance of detrohuminite and lower Tissue Preservation Index (TPI) in seams Ia, IIa+b and III are linked to enhanced humification of the plant remains due to changes in the hydrological regime. The low percent of inertinite and the overall high Gelification Index (GI), however, argue for peat formation under wetter climatic settings, whereas low to moderate ash yields of coal samples indicate organic matter deposition in oligo- to mesotrophic topogenous mires. Reconstructed evolution of the environmental settings during peat formation denotes differences which might be caused by changes in the hydrological regime and tectonic activity.The biomarker composition shows prevalence of gymnosperm-derived sesqui- and diterpenoids, followed by lower concentration of n-alkanes (apart from the carbonaceous shale samples from seam Ia), whereas angiosperm-derived non-hopanoid triterpenoids, acyclic isoprenoids, steroids and hopanoids, are generally present in minor amounts. Diterpenoid composition indicates dominant contribution from Cupressaceae and Pinaceae conifers. Minor amounts of predominantly lupane-type non-hopanoid triterpenoids denote limited development of angiosperm vegetation, presumably mostly related to Betulaceae family. Relative abundance of mid-chain (n-C21–25) n-alkanes, associated with elevated proxy ratio (Paq) furthermore, suggest possible contribution from aquatic macrophytes to peat formation. Very low hopane concentrations and low/moderate ββ/(ββ + αβ) hopane ratios imply minor aerobic bacterial activity under mild acidic conditions. The presence of inorganic carbon suggests that environmental acidity might be controlled by the occasional input of neutral to slightly alkaline ground waters. Moderate sulfur contents and the occurrence of hopenes denote anaerobic bacterial activity after organic matter burial.Low maturity of the organic matter and limited hydrocarbon generation potential is indicated by the low huminite reflectance, hopane (C31 22S/(22S + 22R)) and sterane (αααC29 20S/(20S + 20R)) isomerization ratios, as well as Rock-Eval parameters, Tmax and Production Index (PI).

Coal facies of the Middle Permian Baruunnaran deposit, South Mongolia

The Baruunnaran coal deposit is located in the northeastern part of the South Gobi Basin, southern Mongolia, and hosted in the middle Permian Tavantolgoi Formation. In this paper we present indices of coal facies determined from 34 coal samples obtained from three seams in the lower and upper part of the formation (III, IXG and X), by studying their organic petrography and the geochemistry of the coal ash. The results of coal petrography revealed that seams III, IXG and X are composed of 46.9-80.9 vol.% vitrinite, 11.6-47.5 vol.% inertinite and 1.2-18.2 vol.% liptinite. In samples from seams III and X the average content of mineral matter is low at 11 and 13.4 vol.%, respectively, and 6.3 vol.% in seam IXG, and consists of clay, silica, pyrite, carbonate, and other minerals. The inorganic content mostly occurs as fillings of cell cavities, cracks, and fissures of vitrinite and inertinite macerals. The vitrinite random reflectance values range from 0.81-1.07%. The Gelification Index and Tissue Preservation Index suggest the peats accumulated in wet forest swamp environments with high tree density. The majority of the seams accumulated in mildly oxic to anoxic conditions with good tissue preservation. The peat mire water ranged from weakly to strongly acidic. Further, it was determined by Al2O3/TiO2 ratios that the clastic sediments were probably sourced from volcanic basement characterized by intermediate felsic composition.

Maceral composition, coal quality and depositional environments of the middle Permian Ukhaakhudag coal deposit, South Mongolia

