Geochemical variations of major,trace, rare earth elements in some Gondwana and Eocene coals of India with a comparison of their germanium,lithium, and mercury content

The geochemistry of major, trace, rare earth elements (REEs), with special reference to Ge, Li, and Hg in selected Gondwana and Eocene coals, has been studied. Major oxide and trace element ratios have been utilised to compare the tectonic setting, provenance of source rocks, and paleoweathering conditions that prevailed the during formation of these coals. The Gondwana coals have a higher mean mercury and ash content (244.5 μg/kg and 17.2 %, respectively) than the Eocene coals (142.1 μg/kg, 8.9 % respectively). The major oxides, SiO₂, Fe₂O_3, and Al₂O_3, in Gondwana and Eocene coals, are enriched relative to the upper continental crust (UCC), Chinese and American coals. The UCC normalized trace element concentration coefficients of the Gondwana and Eocene coals show enrichment in Ge, Se, Th, Co, Mo, Sn, W, and Li. The mean Ge and Li concentrations (mg/kg) in Gondwana (106.7, 154.7) and Eocene (120.0, 252.6) exceed the corresponding values in world coal (2.2, and 12). The Rajmahal coals have the highest mean Ge concentration (168.8 mg/kg) among the Gondwana coals while Eocene coals from East Jaintia Hills have the highest mean value (343.7 mg/kg). The Gondwana coals have a higher mean As concentration (3.5 mg/kg) in comparison to the Eocene coals (1.9 mg/kg). The mean of the rare earth elements in Gondwana (24.1 mg/kg) is higher than that in Eocene coals (11.3 mg/kg) and these values are less than the World coals (68.5 mg/kg). Both the Gondwana and Eocene coals are enriched in light rare earth elements (LREEs). However, among the Eocene coals, the Meghalayan coals show REE enrichment in comparison to Assam coals. Both the Gondwana and Eocene coals were formed in warm and humid climates under oxic conditions with moderate weathering of the source rocks.     

Trace elements and their variation along seam profiles of certain coal seams of Middle and Upper Barakar formations (Lower Permian) in East Bokaro coalfield,district Hazaribagh,Bihar, India

Trace-element data are presented for the first time for any coal seam in India, across a full working section, based on systematically collected channel samples of coal, together with their maceral composition. The trace-element variation curves along the seam profile are presented together with group maceral compositions of Kargali Bottom, Kargali Top, Kargali, Kathara, Uchitdih, Jarangdih Bottom, Jarangdih, and Jarangdih Top seams, East Bokaro coalfield. The Kathara and Uchitdih seams have also been sampled at two other localities and lateral variation in data in their trace-element and maceral compositions is also evaluated.The East Bokaro coals have: Ba and Sr > 1000 ppm; Mn < 450 ppm; Zr < 400 ppm; Ni and V < 250 ppm; Cr < 185 ppm; La < 165 ppm; Cu, Nb, and B < 125 ppm; Pb, Co and Y < 75 ppm; Ga, Sn, Mo, In and Yb < 15 ppm; Ag 2 ppm; and Ge 7 ppm. Petrographically, the coals are dominant in vitrinite (33–97%), rare in exinite (<15%), and semifusinite (0.8–49%) is the dominant inertinite maceral, with variable mineral and shaly matter (11–30%), graphic representation of trace elements versus vitrinite, inertinite, and coal ash indicates the affinity of (a) vitrinite with Cu, Ni, Co, V, Ga and B; (b) inertinite with Nb and B; and (c) coal ash (mineral matter) with Pb, Cu, Ni, La, Mn and Y; Ba, Cr, Sr, Zr, Cu and Ni are of organic as well as inorganic origins.The trend of the variation patterns and average compositions of the different seams are shown to be distinct and different. The variation along the same profile is inferred to be different for different seams of the coalfield.Trace-element data for certain coals of seams from different coalfields in the Gondwana basins of India are presented. There is a wide difference for each of these basins with respect to certain elements. This is suggestive of the proportions of Cu, Ni, V, Y, Ba, Sr, Cr, B, Zr and Ag, characterizing the different Gondwana Basins.     

