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The health risks associated with exposure to respirable dust in coal mines have been attracted much attention by an increasing number of researchers. However, the accurate identification of potentially hazardous agents in respirable dusts and the evaluation of the potential health risks arising from it still remains controversial to varying degrees. A comprehensive understanding of the physicochemical properties of respirable dust is a prerequisite and an important basis for resolving this controversy. Therefore, in this study, the particle size distribution and morphology, pore structure, mineralogical and geochemical patterns, and oxidative potential (OP) of respirable coal mine dust were comprehensively investigated. Stepwise multiple linear regression was employed to identify dust components driving OP, such as anatase, tobelite, quartz, and ankerite, in respirable coal mine dust, along with Na, Ni, Se, W, and As. On this basis, we performed a single-factor risk prediction for different coal mines by considering factors that may impact miners' health, with the analyses yielding somewhat contradictory results. Therefore, a multifactor integrated prediction model is proposed using an entropy-based technique for order preference by similarity to the ideal solution to categorize coal mines in the study area into three risk categories, high-, medium-, and low-risk dust mines, which is important for the hierarchical classification and control of coal mines and for formulating appropriate dust prevention and control measures. [Display omitted] • A comprehensive investigation of the physicochemical and oxidative potential characteristics of respirable coal mine dust (RD). • Stepwise multiple linear regression was employed to identify the potentially hazardous agents of RD. • The TOPSIS was used to comprehensively evaluate health risks in various coal mines and sites within those mines. [ABSTRACT FROM AUTHOR]

Abstract This paper investigates the mineralogy of coal and non-coal samples from the Haerjiao exploration area in the Jimunai depression, Xinjiang Uygur Autonomous Region, northwestern China, using X-ray diffraction (XRD), optical microscopy and scanning electron microscopy with an energy dispersive X-ray spectrometer (SEM-EDX). The minerals in the anthracite proximal to the igneous intrusions are represented by the occurrence of chlorite, muscovite, and illite, which are absent in the semianthracite distal to the igneous intrusions. Kaolinite, the dominant mineral in the semianthracite, decreases in abundance or even disappears in the anthracite. Muscovite and illite in the anthracite are interpreted to result from the alteration of the kaolinite precursor and possibly formed by the interaction of kaolinite and elements (e.g., K, Fe, and Mg) from igneous hydrothermal solutions. The formation of chlorite is the result of the transformation of kaolinite due to the interaction of kaolinite with Fe-Mg-rich solutions during the diagenetic stage and the direct epigenetic precipitation from Fe-Mg-rich igneous siliceous hydrothermal fluids. Calcite, ankerite, and sulfide minerals resulted from epigenetic precipitation from hydrothermal fluids. Cleat/fracture mineralization indicates that the Fe-Mg-rich hydrothermal fluid from which chlorite precipitated was introduced earlier than the Ca-rich fluid from which calcite precipitated. The injection of hydrothermal solutions that formed sulfide minerals occurred at the latest stage. Highlights • Igneous intrusions cause variations of coal rank and minerals. • Chlorite was formed by the transformation of kaolinite and direct precipitation from hydrothermal fluids. • Calcite and sulfides are mainly formed by the epigenetic solution precipitation. • Fe-Mg-rich hydrothermal fluid was earlier introduced than Ca-rich fluid. [ABSTRACT FROM AUTHOR]

This research focuses on the potential use of fly ash (WAf) from a Chinese pulverized-coal combustion (PCC) power plant for manufacturing foam glass. The influences of fly ash properties, fly ash/recycled glass proportion in the raw materials, addition of fluxing and foaming agent, firing temperature, and residence time at the peak temperature on the final properties (apparent density, compressing strength and leachable potential of major and trace elements) of the foam specimens are investigated. The optimal foaming products were obtained consuming up to 33.3–43.3% fly ash, adding 9–11% Na 2 CO 3 fluxing agent and 0.5% SiC foaming agent, firing at 865–915 °C during 15 min residence time at the peak temperature. The obtained fly ash-based product revealed comparable compressive strength but slightly higher densities than commercial foam glass, with low CO 2 emissions and low leachable potential for environmentally relevant trace elements within the limits for inert/no-hazardous material established by the European Council Decision 2003/33/EC for land waste disposal. The large porosity of the foam glass indicates a high potential of thermal and acoustic insulation. The foaming behavior and the final properties the foam glass are strongly influenced by properties of fly ash (mainly fluxing temperature and organic C content), fly ash/recycled glass proportion in the raw materials, addition of Na 2 CO 3 fluxing agent and SiC foaming agent, firing temperature, and residence time at the peak temperature. The low C content and high refractory character of WAf give rise to poor foaming of the specimens when only fly ash and Na 2 CO 3 mixtures are used. The consumption of relatively high proportions of recycled glass and SiC is essential to produce foaming. [ABSTRACT FROM AUTHOR]

This paper investigates the mineralogy and geochemistry of four coal beds (WJB-6, WJB-7, FHS-23 and FHS-27 Coals) of the Late Permian in the Zhina Coalfield, western Guizhou Province, China. The investigated coals reach the semianthracite -anthracite coal rank and have super-low to low ash yields. The sulfur contents vary considerably through coal sections and are mostly in the range of medium-high sulfur coal. The mineral assemblage present in the FHS-23 and FHS-27 Coals is mainly made up of pyrite and rectorite; the WJB-6 and WJB-7 Coals have different mineralogy, with kaolinite and rectorite dominant in the former as well as quartz and rectorite in the latter. These coals contain high concentrations of Nb and Ta, but Li is only enriched in the WJB-6 Coal. Rectorite and anatase in these coals are important hosting phases of Nb and Ta while kaolinite, and to a lesser extent chamosite in the WJB-6 Coal, are dominant carriers for the elevated Li concentration. The terrigenous material input, the marine influence and the effect of circulating hydrothermal solution are the pivotal geological factors causing geochemical anomalies in coals investigated. The high-sulfur coals were subjected to an enhanced marine influence in the depositional environment, as well as to a higher terrigenous influx, when compared with the medium-sulfur and low-sulfur coals, resulting in higher concentrations of S-Fe-As-Mo-U-Hg in the former coals than in the latter ones. The anomalous enrichment of Nb and Ta in these coals, as well as of Li in the WJB-6 Coal, is the result of the contributions from ascending hydrothermal solutions, although source rocks (e.g., high-Ti basalt) may provide relatively high background abundances of Nb, Ta and Li. [ABSTRACT FROM AUTHOR]