The Ukhaakhudag coal deposit is located c. 560 km SSE of the city of Ulaanbaatar in the northeastern sector the South Gobi Basin. The coal-bearing strata is part of the middle Permian Tavantolgoi Formation. This study aims to determine the coal petrographic composition and depositional environments of five coal seams in the lower part of the deposit based on petrographic and chemical analyses of 106 composite samples. Vitrinite ranges from 12 to 64 vol.%, and inertinite varies between 9 and 68 vol.%. Liptinite ranges from 1 to 7 vol.%. Microlithotype analyses indicate that coals are primarily vitrinertite, few coals are classified as trimaceralic microlithotypes duroclarite and clarodurite. The inorganic fraction in the studied coals is mainly composed of clay, small amounts of silica, carbonate, and pyrite minerals. The vitrinite random reflectance values of the samples vary between 0.93-1.16 %. Volatile matter content varies from 26.10 to 41.48 wt.% (dry ash free basis). Ash, moisture, and sulfur contents vary between 11.20-44.76 wt.%, 1.63-6.03 wt.% and 0.49-1.67 wt.%, (air dried basis) respectively. Based on random vitrinite reflectance values and volatile matter content, the studied coals are classified as coking (Ch4), fat (Ch5), 1/3 coking (Ch6), gas fat (Ch7) based on the Mongolian system and medium to high volatile bituminous coal when using the ASTM system. The Gelification Index and Tissue Preservation Index of the studied samples suggest most seams accumulated in wet forest swamps with a high tree density. The Middle Permian peats from this location accumulated in mostly alternate oxic and anoxic mire conditions. The climate was drier during the peat accumulation of Seam 0, but it became warmer, and humidity increased starting from Seam 3 accumulation.

Paleoenvironmental Settings of the Soma Coal Basin (Turkey): Insights from Maceral Data, Biomarker, and Carbon Isotopic Composition.

Organic geochemical (TOC, pyrolysis, biomarker) and petrographic (maceral analysis) investigations together with organic carbon isotope studies were carried out to characterize in detail the depositional environment, determine the organic matter type, and assess the hydrocarbon production potential of three coal seams (KP1-upper, KM3-middle, and KM2-lower) in the Soma (Manisa, Western Anatolia) coal field in Turkey. The total organic carbon value of the upper coal seam ranged between 11.7 and 55.75%, the middle coal seam between 20.12 and 62.86%, and the lower coal seam between 50.03 and 65.71%. Coals in all three seams are characterized by low hydrogen index (HI) values (<151 mg HC/g TOC), low bitumen index (BI) (<19 g HC/g TOC), and quality index (QI) between 23 and 156 mg HC/g TOC. According to Rock-Eval pyrolysis data, the organic matter type of the coals is type III kerogen. Huminite reflectance, Tmax, and biomarker data (22S/22S+22R (C32) sterane, ββ/(αα + ββ) (C29) sterane, and MPI-1) indicate that the organic matter is not thermally mature and that the Soma-Manisa coal has reached the sub-bituminous rank. Rock-Eval data shows that coal is gas-prone and has not reached the maturity threshold required for initial gas production. The dominant maceral group is huminite while liptinite and inertinite macerals have been found in minor amounts. Groundwater index (GWI), vegetation index (VI), tissue preservation index (TPI), and gelification index (GI) parameters indicate a transition from limnic-limno-telmatic to limno-telmatic-telmatic environment from the upper seam to the lower seam. N-Alkane distributions show that paleoclimatic conditions have changed from KP1 to KM2. The higher abundance of pristane compared to phytane and low C35/C31-C35 homohopane index values demonstrate that the coals were deposited in a suboxic-oxic environment. The predominance of n-alkanes with generally high carbon number, relative variable abundances of C27-C28-C29 steranes, δ13C values, C/N ratios, and very low gammacerane index indicate a terrestrial ecosystem with nonmarine influence, although algae and microorganisms also contributed to the biomass.

Petrographic and geochemical analysis of Barmer Basin Paleogene lignite deposits: Insights into depositional environment and paleo-climate