A statistical approach to the study of the distribution of trace elements and their organic/ inorganic affinity in lower Gondwana coals of India

Trace-element analyses of seventy six coal samples representing all the major Lower Gondwana coal basins of India were carried out. Eighteen trace elements, viz., B, Ba, Co, Cr, Cu, Ga, Ge, La, Mn, Mo, Nb, Ni, Pb, Sn, Sr, V, Y and Zr were determined quantitatively in coal ash. An attempt was made to correlate the coals of different coalfields on the basis of multivariate analysis. In addition, the organic/inorganic affinities between the trace elements were established by the coefficients of correlation between the trace elements and ash present. A synthesis of the data reveals that there is similarity in the concentration ranges of trace elements among the coal seams of different coalfields, but the possibility of environmental differences exists due to the statistically different multivariate means of the trace-element concentrations.It is inferred that Ge, Cr, Y and La occur in these coals as organo-metallic complexes and chelates. The elements Ni, Co, Ga, V and Cu show both organic and inorganic association, whereas Mn and Ba are exclusively incorporated in the inorganic fractions.     

Petrographic,chemical and trace-elemental composition of the coal of Sohagpur coalfield,Madhya Pradesh,India

The Sohagpur coalfield is a remnant of the Son valley basin of Gondwana deposition and can be subdivided into three major subbasins from west to east: Rungta-Amlai, Kotma and Bijuri. Thick coal seams occur in the Barakar Formation (Lower Permian) and are being worked extensively.Petrographic, reflectance, chemical and trace-elemental studies on samples of coal representative of the coal seams of the different subbasins have been carried out, and the results are presented here. Petrographically, the coals of one subbasin are different from those of another subbasin and are mainly composed of vitrinertite I, and vitrinertite V, that alternates with fusite. Vitrite increases in proportion in the coal seams towards the eastern part of the coalfield, and sclerotinite occurs in increased proportion in coal seams towards the western part. The reflectance in oil (Ro_max) varies from 0.50 to 0.58% in the coals of Rungta-Amlai, 0.46–0.56% in Kotma, and 0.53–1.05% in Bijuri subbasins. Chemically, the coals belong to type High Volatile Symbol B 4 of Class Bituminous. The significant trace elements are V (20–400 ppm); Cu, Ni, Co (up to 300 ppm); Mn, Ba, Sr, Zr (up to 800 ppm); and La (up to 1200 ppm). The trace elements show a tendency to increase in proportion towards the eastern part of the coalfield.To the immediate east of the coalfield lies the Chirimiri coalfield, of which the compositional characteristics are also presented. These data clearly suggest that the coals of the Son valley are different from those of the other Gondwana basins, i.e., Mahanadi, Godavari, and Damodar valley basins.     

Petrological,chemical and depositional aspects of eastern Himalayan coals from elephant flat area,Kameng district,Arunachal Pradesh,India

The eastern Himalayan coals of India associated with Permian (Lower Gondwana) sediments in the Kameng district of Arunachal Pradesh have petrographic and chemical properties differing from Peninsular Permian coals.The coals are moderately to highly crushed and have reached a semianthracitic stage. Macerals are highly reflecting and homogenized. Vitrinite and inertinite exhibit a crushing effect in the form of criss-cross fissures and cracks. Exinite is unidentifiable and has attained an inertinitic reflectivity. The Kameng coals are of high rank with average fixed carbon 88.75% and volatile matter 13.75% on d.a.f. basis. The reflectance values (R_o-max 2.02–2.31% in oil) of these coals are quite high with marked anisotropy.It is inferred that these peculiar coal properties have been attained due to prolonged tectonic disturbance in the area during the later Himalayan orogeny. The coal characteristics suggest that these coals were formed in a humid tropical climate within a deltaic regime. The depositional site experienced occasional marine influx due to tectonically controlled subsidence during peat accumulation.     