The coals from the Jungar Coalfield, Inner Mongolia, China, have been found to be enriched in Ga and Li. These are valuable metals that are potentially recoverable from coals and/or coal combustion residues. Based on fifteen roof/floor/parting samples collected from one borehole and one hundred and forty one bulk coal samples collected from three boreholes in the Buertaohai-Tianjiashipan coal mining district, Jungar Coalfield, this paper reports new data on the mineral compositions and geochemical characteristics of the Jungar Li-Ga-rich coals, and provides new evidence for the origin and mode of occurrence of Al, Ga and Li in these coals. The main mineral phases occurring in the coals are kaolinite, boehmite, calcite, with small proportions of quartz, pyrite, ankerite, siderite, and trace amounts of microcline and rectorite. An unusual mineral phase, svanbergite (SrAl 3 (PO 4 )(SO 4 )(OH) 6 ) also occurs as a main mineral constituent in the studied coals. The mineral phases in the roof/floor/parting samples are dominantly kaolinite, with a small proportion of quartz. Kaolinite is of both terrigenous and authigenic origin, which were possibly derived from terrigenous Yinshan Oldland sediment-source region and/or from recrystallization during the coal formation process. Boehmite and svanbergite are primarily of authigenic origin, and were dominantly derived from the weathered bauxite sediment-source region. Calcite may have formed by dissolution of limestone layers close to the margin of coal basin and subsequent deposition of the Ca or Mg-rich carbonates in the cells/fractures of the coal seams. Sulfide minerals in fractures may have been precipitated from epithermal fluids. Rectorite was probably formed by the reaction of kaolinite with epigenetic low-temperature hydrothermal fluids during diagenesis. Compared to common Chinese and worldwide coals, the studied Jungar coals are much more enriched in Al (4.4–6.1%), Li (70–79 mg/kg), and Ga (14–19 mg/kg). Titanium, P, Sr, Zr, Nb, Th, Ta, Hf, and rare earth elements (REEs) are also enriched in the studied coals to some extent. Aluminum in the coals mainly occurs in the form of kaolinite and boehmite, whereas, lithium may be associated with aluminosilicate minerals (kaolinite and illite if present) as well as svanbergite. Gallium principally occurs in kaolinite, and to a lesser extent, svanbergite. Strontium, P, and LREEs (La, Ce, and Rr, Nd and Sm) mainly present in svanbergite. The source of Li and Ga in Jungar coals is most likely from the Yinshan Oldland region, but there is also a possibility of migration from bauxite of the Benxi formation. [ABSTRACT FROM AUTHOR]

This paper investigates the mineralogical and geochemical compositions of the Late Permian coals in the Liulong Mine, Liuzhi Coalfield, Western Guizhou Province, China, by using XRD, SEM-EDX, ICP-AES and ICP-MS. Both the No.3 and No.7 Coals are classified as low volatile bituminous coal. However, the No.3 Coal is a medium-ash (29.8% on average) and high-sulfur (4.76% on average) coal while the No.7 Coal is a low-ash (12.4% on average) and medium-sulfur (2.16% on average) coal. Major minerals in both coal seams include quartz, pyrite, marcasite, kaolinite, calcite, and to a lesser extent, gypsum and anatase. Illite, chlorite, rectorite, albite, ankerite and siderotil are only present in the No.3 Coal. The No.3 Coal contains higher elemental concentrations than the No.7 Coal probably due to the higher mineral contents in the No.3 Coal, and is enriched in Nb and Ta, and to a lesser extent in K, Ti, Li, V, Co, Cu, Sr, Zr, Mo and Ba. The mineralogical and geochemical data presented in this study have shown that the No.3 Coal was formed under a higher degree of marine-influenced coal-forming environment than the No.7 Coal. However, the both Coals have the Kangdian Upland (made of mafic igneous rocks, such as basalt rocks) as sediment-source region like other coals from Guizhou Province. Three geological factors control the geochemical patterns of the No.3 and No.7 Coals, namely: (1) the high detrital input in the No.3 Coal causing high ash yields; (2) the sediment-source region (Kangdian Upland basalt) causing high Ti, Nb and Ta contents, and a minor proportion of Co, Cr, V and Cu, when combined with the high detrital input in the No.3 Coal; (3) the higher degree of marine influenced depositional environment in the No.3 Coal causing a high S, Sr and Ba contents. [ABSTRACT FROM AUTHOR]

The present study investigates the geochemical characteristics of the flue gas desulfurization gypsum (FGD Gp) generated from a pulverized-coal combustion (PCC) power plant in Xinjiang, Northwest China, with special emphasis on manufacturing fire-resistant panels using this FGD Gp as well as the fly ash collected from the same power plant. The physical, mechanical and insulating properties of the manufactured panels are also determined. The FGD Gp is characterized by low trace element concentration and low leachable potential for environment-concerned trace elements, indicating it can be reused with low environmental implication. Fire-resistant panels were successfully made from pure FGD Gp, pure commercial gypsum (CGp) and different FGD Gp/fly ash and CGp/fly ash mixtures. With the same gypsum/fly ash proportion, the FGD Gp/fly ash panels present relatively lower density, lower water absorption and lower mechanical strength, but higher moisture contents and better insulating capacities than the CGp/fly ash panels. The pure FGD Gp panel presents the best insulating capacity (52 min), much higher than that of the pure CGp panel (42.8 min). The mechanical and insulating properties of the panels are reduced with the increasing of fly ash proportion in the mixtures, but even prepared with 80% fly ash, the manufactured panels can still be used as benign fire-resistant panels with no significantly physico-chemical, and mechanical limitations. Therefore, manufacture of fire-resistant panels from FGD-Gp and fly ash is a very promising application for these coal combustion by-products which are substantially being generated in large amounts from Xinjiang power plants. The manufactured fire-resistant panels can be used in large amount as insulating construction and building materials with low environmental implication and high economic value. [ABSTRACT FROM AUTHOR]