The current study attempts to characterize the samples from Kapurdi, Giral and Sonari lignite mines of Barmer Basin within Rajasthan Tertiary Lignite deposits using petrographic and geochemical techniques. The data generated has been studied in order to better understand the geochemical properties, hydrocarbon potential, depositional environment and paleo-climatic condition of the paleo-mires of these lignites. The proximate analysis of the samples reveals that the average ash content of the Barmer Basin is 11.93 %, the average moisture content is 14.08 %, average volatile matter yield is 42.03 % and the average fixed carbon is 31.95 %, which suggesting that the physical properties of lignite are dominated by volatile matter on dry basis. The ultimate investigation reveals the chemical properties of the lignite with the average carbon content found to be 58.79 wt%, hydrogen value 3.83 wt%, nitrogen percentage 1.60 wt% and sulphur content 2.75 wt%. This clearly indicates high sulphur concentration in Barmer lignite deposits, based on dry basis. The lignite samples subjected to FTIR studies identified aliphatic CH group, aromatic CO group, hydroxyl OH and Aldehyde HCO group. The Rock-Eval pyrolysis studies have been carried out to know the coalification profile of the deposits and hydrocarbon source rock potential. The varying behaviour between brown coal lithotype are primarily reflected by changes in oxygen index values, whereas hydrogen index values demonstrate a more pronounced correlation with coal type rather than the level of maturation. The results show the average total organic carbon (TOC) 47.29 %, S1 peak 2.18 mg HC/g, S2 peak 88.70 mg HC/g, S3 peak 19.22 % mg CO2/g, Tmax 410.53 °C, hydrogen index 219.2 mg HC/g TOC and oxygen index 46.33 mg CO2/g TOC. According to petrographic investigations, the huminite macerals dominate followed by liptinite and inertinite maceral groups in mineral matter-free basis. In all the three different lignite mines, the huminite group dominates with preserved sub-maceral ulminite indicating less transformation of structured plant matter. Reconstruction of depositional environment and paleo-climatic condition of the paleo-mires has been attempted by using organic petrographic indices. The high gelification index (GI) and low tissue preservation index (TPI) values suggest a prolonged wet environment during the decomposition of organic material, accompanied by a gradual subsidence process. The ground water influence index (GWI) and vegetation index (VI) denote ombrotrophic to mesotrophic hydrological conditions of basin at the time of deposition.

Variation of molecular structures affecting tar yield: A comprehensive analysis on coal ranks and depositional environments

Coal with a tar yield ≥ 7 %, which is measured in the Gray-King assay, is called tar-rich coal in China. However, the comprehensive impact of coal ranks and depositional environments on tar yield is still unclear. Here, the coal petrology, molecular structure, and depositional environment of the samples were thoroughly investigated to clarify the influence of the coal rank and depositional environment on the tar-rich coal. The difference in the tar yield is attributed to the molecular structure. Concerning Fourier transform infrared (FTIR) spectroscopy, the high tar production resulted from the existence of relatively long aliphatic side chains and high aliphatic hydrogen content. For the 13C nuclear magnetic resonance analysis, the structure of the aliphatic carbon also played a crucial role in tar formation. Among these, the various unstable structural parameters (falH/fas, (fas + fap)/fa', fas/fa', falH/fal*) and weak bonds could improve the tar yield. Furthermore, the molecular structures were also controlled by the coal rank. More specifically, the CH2/CH3 in FTIR and the falH, falH/fa*, fas/fa’ in 13C NMR had similar patterns with coal rank, which was close to the pattern between the coal rank and the tar yield. This effect also indicated that the tar yield was mainly influenced by bridge bonds, aliphatic side chains, and branched aromatic carbon. Between similar coal ranks, the molecular structure differences originated from the depositional environment. For the coal facies, the tissue preservation index (TPI) and vegetation index (VI) were negatively correlated with CH2/CH3, Hal/H, and “A factor”. In contrast, they were positively correlated with the oxidation degree (Io2). The gelification index (GI) was also positively correlated with CH2/CH3 and Hal/H. Consequently, the coal-forming environment with a relatively high degree of decomposition, low woody tissue content, and high gelification can form key molecular structures easier, which is beneficial for the tar yield.

COAL FACES STUDY BASED ON MACERAL CHARACTERISTICS IN KLASUAT AREA, KLAYII DISTRICT, SORONG REGENCY, WEST PAPUA

This study aims to determine the characteristics of the coal maceral and the Klasuat coal facies which are included in the Klasaman Formation, Salawati Basin, West Papua of Upper Miocene - Pleistocene age. The characteristics of coal maceral can be identified using maceral analysis, vitrinite reflectance value analysis, interpretation of the depositional environment based on Diessel, and Lamberson and Calder diagrams. The methodology applied in this research attempts to expand the research of coal at the local scale in the Salawati Basin, and to determine variations in coal characteristics controlled by differences in the lateral depositional environment. Based on the results of facies reconstruction of the depositional environment using four parameters TPI (Tissue Preservation Index), GI (Gelification Index), GWI (Ground Water Index) and VI (Vegetation Index) and plotted in the Diessel and Calder diagrams, it is found that the Klasuat Coal Layer was deposited in the facies limnic depositional environment.