Petrographic structure and composition of the Lower Carboniferous coal seams,western Donbas; their influence on chemical and technological properties of coals

The Lower Carboniferous coals which have been discovered and explored in the western Donbas since the war differ from those in the productive series of the old Donbas in age, petrographic composition and chemotechnological properties. From the Orel' river in the west to me Kal'mius river M the east the following have been recognized in the Lower Carboniferous: Visean coals of the sub-coal measures suite C² ₁(b), Viséan coals of the Samarsk suite C³ ₁ (c), and Namurian coals of suites C⁴ ₁ and C⁵ ₁ (d and c). The Lower Carboniferous coals over most of the western Donbas have (for a given rank) a higher yield of volatiles and primary tar, heat of combustion, sintering capacity, and hydrogen content. The rank increases to the northeast and produces a zonal disposition of coals of industrial type. The degree of coalification also increases with burial of the seams in the southwest limb of the Dneprovsk-Donets basin at depth. The basic aspect of metarnorphisrn is regional.' The petrographic structure and composition of the C³ ₁ suite coals in the western Donbas are responsible for their high chemical potential, whereby these coals are of great interest in the production of metallurgical coke. — C. E. Sears.     

Gondwana coals of Bhutan Himalaya - Occurrence,properties and petrographic characteristics

A narrow belt of highly inclined coal-bearing Gondwana strata occurs in the extreme south-eastern part of Bhutan Himalaya. Recently, a systematic survey was undertaken along this coal belt and coals of three areas were analyzed in detail for the evaluation of their physico-chemical properties and petrographic characteristics.The entire region is in the midst of the Great Himalayan orogenic belt, and the whole stratigraphic sequence underwent several diastrophic movements in the geological past. The massive effects of these orogenies is more pronounced in the coal beds of Gondwana sequence, and due to severe crushing and tectonic shearing these coals became powdery and flaky in nature. Significantly, the coals retained their pre-deformational rank exhibiting typical high-volatile, low-rank, bituminous characters, with mild caking propensities. Also these coals are markedly low in sulphur, phosphorus, chlorine and carbonate content like that of Peninsular Gondwana coals.Petrographic studies of these Bhutan coals revealed a close similarity with the eastern Raniganj coals (Upper Permian) of Peninsular India. The tectonic shearing and crushing of the coals are exhibited by the frequent presence of microfolding, microfaulting, and other compressional structures. However, the coals of all the three areas have shown a consistently low order of reflectance values.This typical retention of pre-deformational low-rank bituminous character is a significant feature of Bhutan coals. It shows that massive orogenic movements were only able to physically crush these coals but could not generate the requisite thermal regime to raise the rank of these coals.     

The role of coal petrographic characteristics in evaluating the non-coking nature of the coals of ramagundam and Kothagudem coalfields,Godavari Valley Basin,Andhra Pradesh,India

The maceral and microlithotype compositions of coals representative of the different coal seams of the Ramagundam and Kothagudem coalfields, Godavari Valley Basin, are compared with those of the Ib River, Talcher, South Karanpura, Hura, and Brahmani coalfields. The vitrite + clarite—“Intermidiates”—durite + fusite + shale (<20%) triangular diagram places these coals in the area of non-coking coals, clearly distinct from the coking and semi-coking coals. The vitrinite reflectance is low (R_ormoil^aver: 0.38–0.71%), far below the coking-coal range. Thus, based on petrographic composition and rank, these coals are of non-coking nature. A triangular diagram is proposed delineating the coking, semi-coking and non-coking coal areas for the Gondwana coals of India.     

Quality of selected coal seams from Indiana: implications for carbonization

The chemical properties of two high-volatile bituminous coals, the Danville Coal Member of the Dugger Formation and the Lower Block Coal Member of the Brazil Formation from southern Indiana, were compared to understand the differences in their coking behavior. It was determined that of the two, the Lower Block has better characteristics for coking. Observed factors that contribute to the differences in the coking behavior of the coals include carbon content, organic sulfur content, and oxygen/carbon (O/C) ratios. The Lower Block coal has greater carbon content than the Danville coal, leading to a lower O/C ratio, which is more favorable for coking. Organic sulfur content is higher in the Lower Block coal, and a strong correlation was found between organic sulfur and plasticity. The majority of the data for both seams plot in the Type III zone on a van Krevelen diagram, and several samples from the Lower Block coal plot into the Type II zone, suggesting a perhydrous character for those samples. This divergence in properties between the Lower Block and Danville coals may account for the superior coking behavior of the Lower Block coal.     