Oxidative potential (OP) is considered to be an efficient indicator of particulate matter (PM) to induce oxidative stress in the lungs and is increasingly considered to be a relevant health metric. In this study, two complementary OP assays were deployed, including dithiothreitol (DTT) and ascorbic acid (AA) assays, to investigate the potential toxicity (as generators of oxidative stress) of respirable fractions (DD4, < 4 μm) of deposited dust (DD500, < 500 μm) in underground low-S and low-pyrite coal mines in Henan Province, Central China. The OPDTT of DD4 is higher than that reported for other types of atmospheric PM, whereas the OPAA of DD4 is similar and/or slightly higher. Cross-correlation and multilinear regression analyses are applied using datasets of major mineral and geochemical patterns in the DD4 samples and the respective OP values to identify the major drivers for OP in respirable coal dust. Thereafter, the patterns of DD4 are compared with those of DD500 and the parent coals to determine the sources of OP-relevant substances. OPDTT is mainly governed by some trace elements (Sb, As, Li, B, Sr, and Pb) and minor minerals (anatase, quartz, siderite), and their synergistic effect may be one of the reasons for the high DTT consumption. For OPAA, quartz, total clay (sum of illite, kaolinite, tobelite, and clinochlore) and Ni, Cr, Co, Si, and S, play an important role in regulating the OPAA of pyrite-free DD4 samples. These OP-relevant substances have three sources: coal dust, which has a similar composition in DD4, DD500, and the parent coal (such as siderite and its associated elements); gangue dust, which does not occur in the parent coal but is widely detected in DD4 and DD500 (such as quartz, kaolinite, and relevant elements); and cement dust (from gunite galleries), which is mainly calcite- and calcite-associated elements. • A study of the mineralogy, geochemistry and OP of deposited dust, respirable dust and coal in underground coal mines. • OPDTT of size-segregated respirable dust (DD4) is mainly governed by anatase, siderite, quartz, and Sb, As, Li, B, Sr, Pb. • OPAA of DD4 is regulated by anatase, tobelite, kaolinite, and total clay, as well as Ni, Cr, Co, Si, and S. • The parent coal dust, gangue dust, and cement dust are the primarily source of these hazardous materials. [ABSTRACT FROM AUTHOR]

This study summarizes the results of geological, petrographical, geochemical, and mineralogical analyses performed to determine the geological controls on coal quality of the Yili Basin in Xinjiang province, northwest China. Forty-eight coal samples were collected from boreholes Q12ZK01 and Z40ZK1, and Piliqing and Musixiang coal mines. The difference in base subsidence rate between the coal-bearing strata Badaowan and the Xishanyao Formations determines these differences of depositional environments, swamp groundwater table, and degree of terrigenous supply. These factors may further cause the difference in coal quality. The vitrinite contents, ash yields, volatile matter yields, total mineral contents, and most element contents are higher in coals of the Badaowan Formation from the Q12ZK01 and the Musixiang mine than those of the Xishanyao Formation from the Piliqing mine and the Z40ZK1. The high volatile matter yields of the coals in the Badaowan Formation, relative to those in the Xishanyao Formation, may be due to higher content of vitrinite that contains more volatile matters. In comparison with the average concentrations for Chinese and worldwide coals, the Yili coals are enriched mainly in Ca, Na, Mg, Mn, Co, Sr, Ba, and W, but the other elements are depleted in the Yili coals. Elements including Si, Al, K, Li, Ti, Cr, Cu, Rb, Zr, Pb, and some REE (La, Ce, Pr, Nd, Sm) are predominantly associated with aluminosilicate minerals. Iron, Mg, and Mn in the coals of the Musixiang mine and Z40ZK1 are associated mainly with carbonate minerals. Sulfur, Co, and Ni in the Musixiang mine coals, and B in the coals of Q12ZK01 and the Z40ZK1 mainly show an organic affinity. Sodium in the Musixiang mine coals may occur in the brines. [ABSTRACT FROM AUTHOR]

Abstract: The Yimin Ge-coal deposit, located in the Yimin coalfield, Inner Mongolia, is the third largest Ge-rich coal deposit in China just after the Lincang and Wulantuga Ge-coal deposits. Based on the coal and non-coal samples recently collected from the Wumuchang coal mining district in the Yimin Ge-coal deposit, this paper reports some new data on the mineralogical and geochemical characteristics of the Yimin high-Ge coals, and provides some new evidence for the possible mode of Ge enrichment in the Yimin coals. Mineralogical analyses were performed by means of Powder X-ray diffraction (XRD). Major and trace element concentrations were determined by inductively coupled plasma atomic-emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS), respectively. Element affinities were determined by Pearson's correlation analysis. The studied coals fall within the coal rank between sub-bituminous A and high volatile bituminous C, with relatively high moisture content, high volatile matter yield and low to medium ash yield. Quartz and kaolinite are the main mineral matters in the Yimin coals, with small amounts of pyrite and traces of microcline. Common pyrite and As-bearing pyrite occurring in the Yimin coals show an epigenetic origin. The epigenetic precipitation of kaolinite, quartz and As-rich pyrite (with Ge, and other trace elements) in the Yimin coal fractures may be caused by activities of both hydrothermal and low temperature fluids. Compared to common Chinese and worldwide coals, the Yimin coals are markedly enriched in Ge (43mg/kg), As (155mg/kg), and W (9.84mg/kg) and slightly enriched in Pb (22mg/kg) and Hg (0.24mg/kg). Most of the elements (e.g. Al, K, Sc, Ti, V, Cu, Ga, Sn, Th and REEs) in the studied coals present an aluminosilicate affinity as deduced from their obvious positive correlation with Al and ash yields. High correlation coefficients of As and Hg with Fe and S indicate a sulfide affinity of these elements in the Yimin coals. Germanium, B, Mo, and W in the studied coals show an organic affinity and a partial sulfur affinity as deduced from their negative correlation with Al and positive correlation with S, respectively. The preliminary and possible model for Ge enrichment in the Yimin Ge-coal deposit was that Ge was carried by hydrothermal fluids and then these fluids were incorporated in the water existing in the upper porous conglomerates and percolate in the top of the coal seam, where Ge was trapped by organic matter and finally enriched in an early diagenetic stage (humification–gelification). [Copyright &y& Elsevier]