Miocene organic-rich layers of the Saouef Formation (Oriental Tunisia); insights into temporal and spatial variability of environmental conditions during deposition

Miocene organic-rich sediments (coal and carbonaceous clays) from the La Falaise section of the Saouef Formation have been investigated by organic petrographic, palynofacies and organic geochemical approaches. The results are compared with data obtained during a previous study of the nearby Saouef section. The sedimentary succession is built up by repetitive sedimentary sequences (i.e., parasequences) deposited during progradation and retrogradation, respectively. The coal, or carbonaceous layers, developed during the establishment of clay-dominated sedimentation.The organic-rich layers within the samples, containing high amounts of mineral matter, are dark brown, with a stratified texture and are classified as humic coal. Microscopically, the huminite group dominates the maceral composition of the carbonaceous clays and lignite (av. 75% mmf). The variable degrees of the tissue preservation index (TPI) and highly fluctuating vegetation index (VI) values provide evidence for different contributions of vascular plants vs. herbaceous vegetation and macrophytes, to peat formation. Higher contributions of macrophytes (e.g., reed grasses) to peat accumulation at La Falaise are concluded, based on n-alkane distributions. High mineral matter contents and changing gelification index (GI), and ground water index (GWI) values, found in both sections, provide evidence for rheotrophic hydrogeological conditions, and peat formation within wet forest swamp to inundated marsh environment. The low sulphur contents attest to peat formation within a freshwater environment and the relative proportions of ββ to (ββ + αβ)-C31 hopanes argue for slightly acidic conditions. In comparison to the results of the Saouef section (average pH of 5.6), a lower pH (4.2) is revealed from the average hopane isomerization ratio of the La Falaise samples.The palynofacies investigation of the La Falaise deposits indicates the dominance of phytoclasts over amorphous organic matter (AOM) in most of the samples and suggests good preservation of the higher plant remains. In contrast, increased degradation of plant tissues under oxygen-deficient conditions is concluded from the enhanced proportions of AOM found in several of the previously investigated Saouef samples. The molecular analysis of hydrocarbons from all the samples indicated the dominance of n-alkanes and hopanoids. The obtained pristane/phytane ratios argue for sub-oxic conditions during peatification at La Falaise, whereas data from our previous study of the Saouef section provided evidence for a reducing environment. Terpenoid hydrocarbon compositions reveal highly variable contributions of conifers and angiosperms to peat formation, consistent with previous findings at the Saouef sampling site. The presence of polycyclic aromatic hydrocarbons (PAHs), as well as fusinite, provides evidence for mire or forest fires.The comparison of the results from lignite of both sections of the Saouef Formation indicate comparable, highly variable conditions during peat accumulation, probably governed by eustatic sea level changes. The peatlands most likely developed due to the establishment of flood basins situated between alluvial ridges. The obtained regional differences are suggested to reflect slightly different hydrological conditions and associated vegetation cover in the peatlands.

Effect of the depositional environment on the formation of tar-rich coal: A case study in the northeastern Ordos Basin, China

Tar yield, as a basic evaluation index of tar-rich coal, is unclear to be affected by the depositional environment. In this work, the vertical variations in tar yield, macerals, and major/trace elements were investigated for highly volatile bituminous coal in the Ordos Basin, China, to analyse the effect of the depositional environment on the tar-rich coal distribution. The results show that the tar yield more than 7% (tar-rich coal) accounts for 70% in this formation, which formed in a depositional environment with a stable supply of terrestrial sediments, a warm and humid climate, and weakly reducing to reducing conditions. For the coal facies, all samples were distributed into two groups of coal facies, with the first group containing limnic, dry forest swamp, wet forest swamp and another group contains bog, forest bog. Moreover, limnic and bog with less woody tissue and a higher water table contribute to the higher tar yield of coal. Correspondingly, the vitrinite content and the gelation index (GI) were positively correlated with tar yield, and the tissue preservation index (TPI) and vegetation index (VI) were negatively correlated with tar yield. The inorganic composition, the ash yield, which is mainly composed of SiO2 and Al2O3, reduced the tar yield. CaO and MgO in small proportions promote the tar yield of coal due to catalytic effects. The relationship between tar yield and the parameters Sr/Ba, Sr/Cu, Cu/Zn, (Cu + Mo)/Zn, U/Th, Ni/Co, δU, Ce/La, δCe, and δEu are also discussed here. It was concluded that the paleoclimate had little effect on the tar yield, while the paleoreduction conditions had an obvious influence on the tar yield. The depositional environment with higher reduction and lower salinity conditions was conducive to the increase in tar yield of coal. This work aims to accurately identify and predict tar-rich coal based on its depositional environment, which provides guidance for its exploration and development.