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.     

Origin and distribution of biomarkers in the sulphur rich Utrillas coal basin – Teruel mining district – Spain

The Utrillas coal facies are located in the Maestrazgo basin in NE Spain. This mining district of Teruel contains sub-bituminous deposits from the Middle Albian (Lower Cretaceous 105 Ma) in areas near a delta estuary with abundant sulphur. The high sulphur content is due to an influx of sulphate caused by the geological recycling of Triassic gypsum from the catchment area into the delta estuary. In some outcrops, the weathered coal reveals leonardite deposits. The depositional environment of the basin originated coals, some of which are currently mined. The organic matter of the coals has been the object of scattered reports. Studies have focused on bulk pyrolysis parameters and microscopic observation in Utrillas samples, as well as the inorganic and insoluble organic fraction.We analysed the organic soluble extract of the Utrillas coals using GC–MS in order to characterize their aliphatic, aromatic and organosulphur compounds. The biomarker distribution allowed us to recognize different inputs, assess their depositional palaeoenvironment and finally determine their degree of maturity. In particular, homologous series of hopanes related to eubacteria were present. Biomarkers characteristic of higher plant inputs were also widely distributed (e.g. phyllocladane or C₂₉ steranes). The presence of linear alkylbenzenes allowed us to recognize the palaeodepositional reducing environments where they were deposited. Specifically, thienylhopanes were associated with sulphur-reducing environments. Finally, the abundance of unsaturated biomarkers such as diacholestenes indicated low-maturity coals. Various aromatic ratios such as the methylphenanthrene index also suggested diagenesis in the initial stage.     

The application of FAMM (Fluorescence Alteration of Multiple Macerals) analyses for evaluating rank of Paraná Basin coals, Brazil

Combining vitrinite reflectance (VR) and fluorescence alteration of multiple macerals (FAMM) analyses provide insights into the chemical nature of vitrinites (i.e., perhydrous vs. orthohydrous vs. subhydrous compositions) in Permian Gondwana coals of the Paraná Basin, Brazil. The FAMM-derived equivalent VR (EqVR) values and relationships with VR can be determined according to calibration curves based largely on Permian Gondwana coals of eastern Australia.The analytical results indicate that vitrinites in the Paraná Basin coals studied generally range from orthohydrous to perhydrous, with interpreted VR suppression ranging up to 0.2% absolute for the most perhydrous case. The EqVR values of the Santa Catarina coals, which range from about 0.85% to 0.95% differ from VR values by about 0.10–0.15% absolute, potentially having significant implications on coal utilization.The causes of vitrinite reflectance suppression in the Paraná Basin coals are as yet poorly understood, but are likely to be related to a combination of factors.     

The rank evaluation of South Brazilian Gondwana coals on the basis of different chemical and physical parameters

Rank evaluation of South Brazilian Gondwana coals according to the American (American Society for Testing and Materials, ASTM) and German (Deutsche Industrie Normen, DIN) standard specifications or on the basis of Alpern's Universal Classification has too often led to conflicting results.When any attempt is made to determine the rank of Brazilian coals by using methods established for the Northern Hemisphere coals, two sorts of difficulties arise: namely, (1) the reflectence measurements do not indicate the real degree of coalification of the organic matter because of the liptinitic impregnations of the vitrinites, and (2) random reflectance values (R_ran, moisture, volatile-matter and carbon contents as well as the calorific value do not correlate when plotted on the ASTM and DIN classification schemes.In addition, when rank determinations are carried out by using fluorescence measurements and geochemical analyses the results are at variance in relation to those determined by the conventional chemical and physical parameters.It is suggested that the rank evaluation of South Brazilian coals is far more meaningful if carried out by reflectance measurements on vitrinites along with fluorescence measurements on sporinites, alginites and coal extracts.     