Highlights: [•] Large amounts of coal fly ashes generated from power plants in Xinjiang, Northwest China. [•] Synthesis of high value-added zeolite from fly ash by KOH direct conversion method. [•] Utilize synthetic merlinoite product as efficient slow release potassic fertilizer. [•] Application potential of merlinoite for soil reclamation around opencast coal mines. [Copyright &y& Elsevier]

This study systematically investigates the mineralogical and geochemical variations in parent coal, coal gangue (roof, parting, and floor), deposited coal mine dust (DD), and respirable fractions of DD (RD) in an underground coal mine using the blasting mining method in China to evaluate the major sources of DD. The emission of dust in this study is affected by coal gangue sources during the mining process, which causes different geochemical patterns in the DD samples. Moreover, weathering of the cement gunite walls plays an important role in the enrichment of specific elements in the DD from air uptake and air out galleries. Furthermore, the spatial variation in RD characteristics, including mineralogy, geochemistry, and oxidative potential (OP), is discussed, with emphasis on the major health-relevant species and elements. Organic species from coal dust seem to be the essential components contributing to OP rather than metals, although some metals (e.g., Cr, Co, Ge, Se, Zn, Ba, Rb, Cs, Sn, and Pb) influence OP to some degree. [Display omitted] • Deposited coal mine dust, parent coal, and gangue in an underground coal mine using blasting mining method were studied. • Gangue and cement dust mixed into coal dust result in the enrichment of abundant elements. • The primary species driving the oxidative potential are site-dependent. • Organic species, quartz, calcite, and Cr, Co, Ge, Zn, Ba, Rb are highly correlated with toxicity. [ABSTRACT FROM AUTHOR]

Abstract: The mineralogical and geochemical characteristics of feed coals and their combustion by-products (fly ash and slag) from Hongyanchi (HONG) and Weihuliang (WEI) coal-fired power plants in Xinjiang Province, Northwest China, were investigated. The enrichment and partitioning behaviour, as well as the leaching potential of the major and trace elements in these combustion by-products were evaluated. Three feed coals from the two power plants (HC, WC1, and WC2) were characterised by medium-moisture contents, low- to medium-ash yields, high volatile matters, and low-S contents as well as low-mineral contents. Except B, Sr, and Ba in WC1 feed coal; P, Ti, V, Cr, Mn, Cu, Zn, Rb, and Ba in WC2 feed coal; and Ti, Mn, Cu, Zn, Rb, Sr, and Ba in the HC feed coal, most major and trace element concentrations were low compared with other Chinese coals and coals worldwide. Most trace element concentrations in the studied fly ashes (HA, WAf, and WAc) were even lower than their minimum and/or 25th percentile (P25) values reported for EU fly ashes, as were the element concentrations in the fly ash leachates. The studied fly ashes were all classified as type F fly ashes, with high glass contents as well as high SiO2/Al2O3 ratios in the glass matrix. Through enrichment factors, mass balance, and partitioning of elements, S, F, Cl, Hg, and B were highly volatile in both PCC plants. Tin, As, Se, Cu, and Zn were also moderately volatile, and they were enriched in fly ashes mainly by volatilisation/condensation. Iron and Mn were slightly enriched in slags, probably due to the high density of Fe–Mn-bearing phases. In the light of the above-mentioned properties, fly ashes and slags from the two power plants in Xinjiang will have a very high potential for a variety of uses, with very low environmental limitations. In summary, this study is demonstrating the high quality of Xinjiang coals with enormous coal reserves, and also the high quality of the combustion by-products that will be produced also in very high amounts in the near future. Major focus is on trace elements. [Copyright &y& Elsevier]

Abstract: The mineralogical and geochemical characteristics of the Late Permian Huayingshan coals, partings, roof and floor strata, as well as lutitic rocks from the Longtan Formation, in Sichuan Province, southwestern China, were investigated in this study. The Huayingshan low volatile bituminous coals are characterized by relatively high mineral contents (mainly kaolinite, quartz, pyrite, and calcite). The concentrations of most trace elements are relatively high compared with other Chinese and world coals. The coals and associated strata show similar element affinities: Al, Ti, Li, Ta, Th, Ga, U, Sn, Sc, Cr, Cu, Rb, Co, and Se probably have an aluminosilicate affinity; Zr, Nb, Hf, Y, REEs, and U probably result from the occurrence of heavy minerals such as zircon; S, Fe, W, and Rb mainly have a sulfide affinity; Ca, Sr, and Mn mainly have an carbonate affinity. The high enrichment in the Huayingshan coal of Zr, Nb, Hf, REEs, Ta, Ga, and Th is caused by a geochemical anomaly in the source of this coal''s detrital material (and probably also by input of volcanic ash), which is influenced by the alkaline volcanic magmas of the Emeishan basalt. The Zr/Hf, Zr/Nb, Zr/La and Zr/Th ratios support the volcanic origin of such a geochemical anomaly. [Copyright &y& Elsevier]

Abstract: The Lincang (Yunnan Province, Southwest China) and Wulantuga (Inner Mongolia, Northeast China) coal deposits are known because of the high-Ge content. These coals have also a high concentration of a number of other elements. To determine the mode of occurrence of the enriched elements in both coals, six density fractions from<1.43 to>2.8g/cm3 were obtained from two representative samples using heavy-liquids. A number of peculiar geochemical patterns characterize these high-Ge coals. Thus, the results of the chemical analysis of these density fractions showed that both coals (very distant and of a different geological age) are highly enriched (compared with the usual worldwide coal concentration ranges) in Ge, As, Sb, W, Be, and Tl. This may be due to similar geochemistry of hydrothermal fluids influencing the Earth Crust in these regions of China. Moreover, Wulantuga coal (Early Cretaceous subbituminous coal) is also enriched in Ca, Mg, and Na, and Lincang coal (Neogene subbituminous coal) in K, Rb, Nb, Mo, Sn, Cs, and U. A group of elements consisting of Ge, W, B, Nb, and Sb mostly occur with an organic affinity in both coals. Additionally, Be, U, and Mo (and partially Mn and Zn) in Lincang, and Na and Mg in Wulantuga occur also with a major organic affinity. Both coals have sulfide–arsenide mineral assemblages (Fe, S, As, Sn, and Pb, and in addition to Tl, Ta, and Cs in the Lincang coal). The occurrence of Al, P, Li, Sc, Ti, V, Cr, and Zr in both coals, and Ba in Lincang, are associated with the mineral assemblage of silico-aluminates and minor heavy minerals. Furthermore, P, Na, Li, Sc, Ti, Ga, Rb, Zr, Cr, Ba, Th, and LREE (La, Ce, Pr, Nd, and Gd) in Lincang are associated with mineral assemblages of phosphates and minor heavy minerals. The two later mineral assemblages are derived from the occurrence of detrital minerals. Finally, the two coal samples have also the sulfate mineral assemblage (Ca and Sr) that probably occur as a consequence of a diagenetic oxidation and alteration of the coal seams. The enrichment of Ge in coal occurred when the organic matter was still reactive to trap Ge, but several features indicate that the enrichment was diagenetic. [Copyright &y& Elsevier]