Petrographic composition of coal within the Benue Trough, Nigeria and a consideration of the paleodepositional setting

The petrographic composition of Cretaceous-age coals hosted in the Benue Trough, Nigeria is presented and discussed in terms of the paleodepositional settings that influenced the coal-bearing formations. The Benue Trough is a failed arm of the triple junction of an inland sedimentary basin that extends in a NE-SW direction from the Gulf of Guinea in the south, to the Chad Basin in the north. A total of twenty-nine (29) coal samples were obtained from nineteen coal localities in the Upper (UBT), Middle (MBT), and Lower Benue Trough (LBT). The high average volatile matter yield, low average ash yield, high calorific value (24.82 MJ/kg, on average), and low sulphur values indicate good quality coal deposits. The organic matter is dominated by vitrinite, reported at an average of 59.3% by volume (mineral-matter free). Variation was noted in the inertinite content across three sub-regions. Liptinite macerals were not commonly observed in the studied samples and were absent in the MBT samples. Coal facies studies decipher the paleoenvironmental conditions under which the vegetation accumulated. Indices commonly used are the gelification index (GI), tissue preservation index (TPI), ground water index (GWI and variations), vegetation index (VI), and wood index (WI). Comparing the array of coal facies models applied, the MBT samples differ from the UBT and LBT samples, concurring with the coal quality data. The UBT and LBT coals formed in an upper deltaic to drier piedmont plane depositional environment, while the MBT coal formed in a lower deltaic marsh to wet forest swamp depositional environment. All samples indicate an ombrotrophic paleomire. In view of the modified equations and the plots used, interpreting depositional environments from just a single model is not reliable.

Geochemical, mineralogical, and petrological characteristics of the Cretaceous coal from the middle Benue Trough Basin, Nigeria: Implication for coal depositional environments

The Benue Trough Basin (BTB) of Nigeria is geologically and geo-morphologically subdivided into upper, middle, and lower segments. The BTB is the subject of geological research due to its rich coal deposits that have the potential for oil and gas. The purpose of the present study is to examine the origins, depositional environments, and thermal history of the selected coals and the processes that influence their quality. Coal samples from different open cast coal mines in the middle BTB were examined using proximate and ultimate, x-ray diffraction (XRD), x-ray fluorescence (XRF), laser ablation induced coupled plasma (LA-ICPMS), and petrographical analyses. The coal samples contained mainly quartz, kaolinite, and organic carbon. The XRD spectra peaks revealed the triclinic and monoclinic structure of kaolin. The SiO2/Al2O3 ratios confirmed the dominance of quartz and kaolinite. The Ni/Co versus V/Cr, Cu/Zn, and V/Mo values in the studied coals suggest oxic depositional environments, whereas the V/(Ni + V) and V/(V + Cr) values indicate oxic to suboxic conditions. The Ce/Ce∗ values are slightly below 1, which indicates a suboxic depositional environment. Maceral texture is indicative of transformations from sub-bituminous to high volatile C or B bituminous coal. The maceral components and mineral matter (≥10%) of the studied coals imply deposition in the planar margin mire, and a river system of planar margin mire environments, respectively. The high gelification index (GI) and tissue preservation index (TPI) values indicate peat accumulation developed within a wet forest swamp. The ternary diagram of the maceral component suggests deposition in a wet moor environment with intermittent moderate to high flooding episodes. The studied coals are sub-hydrous vitrinite inferring hydrogen-poor and thermally immature characteristics. The low V and Ni contents, low H/C and high O/C, indicate Type Ⅲ terrestrial organic matter with the potential to generate gaseous hydrocarbons. The investigated coals were deposited by the river within telmatic, limnic, and limno-telmatic zones in the planar margin mire depositional environments. Overall, the integrated petrologic and geochemical data used in this study provides a reliable approach for the assessment of coal depositional environments.