Processes controlling the composition of acid sulfate solutions evolved from coal

Leaching of a series of Appalachian coals by distilled water has been studied in laboratory reactors. From columns open to air at 25°C, leachates were produced containing typically about 0.2 M SO₄²⁻, 0.1 M total Fe and having pH < 2. Leachates contained high concentrations of toxic trace metals, including Be, Al, Cu and Cd. Concentrations of sulfate and Fe in leachates from different coals were similar and were not related to concentrations of total S in the coals. Saturation with respect to melanterite (FeSO₄·7H₂O) and a ferric oxyhydroxide phase was observed in most solutions. Leachates were undersaturated with respect to anhydrous ferric sulfate and Na-jarosite, but supersaturated with respect to K-jarosite, suggesting that none of these phases controlled solution composition. The ratio of total ferric Fe to total ferrous Fe normally exceeded unity. Accumulation of ferric Fe indicates either that its reaction with pyrite is inhibited in weathered coals, or that the coals contain pockets of oxidized pore fluid that are out of contact with pyrite. Release of Be correlated with release of Al, and release of Cu correlated with release of Fe. Reducing the temperature, lowering the partial pressure of oxygen or adding limestone retarded the release of pyrite oxidation products from the coals. Addition of limestone should be considered if it is necessary to control release of acid leachates from coal piles.     

Methane and carbon dioxide sorption on a set of coals from India

Complete sorption isotherm characteristics of methane and CO₂ were studied on fourteen sub-bituminous to high-volatile bituminous Indian Gondwana coals. The mean vitrinite reflectance values of the coal samples are within the range of 0.64% to 1.30% with varying maceral composition. All isotherms were conducted at 30 °C on dry, powdered coal samples up to a maximum experimental pressure of ~ 7.8 MPa and 5.8 MPa for methane and CO₂, respectively.The nature of the isotherms varied widely within the experimental pressure range with some of the samples remained under-saturated while the others attained saturation. The CO₂ to methane adsorption ratios decreased with the increase in experimental pressure and the overall variation was between 4:1 and 1.5:1 for most of the coals. For both methane and CO₂, the lower-ranked coal samples generally exhibited higher sorption affinity compared to the higher-ranked coals. However, sorption capacity indicates a U-shaped trend with rank. Significant hysteresis was observed between the ad/desorption isotherms for CO₂. However, with methane, hysteresis was either absent or insignificant. It was also observed that the coal maceral compositions had a significant impact on the sorption capacities for both methane and CO₂. Coals with higher vitrinite contents showed higher capacities while internite content indicated a negative impact on the sorption capacity.     

Petrographic characteristics and depositional conditions of Permian coals of Pench, Kanhan, and Tawa Valley Coalfields of Satpura Basin, Madhya Pradesh, India

This paper attempts to characterize the coals of Satpura Gondwana basin using a large number of pillar coal samples drawn from the working coal mines of Pench, Kanhan, and Tawa (Pathakhera) Valley Coalfields of this basin. This westernmost Gondwana basin of Peninsular India is graben/half-graben type and occupies an area of 12 000 km² with sedimentary fills (>5000 m) ranging in age from Permian to Cretaceous. The Barakar Formation (Permian) is exclusively coal-bearing with a total coal reserve of nearly 2000 Mt. The results show that the coals of this basin are equally rich in inertinite (22.8–58.7%, 24.5–62.0% mmf basis) and vitrinite (24.4–52.4%, 24.4–56.0% mmf basis). The concentration of liptinite ranges from 8.8% to 23.2% (9.0–26.0% mmf basis). The dominant microlithotypes of these coals are inertite and vitrite with comparatively low concentrations of vitrinertite and clarite. The vitrinite reflectance (Rom% values) suggests that the Pench Valley (0.30–0.58%) coals are subbituminous C to high volatile C bituminous in rank, while the Kanhan and Tawa Valley coals (0.52–0.92%) are subbituminous A to high volatile A bituminous in rank. The localized enhancement of rank in the latter two basins has been attributed to the extraneous heat flow from deep-seated igneous intrusions in the basin. The microlithotype composition of these coals is suggestive of their evolution in limno-telmatic zones, under fluvio-lacustrine control with the development of upper deltaic and lower deltaic conditions near the fresh water lacustrines. The floral input is characteristic of forest swamps with intermittent floods, leading to the development of reed moor and open moor facies, particularly in the Pench Valley basin. The Gelification Index (GI) and Tissue Preservation Index (TPI) are suggestive of terrestrial origin with high tree density. Further, moderately high GI and exceedingly high telovitrinite based TPI along with high ash content, particularly for the coals of Kanhan and Tawa Valley Coalfields, are indicative of the recurrence of drier conditions in the forested swamps. Furthermore, lateral variation in TPI values is indicative of increase in the rate of subsidence vis-à-vis depth of the basin from east to west (Pench to Tawa Valley Coalfield). The Ground Water Index (GWI) suggests that these coals have evolved in mires under ombotrophic to mesotrophic hydrological conditions. The Vegetation Index (VI) values are indicative of the dominance of herbaceous plants in the formation of Pench Valley coals and comparatively better forest input in the formation of Kanhan and Tawa Valley coals.     