Abstract: The Zhundong coalfield is a very large coal deposit, currently under exploration, and promises to be an important coal mining resource in Western China. The coal reserves amount to 164Gt. At Xiheishan and Wucaiwan, the coal-bearing units are the Badaowan (Lower Jurassic) and, especially, the Xishanyao formations (Middle Jurassic). These contain from one to 31 coal seams (one to 10 workable coals reaching the rank of high volatile A bituminous) with an accumulated workable coal thickness of 20–87m. These recently explored coal reserves are of a high quality and are characterized by low ash, aluminum, iron, sulfur, and trace element contents. The minerals present in this coal are mainly quartz, kaolinite, siderite, and pyrite. The trace element contents in both Xiheishan and Wucaiwan coals are much lower when compared with the usual concentration ranges present in Chinese coals, with the exception of Ba and Sr. Thus, Ba contents in Xiheishan coal are higher than Swaine''s worldwide concentration range. A large number of elements have mainly aluminosilicate affinity, and occur in clay and other detrital coal minerals. Ca and Mn have mainly carbonate affinity; Fe and S have mainly sulphide affinity in Wuchaiwan coal. In Xiheishan, Fe, Mn and Mg have mainly carbonate affinity (siderite), and probably, B, Co, Ni and S have an organic affinity. Thus, the Zhundong coalfield contains coal with a very high quality and very low levels of impurities. The very low ash yields, S, Fe, and trace element contents may be attributed to the sedimentological setting, with intensive peat bog aggradation in a very shallow lake environment with a low detrital supply. The very low sulfur content, the relatively high Ba-sulfate (barite) content and the high siderite occurrence in Xiheishan coal (in contrast to the pyrite occurrence in Wucaiwan coal) may be attributed to the rapid aggradation of peat with the consequent oxidation and leaching of minerals, elements, and degradation of organic components. Under this scenario, sulfate is trapped by the continuous precipitation and accumulation of barium sulfate (very low soluble). [Copyright &y& Elsevier]

Abstract: The geological and geochemical controls of the Ge distribution in the Cretaceous Wulantuga high-Germanium coal deposit in the Shengli coal field, Inner Mongolia are investigated. This paper focuses mainly on the spatial distribution of the Ge contents in coal. The high-Ge coals mainly occur in three splits of the #6 coal in the southwestern part of the Shengli coal field. Mean germanium contents in the coal range from 32 to 820 μg/g, with a mean value of 137 μg/g, on a bulk coal basis (mean of 939 coal samples from 75 boreholes in the #6 coal seam) in an area of 2.2 km2. The highest Ge content occurs SW of #6 coal seam, close to the margins of the coal basin, decreasing with a fan-shaped trend towards NW, the direction of the coal basin. There is an negative correlation between the mean Ge content and the thickness of the coal seam. Different distribution patterns of Ge content were found in vertical profiles. High Ge concentrations may occur in the middle parts of coal seams, at the bottom and/or the top of thick coal seams and inconspicuous variation. A major organic affinity was determined for Ge, with a special enriched in the banded bright and semibright coal. The high-Ge coals and the coalified wood in the sandstone overlaying the #6-1 coal highly enriched in Ge, As, Sb, W, Cs, Tl, Be, and Hg. The Late Jurassic silicified volcanic rocks in the NW of the Ge coal deposit relatively high enriched in Ge, Ga, Sb, As, Cs, Be, Ge and Hg. The correlation coefficients among the elements enriched showed marked variations at close sites in this deposit, suggesting a possible diagenetic origin of the geochemical anomaly. The main Ge anomaly was attributed to early Cretaceous hydrothermal fluids circulating through the fault systems and porous volcanic rocs, probably from the subjacent granitoid rocks. The fault systems, the porous coarse clastic rocks overlying coal seam and the lithotype of coal played an important role in the transport and trapping of Ge. A main diagenetic origin (overlapping a slight synsedimentary accumulation) is deduced for the Ge anomaly. [Copyright &y& Elsevier]

Abstract: This paper deals with the study of the Late Permian coal deposits from Chongqing and south-eastern Hubei mining districts and of the Late Triassic coal deposits from Chongqing mining district. The Late Permian coals are characterized by relatively high amount of sulphide, sulphate and carbonate minerals and by a high total content of trace elements (with respect to the Late Triassic coals) due to the marine influence on the depositional environment. The Late Permian Chongqing and the southeastern Hubei coals showed similar geochemistry and mineralogy. However, there were some differences due to the different source rock and magmatic influence on Hubei coals. The concentrations of most trace elements in the Late Triassic coal were relatively low when compared with the usual range of the worldwide concentrations. By contrast, the contents of Ta, Se, Nb, Sc, Hf, Tl, Bi, Cu, V and Zn in the Late Permian Chongqing and Southeastern Hubei coals were higher than the usual range. Differences in occurrence of major and trace elements were found between Late Permian Hubei and Chongqing coals. Thus, most of the trace elements investigated presented an aluminosilicate association, followed by sulphide–arsenide (Fe, S, As, Pb, Mo, Ni and Co, in most cases) and carbonate (Ca and Mg) affinities in both areas. However, there was an important phosphate and zircon association in the Chongqing coal, whereas the carbonate association was significantly influenced by magma in the coals from Hubei. In the Late Triassic coal most of the major and trace elements investigated occur in aluminosilicate associations, with the exception of S, Fe, Ca, Mn, Sr, Sn, Ba, Nb, Mo, Mg, Co and Ta, with carbonate, sulphate and sulphide affinities. [Copyright &y& Elsevier]