Elemental geochemistry and organic facies of selected cretaceous coals from the Benue Trough basin in Nigeria: Implication for paleodepositional environments

Benue Trough basin is geologically subdivided into three segments. It consists of marine and continental sediments that are affected by folding movements. In the upper section, the continental coal-bearing Campano-Maastrichtian-age is found within Gombe Sandstone and the Cenozoic Kerri-Kerri Formation of the Tertiary. In the middle segment, the late Turonian/early Santonian coal-bearing Awgu Formation lies conformably on the Ezeaku Formation. In the lower part, shales at Nkporo mark marine incursion and deposition of the Maastrichtian Mamu Formation coal measures. Cretaceous coal samples taken from the three segments of Benue Trough basin were examined using ultimate and proximate, organic petrographic, x-ray fluorescence (XRF) and laser ablation-induced coupled plasma spectroscopy (LA-ICPMS) analytical techniques. Results of trace element ratios, Ce/Ce* values (“where Ce* is the theoretical Ce value derived from a chondrite-normalized rare earth element (REE) pattern”), authigenic uranium values, and low hydrogen content indicate deposition under oxic to suboxic conditions. However, the V/Ni and V/Sc ratios indicate under oxic, suboxic to reducing conditions. The Y/Ho values for selected coals are lower than the range for seawater, indicating terrigenous influence. The Sr/Ba values indicate low influence of saline water during deposition and a strong continental rather than marine influence. High value of vitrinite and low proportion of liptinite/intertinite suggest that peat in the study areas were situated on the irregular basin floor where sediment thicknesses vary from place to place thus the depositional environments shifted causing mineral matter filling in coal. Based on the tissue preservation index (TPI) and gelification index (GI), LFB, CHK, OKB, LMZ, IMG; and ENG (high GI and high TPI) were deposited in telmatic facies; wet-forest swamps with rapid organic matter accumulation. This trend indicates mild humification and strong gelification of plant tissues which ascribed to high rate of subsidence with wood- and bark-derived telovitrinite. The MGA peats were deposited in terrestrial facies in a dry-forest swamp with wood-derived telo-inertinite. The coal samples code-named IMG and ENG were deposited in planar margin mires. However, coal samples code-named LFB, CHK and LMZ were deposited in planar central mires. Lastly, OKB and MGA were deposited in transitional-wet and transitional-dry mire. The low V and Ni concentrations, low H/C, high O/C, high C/N, and very low N/C ratios <0.05 implies Type III land-plant organic matter that is not oil-prone. The depositional environments interpretations of investigated coal seams indicate that the coals were deposited within a telmatic, limnic, limno-telmatic and open march zone. Generally, a combination of results from inorganic geochemistry and organic petrology is required for precise and all-inclusive determination of coal depositional environments.

Construct a Paleo-Limnological Environment Based on Coal Petrography; Case Study, Two Selected Coal Seams, North Crowsnest Open-Pit Mine, Canada

The Crowsnest coalfield is a separated structural coalfield at the East Kootenay basin within southeast British Columbia. Selected Jurassic-Cretaceous two coals seam S-10 and S-C of the Mist-Mountain formation were investigated from the points of coal petrography to construct a Paleo-limnological setting. Twenty-two channel coal samples were assembled and measured from S-10 and S-C coal seams. Vitrinite reflectance measuring of the S-10 coal concern to low-volatile bituminous (1.61, on average). While the vitrinite reflectance measurements of S-C coal seam show an average value of 0.98 related to high-volatile bituminous. Petrographic analysis demonstrates that the S-10 coal seam appears to be rich in inertinite than the S-C coal seam that appears rich in vitrinite. Applying coal facies indices of Tissue Preservation Index, Gelification Index, Ground Water Index Vegetation Index and coal facies diagrams for the studied coal seams aid to suggest a condition of the depositional Paleo-environments. The results promote Paleo-depositional sites of telmatic to limno-telmatic setting of rheotropic systems swamp. The obtained results show a trend of increase in both herbaceous flora and anoxic waterlogged limo-telmatic setting toward the younger coal seam S-C than the older S-10 coal seam.

Selective mine plan based on coal quality distribution of Batu Ayau formation, Murung Raya-Central Kalimantan

Coal quality, which eventually controlling coal’s behavior during preservation, combustion, and other forms of utilization, are defined by the depositional environment in which the peat was formed. Batu Ayau Formation is a well-known coal-bearing formation of Barito Basin and has been thoroughly explored. The aim of this study, which differs from previous studies, is to figure out the correlation of depositional environment to the coal quality of Batu Ayau Formation and anticipate the less desired coal quality from being mined. The depositional environment is determined through the stratigraphic section compared to Horne model, supported by coal facies determination using Tissue Preservation Index (TPI) vs Gelification Index diagram. Ash and sulphur content (weight %) data from 4 seams are integrated to the lithostratigraphic column. The coal quality distribution is defined from good correlation. The coal-bearing depositional environment of the studied area is transitional – upper delta plain. The ash content is ranging in 5.20-8.64wt% and total sulphur is ranging in 0.34-1.28%. The position of depositional environment that is closer to open marine, which is dipping westward, is preferable in terms of quality. Hence, coal on the center part of the research has preferable coal quality to be mined.