Gondwana biostratigraphy of the Purnea Basin (eastern Bihar,India), and its correlation with Rajmahal and Bengal Gondwana basins

Integrated biostratigraphic studies are undertaken on the newly discovered Gondwana successions of Purnea Basin which have been recognized in the subsurface below the Neogene Siwalik sediments. The four exploratory wells, so far drilled in Purnea Basin, indicated the presence of thick Gondwana sussession (± 2450m) with varied lithological features. However, precise age of different Gondwanic lithounits of this basin and their correlation with standard Gondwana lithounits is poorly understood due to inadequate biostratigraphic data.Present biostratigraphic studies on the Gondwana successions in the exploratory wells of PRN-A, RSG-A, LHL-A and KRD-A enable recognition of fifteen Gondwanic palynological zones ranging in age from Early Permian (Asselian-Sakmarian) to Late Triassic (Carnian-Norian). Precise age for the Gondwanic palynological zones, recognized in the Purnea Basin and already established in other Indian Gondwana basins, are provided in the milieu of additional palynological data obtained from the Gondwana successions of this basin.The Lower Gondwana (Permian) palynofloras of Purnea Basin recorded from the Karandighi, Salmari, Katihar and Dinajpur formations resemble the palynological assemblages earlier recorded from the Talchir, Karharbari, Barakar and Raniganj formations respectively, and suggests the full development of lower Gondwana succession in this basin. The Upper Gondwana (Triassic) succession of this basin is marked by the Early and Middle to Late Triassic palynofloras that resemble Panchet and Supra-Panchet (Dubrajpur/Maleri Formation) palynological assemblages, and indicates the occurrence of complete Upper Gondwana succession also in the Purnea Basin.The lithological and biostratigraphic attributes of Gondwana sediments from Purnea, Rajmahal and western parts of Bengal Basin (Galsi Basin) are almost similar and provides strong evidences about the existence of a distinct N-S trending Gondwana Graben, referred as the Purnea-Rajmahal-Galsi Gondwana Graben. Newly acquired biostratigraphic data from the Gondwana sediments of CHK-A, MNG-A and PLS-A wells from central part of Bengal Basin and Bouguer anomaly data suggest that these wells fall in a separate NE-SW trending graben of “Chandkuri-Palasi-Bogra Gondwana Graben”. Although, the post-Gondwana latest Jurassic-Early Cretaceous Rajmahal Traps and and intertrappean beds succeed the Upper Gondwana successions in Rajmahal, Galsi and Chandkuri-Palasi Gondwana basins, but not recorded in the drilled wells of Purnea Basin, instead succeeded by the Neogene Siwalik sediments.     

Sulphur and carbon isotopic composition of power supply coals in the Pannonian Basin, Hungary

The present work is an attempt to establish the stable isotope database for Mesozoic to Tertiary coals from the Pannonian Basin, Hungary. Maceral composition, proximate analysis, sulphur form, sulphur isotopes (organic and pyritic), and carbon isotopes were determined. This database supports the assessment of the environmental risks associated with energy generation, the characterization of the formation and the distribution of sulphur in the coals used.The maceral composition, the sulphur composition, the C, S isotopic signatures, and some of the geological evidences published earlier show that the majority of these coals were deposited in freshwater and brackish water environments, despite the relatively high average sulphur content. However, the Upper Cretaceous, Eocene, and Lower Miocene formations also contain coal seams of marine origin, as indicated by their maceral composition and sulphur and carbon chemistry.The majority of the sulphur in these coals occurs in the organic form. All studied sulphur phases are relatively rich in ³⁴S isotopes (δ³⁴S_organic = + 12.74‰, δ³⁴S_pyrite = + 10.06‰, on average). This indicates that marine bacterial sulphate reduction played a minor role in their formation, in the sense that isotopic fractionation was limited. It seems that the interstitial spaces of the peat closed rapidly during early diagenesis due to a regime of high depositional rate, leading to a relative enrichment of the heavy sulphur isotopes.     