Abstract: The occurrence and distribution of minerals, and major and trace elements of the coal #6-1 from the Cretaceous Wulantuga high-germanium coal deposit in Shengli coal field, Inner Mongolia are investigated. The major mineral constituents of coal #6-1 are quartz (15%), kaolinite (4–5%), illite (1%), pyrite (<1%), feldspars (<1%), gypsum (weathering product, <2%) and traces of chlorite. In addition to these phases, traces of scheelite (CaWO4) and weddellite (an oxalate, CaC2O4·2H2O) were also detected by XRD. On the basis of chemical and mineralogical properties, a clear differentiation was found between the upper and lower coal sections: the lower section with higher sulfide mineral content, and the upper one with low sulfur content and with a higher proportion of mineral phases formed/accumulated under oxidizing conditions (quartz and dolomite). This coal seam is highly enriched in Ge, As, W, and Hg (one to two orders of magnitude higher than the usual worldwide coal concentrations), with high contents of Sb, U, Cs, and Be (one order of magnitude higher than the usual worldwide coal concentrations). The geochemical and mineralogical profile patterns of the coal seam were attributed to the development of a basal reduced marsh environment evolving towards a more oxidizing marsh environment in the upper part of the coal seam. This could be related to the evolution from a high water table low moor marsh environment to a high moor marsh into an open water body with a higher detrital influence at the top of the seam. These syngenetic geochemical characteristics are possibly modified by an unusually intensive hydrothermal alteration causing the formation of oxalate minerals and the enrichment in a series of elements such as Cs, Be, U, As, Se, and Hg. [Copyright &y& Elsevier]

Abstract: A detailed study of the coalification and paleogeothermal evolution of the Stephanian Cevennes basin in southeastern France is presented in this paper. This study includes several parameters: 1) the geometry of the basement, the base of the coal measures and the unconformity beneath the overlying Mesozoic series, 2) the lateral and vertical distribution of the content of volatile matter in the coal beds, 3) the relationship between these parameters and the geological boundaries. This study also addresses qualitative and semi-quantitative parameters of the degree of coalification of organic matter in the same basin. The parameters investigated are: 1) the relief of the basement, 2) the nature and thickness of the overlying Mesozoic series, and 3) the faulting in the basin. In the Cevennes basin two coalification episodes were recognized (early pre-folding and late post-folding), and their ages and intensities have been estimated. The results suggest that coalification was strongly influenced by the faulting and the thickness of the strata overlying the coal seams. The early coalification episode during the Pennsylvanian basin-filling stage was closely related to the syndepositional faulting, and the later coalification episode was affected by subsequent rapid subsidence during the Mesozoic. The ultimate maturity level of the oldest Stephanian coal was achieved by the polyphase and multiformity coalification. [Copyright &y& Elsevier]

Abstract: The concentration of trace elements and their distribution in the late Permian coal in the Heshan coal field, Guangxi Autonomous Region, were analysed in this paper. The late Permian coal of the Heshan mining district was developed in a low energy and shallow, confined carbonate platform. Heshan coal is a low volatile bituminous coal characterized by a high sulphur content, ranging between 2.0% and 8.2%. Compared with the worldwide average content of the trace elements in coal, the content of some trace element in the study coal is markedly high (Bi, Ce, Cr, Cs, Cu, Ga, Hf, Sr, Ta, Th, U, V, W, Y, Zr, La, Mo, Nb and Sc). The trace element associations were investigated by means of intracorrelation analysis. Some elements, such as Cl, F and Sr are found in coal in association with the carbonate minerals. V, Cr, Zn, Mo, Ni and As contents in coal vary significantly amongst the coal samples. They are mainly concentrated in the lower part of the coal #4 upper of Suhe and Lilan mines and the coal #4 lower of Dong mine, and these possibly occurring in minerals such as arsenide and sulphide. The content of U in Heshan coal is high and is mainly concentrated at the upper and the lower parts of the coal seam and it is associated with mineral assemblages with Ba, Mo, V, Ni, Zn, Rb and Cr. Furthermore, La and Ce are highly correlated with those found in phosphate minerals and Pb, Sc, Ga, Th, Y and Sn to those in aluminosilicate minerals. The enrichment of some elements such as V, Cr, Zn, Mo, Ni, Rb as well as total sulphur and iron in the lower part of most coal seams might be associated with the formation of soil horizon before the accumulation of peat in the basin. Some other elements such as Cl, F, Sr and Ca are locally concentrated in the top of specific coal seams as a result of the leaching from overlying carbonates. [Copyright &y& Elsevier]

The occurrence and distribution of major and trace elements have been investigated in two coal-bearing units in the Chonqing mining district (South China): the Late Permian and Late Triassic coals.The Late Permian coals have higher S contents than the Late Triassic coals due to the fixation of pyrite in marine-influenced coal-forming environments. The occurrence of pyrite accounts for the association of a large number of elements (Fe, S, As, Cd, Co, Cu, Mn, Mo, Ni, Pb, Sb, Se, and Zn) with sulphides, as deduced from the analysis of the density fractions. The marine influence is probably also responsible for the organic association of B. The REEs, Zr, Nb, and Hf, are enriched by a factor of 2–3 with respect to the highest levels fixed for the usual worldwide concentration ranges in coal for these elements. The content of these elements in the Late Permian coal is higher by a factor of 5–10 with respect to the Late Triassic coal. Furthermore, other elements, such as Cu, P, Th, U, V, and Y, are relatively enriched with respect to the common range values, with maximum values higher than the usual range or close to the maximum levels in coal. The content of these elements in the Late Permian coal is higher than the Late Triassic coal. These geochemical enrichments are the consequence of the occurrence, in relatively high levels, of phosphate minerals, such as apatite, xenotime, and monazite, as deduced from the study of the density fractions obtained from the bulk coal.The Late Triassic coal has a low sulphur content with a major organic affinity. The trace element contents are low when compared with worldwide ranges for coal. In this coal, the trace element distribution is governed by clay minerals, carbonate minerals, and to a lesser extent, by organic matter and sulphide minerals.Major differences found between late Permian and Triassic coals are probably related to the source rocks, given that the main source rock of the late Permian epicontinental marine basin is the Emeishan basalt formation, characterised by a high phosphate content. [Copyright &y& Elsevier]