Evaluation of hydrocarbon potential with insight into climate and environment present during deposition of the Sonari lignite, Barmer Basin Rajasthan

Lignite samples from the Sonari mines of Barmer Basin, Rajasthan, India have been studied for the first time by applying advanced petrochemical techniques. The objective of the study was to reconstruct Paleomire conditions and to examine the source rock potential of the lignite-bearing sequence. Based on the mean huminite/vitrinite reflectance values (0.24–0.31%Ro), all of the samples studied are lignite B in rank. Geochemical analysis results show, the atomic ration H/C and O/C ranges from 0.03–0.15 and 0.27–0.61 respectively, hydrogen index (HI) and oxygen index (OI) ranges from 173 to 256 mg HC/g TOC and 29–55 mg CO2/g TOC respectively, with Tmax value (415–416 °C), entails these lignites are thermally immature and contain type III kerogen. The studied lignites have total organic carbon (TOC), and S2 values vary from 41.24–49.19wt% and 78.53–119.81 mg HC/g rock, respectively, which indicate that these lignites may be served as good hydrocarbon source rock.The lignites are principally composed of huminite (mean 47.5 vol%) and inertinite (mean 31.4 vol%) group of macerals with a low concentration (mean 8.5 vol%) of liptinite macerals. The predominance of attrinite in the Sonari lignite samples suggests that woody vegetation has undergone significant degradation. Petrographic indices such as TPI (Tissue preservation index; 0.92–2.13), GI (Gelification index; 0.97–8.25), GWI (Groundwater influence index; 0.34–1.50), and VI (Vegetation index; 0.16–1.84) indicate deposition in a wet forest paleomire and peat formation under ombrotrophic to mesotrophic hydrogeological conditions. Ternary plots based on maceral and microlithotype entails fluctuating water table condition during peat deposition.The GC-MS (Gas chromatography–mass spectrometry) data shows that the ratios, Pr/Ph pristine/phytane (˂1), Pr/C17 (0.57), Ph/C18 (0.25) and carbon preference index (CPI) value 3.73 along with δ13C (−25.04%) values indicate that the Sonari lignites are composed primarily of gymnosperms taxa which formed under relatively dry and cold paleoclimatic conditions. Besides, FT-IR (Fourier-transform infrared spectroscopy) spectra give the signature of a C–H aliphatic stretching region and predominate methylene group in the aliphatic carbon region, which is also observed in the NMR (Nuclear magnetic resonance).

Deposition characteristics of pliocene coals in the denizli region (SW Turkey) via organic petrography, geochemistry, and stable isotope composition

The objective of this study is to identify and evaluate the organic geochemical properties, paleo vegetation, and paleo depositional environment of coals in Denizli (SW Turkey). Organic geochemical and petrographic investigations, scanning electron microscopy, X-ray diffractometry, and palynological and stable isotope (δ2H, δ13C, δ15N, δ18O and δ34S) investigations have been performed. Coal, clayey coal, and coaly claystone samples from the study area have gas and oil production potential according to their total organic carbon (0.59–48.30 wt%), hydrogen index (56–286 mg HC/g TOC), oxygen index (30–121 mg CO2/g TOC) and S2/S3 (0.47–9.59) values. Dominant maceral assemblages included huminites and low amounts of liptinite group macerals. Tissue preservation index (0.39–5.13), gelification index (4.11–96.83), groundwater index (0.40–8.77) and vegetation index (0.49–42.67) parameters indicate a limno-telmatic environment and increased woody tissue. Mean random huminite/vitrinite reflectance values (ranging from 0.23 to 0.41 %Ro) denote lignite and sub-bituminous C and B ranked coals. Carpinus, Alnus, Zelkova, Platanus-Salix, Carya, and Ostrya were found through palynologic investigations. In addition, freshwater algae Botryococcus was detected in coal samples from Denizli. δ13C, δ15N values and C/N ratios indicated a terrestrial C3 ecosystem. Some sterane and tricyclic terpane ratios and aromatic biomarkers have shown that high plant input, immature organic matter and oxic-suboxic conditions are predominant in the depositional environment.