Upper Triassic turbidites of the northern Tethyan Himalaya (Langjiexue Group): The terminal of a sediment-routing system sourced in the Gondwanide Orogen

The Upper Triassic Langjiexue Group, exposed south of the Yarlung-Zangbo suture zone in south Tibet, shows sedimentary features different from typical Tethyan Himalayan successions, and its origin is controversial. In this article we combine field observations with paleocurrent, petrologic, geochronological and isotopic data to determine the provenance of Langjiexue sandstones. These middle to distal deep-sea-fan turbidites are crosscut by Lower Cretaceous diabase sills and dikes generated during rifting of India from Gondwana, indicating that the Langjiexue Group was originally deposited along or adjacent to the northern passive continental margin of India. Flute casts at the base of turbidite beds indicate mostly WNW-ward paleocurrents, pointing to provenance from a source located east of the depositional area. Common volcanic fragments and plagioclase grains together with a cluster of 400–200-Ma-aged magmatic zircons with uniform ε_Hf(t) values from − 5 to + 10 are incompatible with any nearby sources, including the Qiantang Block, the Lhasa Block or the India subcontinent, and indicate instead supply from a long-lived magmatic-arc terrane. Considering what is known about Late Triassic paleogeography, a plausible source for Langjiexue sediments is represented by the Gondwanide Orogen, generated during subduction of the pan-Pacific oceanic lithosphere beneath southeastern Gondwana. This scenario is supported by the age range and Hf isotopic signatures of Late Paleozoic–Early Mesozoic zircons contained in Langjiexue turbidites as in coeval turbidites exposed in western Myanmar. New data are needed to confirm/falsify the existence of a thousand-km-long sediment-routing system similar to the modern Amazon, which – sourced in a cordillera-type orogen rising along the southeastern margin of Gondwana – crossed an entire continent to feed turbiditic fans now exposed from western Myanmar to the northern Tethys Himalaya.     

Ge-bearing coals of the Luzanovka Graben, Pavlovka brown coal deposit, southern Primorye

Results of the study of a new Ge-bearing area of the Pavlovka brown coal deposit are presented. Ge is accumulated in bed III₂ lying at the bottom of the Late Paleogene-Early Neogene coal-bearing sequence adjacent to the Middle Paleozoic granite basement. The Ge content in coals and coal-bearing rocks varies in different sections from 10 to 200–250 ppm, reaching up to 500–600 ppm in the highest-grade lower part of the bed. The metalliferous area reveals a geochemical zoning: complex Ge-Mo-W anomalies subsequently grades along the depth and strike into Mo-W and W anomalies. Orebodies, like those at many Ge-bearing coal deposits, are concentric in plan and dome-shaped in cross-section. Coals in their central parts, in addition to Ge, W, and Mo, are enriched in U, As, Be, Ag, and Au. Distribution of Ge and other trace elements in the metalliferous sequence and products of gravity separation of Ge-bearing coals is studied. These data indicate that most elements (W, Mo, U, As, Be) concentrated like Ge in the Ge-bearing bed relative to background values are restricted to the organic matter of coals. The electron microscopic study shows that Ge-bearing coals contain native metals and intermetallic compounds in association with carbonates, sulfides, and halogenides. Coal inclusions in the metalliferous and barren areas of the molasse section strongly differ in contents of Ge and associated trace elements. Ge was accumulated in the coals in the course of the interaction of ascending metalliferous solutions with organic matter of the buried peat bogs in Late Miocene. The solutions were presumably represented by N₂-bearing thermal waters (contaminated by volcanogenic CO₂) that are typical of granite terranes.