The abnormal enrichment of the REY (rare earth elements and yttrium)-Zr (Hf)-Nb (Ta) assemblage in Late Permian coals occurring in some coalfields in SW China has been extensively investigated, but the geological controlling factors of this assemblage are still under debate. This study reports on the mineralogical and geochemical features of coals and noncoal rocks collected from the Yudai and Jinqi coal mines within the Qiandongbei Coalfield in Guizhou Province to elucidate the geological controls on the distribution of REY-Zr (Hf)-Nb (Ta) enrichment horizons. The studied coals show rather consistent clay mineral assemblage of kaolinite, together with varying amounts of quartz, gypsum, pyrite, and calcite. Notably, the coals are anomalously enriched in REY, Nb, Ta, Zr, and Hf and enriched in other incompatible elements (e.g., Ga, Th, and U). Phosphates (e.g., florencite) and, to a lesser extent, zircon are the primary carriers of REY. Zirconium and Hf are mainly incorporated into zircon and then anatase, the latter of which is a predominant carrier of Nb and Ta. The detrital materials originate from a mixture of the erupted felsic volcanic ash resembling a peralkaline rhyolite composition and the eroded materials of Emeishan Large Igneous Province (ELIP) basalts. The studied coals owe their highly enhanced concentrations of the REY-Zr (Hf)-Nb (Ta) assemblage to the input of felsic volcanic ash, wherein the highly acidic aqueous solutions allowed these elements to become mobile and be redistributed. Both geological processes governed the distribution of REY-Zr (Hf)-Nb (Ta) enrichment horizons. The highly acidic solutions were possibly derived from the oxidation of peat bogs and volcanism-related acidic rain. The concentrations of REY, Zr, and Nb in the coal ashes exceed their corresponding cut-off grades; thus, these coals can be considered highly promising raw material sources for the REY-Zr (Hf)-Nb (Ta) assemblage. • The studied coals are significantly enriched in REY-Zr (Hf)-Nb (Ta) assemblage. • Detrital materials are derived from a mixture of felsic volcanic ash and eroded mafic materials. • The joint influence of highly acidic solutions and volcanism governs the REY-Zr (Hf)-Nb (Ta) enrichment horizons. • The volcanic ash erupted into peat bogs is geochemically similar to the peralkaline rhyolite. [ABSTRACT FROM AUTHOR]

Previous investigations on major and trace elements within the Early Permian coals from Xinjiang Province are very scarce. This paper reports on the geochemistry of the Early Permian coals and associated non-coal rocks in the Jimunai depression, Xinjiang Province, northwestern China. Samples collected from coal exploration boreholes ZK2603, ZK3003, and ZKH1102 as well as the Haerjiao underground coal mine (Nos. HRJ-7 and HRJ-9 Coals) in the Jimunai Depression were analyzed using SEM-EDS, ICP-AES, and ICP-MS. These Early Permian coals reach the rank of semi-anthracite to anthracite and have low-sulfur contents (0.30% on average). In comparison with the average element concentrations of world coals, Zr, Hf, and rare earth elements and Y (REY) are slightly enriched (concentration coefficient (CC) = 2–5, as the ratio of element content in sample vs. that in world coals) and Mn is enriched (CC = 5–10) in the ZK2603, ZK3003, and ZKH1102 coals. Niobium and Ta are highly enriched in the ZK2603 and ZK3003 coals (CC = 10–100). The HRJ-7 and HRJ-9 coals are slightly enriched in Mn (CC = 2–5). The coals have a sediment source region mainly composed of intermediate-felsic compositions from the Saur Volcanic Arc to the south of the Jimunai Depression, which may have provided relatively high geochemical background concentrations of Zr, Hf, Nb, and Ta. Manganese is hosted mainly in ankerite that was derived from epigenetic precipitation from Mn-bearing hydrothermal fluids. Zirconium and Hf in the ZK2603, ZK3003, and ZKH1102 coals are controlled primarily by detrital matter or hydrothermal fluids, the latter of which results in the higher Zr/Hf ratio in the ZK2603 and ZK3003 coals due to the re-distribution of Zr and Hf. Niobium and Ta in the ZK2603 and ZK3003 coals are concentrated chiefly in zircon, and hydrothermal fluid activity caused the release of Nb and Ta from previously-existing inorganic constituents and subsequent incorporation into zircon, resulting in the lower Nb/Ta ratio due to Ta being more easily incorporated into zircon than Nb. REY are hosted primarily within multiple mineral phases (e.g., zircon, phosphates, anatase, clay minerals) and their enrichment results from a combination of detrital matter input and hydrothermal fluid influx, the former of which is evidenced by the occurrence of REY-bearing detrital zircon and anatase, and the latter of which is indicated by the existence of REY-bearing authigenic rhabdophane and anatase and corroded anatase particles, as well as by the positive Gd anomalies and MREY-type or HREY-type REY distribution patterns. • The elevated Zr, Hf, Nb, and Ta are hosted mainly in zircon. • Hydrothermal fluid causes redistribution of Zr, Hf, Nb, Ta, and REY. • The enhanced Mn concentration was derived from epigenetic hydrothermal solution. • Terrigenous material and hydrothermal activity contribute to geochemical anomaly. [ABSTRACT FROM AUTHOR]