Coal Petrology Effect on Nanopore Structure of Lignite: Case Study of No. 5 Coal Seam, Shengli Coalfield, Erlian Basin, China

The pore structure of lignite reservoirs is affected mainly by the maceral composition of coal and depositional conditions due to geothermal effects without thermogenic hydrocarbon generation. Low-temperature nitrogen adsorption (LT-NA) and low-temperature carbon dioxide adsorption (LT-CA) were used to characterize nanopore structure. Sub-maceral identification allowed characterization of coal petrology features. The coal samples were rich in huminite—mainly attrinite and densinite—and had medium inertinite content, dominated by fusinite. The micropore volume varied from 0.036 to 0.077 cm3/g, controlling the pore specific surface area. Three pore types were identified from LT-NA isotherms. Hysteresis coefficients were used to describe quantitatively the pore types. Low tissue preservation index and vegetation index, moderate gelification index, and groundwater influence values indicate that the No. 5 coal seam (Shengli coalfield, Erlian basin, China) was deposited in limnic to limno-telmatic environments with relatively high levels of reduction and supply of marginal aquatic/herbaceous vegetation. Poor preservation of plant structure and hydrodynamic conditions, more developed marginal aquatic/herbaceous vegetation, and high ratio of huminite to inertinite contributed to high micropore content and low mesopore content. Based on sharp variations in coal macerals, coal facies indices, dried ash yield (Ad), and organic sulfur (So,d), three sedimentary cycles were distinguished. Pore structures were controlled by the sedimentary environment. Micropores increased with enhanced reduction and reduced oxidation. When the redox of the sedimentary environment showed little variation, mesopores increased with rising hydrodynamic conditions.

Pore Structure Characteristics of Coal and Their Geological Controlling Factors in Eastern Yunnan and Western Guizhou, China.

Coalbed is the carrier for coalbed methane (CBM) enrichment and migration. The pore structure characteristics of coal and their main geological controlling factors are critical to the exploration and development of CBM. In this paper, 20 coal samples were collected from eastern Yunnan and western Guizhou, China. Based on vitrinite reflectance, proximate analysis, maceral analysis, and low-temperature N2 adsorption/desorption (LT-N2GA) experiments, the hysteresis coefficient of low-temperature N2 desorption was proposed, the types of pore structure were identified, and the effects of coal facies and rank on the pore structure were revealed. The results show that the Ro,max values of the 20 coal samples are between 0.74 and 3.38%, which belong to medium- and high-rank coal. In the coal macerals, the vitrinite is mainly collodetrinite. The inertinite is dominated by semifusinite, and some coal samples contain exinite. The coal samples investigated can be divided into two types. Type A samples mainly contain open pores, while type B samples are rich in bottle-shaped pores. Compared with type A coal samples, type B samples have the characteristics of smaller total pore volume (TPV), smaller average pore diameter (APD), larger specific surface area (SSA), and larger hysteresis coefficient. The coal samples are located in three regions of different coal facies, including low-level swamp (reed) facies, wetland herbaceous swamp facies, and wet forest swamp facies. The tissue preservation index (TPI) values of most coal samples are less than unity, which indicates that herbaceous plants have absolute dominance in the coal-forming plants in eastern Yunnan and western Guizhou. The maximum vitrinite reflectance (Ro,max), gelification index (GI), TPI, vitrinite content (V), inertinite content (I), Barrett-Joyner-Halenda pore volume (VBJH), Brunauer–Emmett–Teller SSA (SBET), and low-temperature N2 desorption total hysteresis coefficient (Ht) were clustered using the R-type cluster analysis method. It is found that TPI is the main controlling factor of the pore structure of type A coal samples, while the pore structure of type B coal samples are jointly controlled by TPI and coal rank. Type B coal samples are mainly located in Zhuzang and Laochang high-rank coal research areas, while the distribution of type A coal samples is mainly in other medium–high-rank coal research areas. These results will contribute to the exploration and development of CBM and also guide the study of pore structures of other unconventional gas reservoirs.