Brittle minerals, especially quartz, play an important role in the quality of shale reservoir. The precipitation of authigenic quartz caused a significant change in the rock stiffness and porosity. However, the formation mechanism of authigenic quartz in shale is still unclear. Lower Cambrian Niutitang shale from Guchengcun outcrop has been examined with respect to quartz cement. Four different types of quartz have been identified using SEM/CL/EDS. Type 1 occurs as angular to sub-rounded silt-size quartz grains with uniform luminescence, indicative of detrital origin. Type 2 appears as relatively large quartz aggregates approximately 30–150 μm in size, which is composed of small quartz grains (1–3 μm) and abundant in siliceous shale. The petrological evidence and consideration of potential diagenetic process suggest that Type 2 quartz was formed by local re-crystallization of biogenic silica in syndiagenesis and preferentially precipitated in the axial cavities of sponge spicules. Type 3 occurs as quartz overgrowths that are essentially non-luminescent at the periphery of high luminescence detrital quartz grains. This type quartz is present in most investigated samples. Type 4 represents microcrystalline quartz embedded in the illitized clay matrix as discrete, short chains or small clusters/nests and they are most commonly observed in argillaceous shale. The petrological evidence and CL responses indicate that both Type 3 and Type 4 quartz are derived from precipitation of silica released during the smectite to illite dissolution–precipitation reaction. S-I transition can be driven by microbial metabolic processes in shallow buried diagenesis or by heat and pressure in late diagenesis. Some of Type 4 quartz may be originated from low-temperature microbial pathway in shallow buried diagenesis, while Type 3 quartz and the remaining Type 4 quartz were formed in late diagenesis. Siliceous shale contains less abundant detrital quartz than argillaceous shale, indicating that siliceous shale was deposited in deeper water and far from terrigenous input than argillaceous shale. Although identifying the exact cause for diagenetic silica deposition in shale is not a trivial matter, its recognition is important for the reconstruction of the depositional history of shale sequences and understanding the role of diagenesis in shale reservoirs development, moreover, it also has great potential for enhancing prediction of mechanical rock properties in shales. [ABSTRACT FROM AUTHOR]

[Display omitted] • The late Triassic coals from, Northeastern Vietnam were formed in limnic sedimentary environment. • Coals from the Coc Sau open-pit mine in Cam Pha Coalfield are promising economic source of critical elements (Rb and Cs). • High enriched Rb and Cs in the Coc Sau coals most likely occur in K-rich clay minerals, e.g., muscovite. • Rb and Cs enrichment are originated from terrigenous influx from felsic-intermediate sediment provenance. The current study investigates the mineralogical and geochemical characteristics of the Late Triassic coals from the Coc Sau open-pit mine, Cam Pha Coalfield (Quang Ninh Province, Northeastern Vietnam) using Powder X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), inductively coupled plasma atomic-emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). Coals from Coc Sau open-pit mine are characterized by medium ash yield (avg. 29.7%), low sulfur content (avg. 0.17%), and low moisture content (avg. 1.8%). The volatile matter content (avg. 8.4%) indicates a semianthracite rank. The crystalline phases identified in Coc Sau coals and host rocks (roof, floor, parting) are primarily quartz, kaolinite and muscovite, with small proportions of ankerite, clinochlore, anatase, calcite, and tobelite. Illite, pyrite, and siderite were occasionally detected in individual samples. In addition, several minerals below the XRD detection limit, such as barite, apatite, zircon, xenotime, and florencite were observed by SEM. The low sulfur concentrations, low Sr/Ba ratio and relatively high ash yield of these coals indicate a continental lake basin sedimentary environment with a relatively strong supply of terrigenous detritus. Quartz, kaolinite, and muscovite were most likely derived from the terrigenous source region surrounding the basin, and the other minerals are mainly of authigenic origin. Relative to worldwide coals, the Coc Sau coals and host rocks are highly enriched in Rb and Cs, which can be a potential source for Rb and Cs recovery during coal utilization and combustion. Rubidium and Cs enriched in the coals are positively correlated with Al and K, indicating that they most likely occur in potassium-rich clay minerals (e.g., muscovite), and originate from weathered felsic terrigenous detritus. [ABSTRACT FROM AUTHOR]

• Mathematical models for pore pressure and in situ stress prediction were proposed. • The stress regime varies from reverse to normal faulting with increasing depth. • Deep coals retain a high differential stress and are relatively hard. • The influence of thrusting on the in situ stress diminishes with increasing depth. The southern Junggar Basin hosts abundant coalbed methane (CBM) resources and is expected to be an important CBM production base in China. The pore pressure and in situ stress are key factors that influence the exploration and development of CBM; however, these factors are poorly understood in this area. Based on extended leak-off test data, mathematical models were established for pore pressure and in situ stress prediction using regression analysis. Subsequently, the correlations between the pore pressure, in situ stress, and permeability were analyzed, and the stress ratios were investigated. Finally, the forming mechanism of stress zonation in the study area was discussed. The results show that CBM reservoirs are generally underpressured and partly overpressured at depths greater than 800 m in the study area. The study area is characterized by notable stress zoning. The stress regime varies from reverse to strike-slip to normal faulting with increasing depth. Significantly positive correlations exist between the pore pressure, maximum principal stress, minimum principal stress, vertical stress, and principal stress difference. The minimum horizontal stress is approximately 70% of the vertical stress in the study area. A mud weight window, varying from the pore pressure to the most likely breakdown pressure, is suggested. At depths greater than 600 m, a relatively high principal stress difference is observed, which indicates that deep coals have a relatively high mechanical strength and their permeability can be enhanced by hydraulic fracturing. The depth-dependent stress zonation is mainly due to the influence of thrusting on the in situ stress, which diminishes with increasing depth. The compressional stress regime in the shallow area benefits the sealing of faults and the preservation of CBM resources in the study area. The deep CBM resources have a development potential. The outcomes of this study contribute to the CBM exploration and development in the study area. [ABSTRACT FROM AUTHOR]

This study is the first to provide geochemical and paleoenvironmental information of Jurassic Xishanyao Formation coal in the eastern Junggar Basin, China. Twenty-seven coal core samples were collected from the zk0413 boreholes in Dajing area to determine the geochemical variability. Proximate analyses show that the Xishanyao Formation coal has the medium moisture content (average 13%), special low ash yield (average 6%) and high volatile matter (average 34%), which slightly fluctuate from bottom to top of coal seam. Organic matter in the coal are type III kerogen, with coalification degrees determined as subbituminous A or high volatile bituminous C. All coal samples have poor hydrocarbon generating potential with the yield between 31.93 and 72.36 (average of 43.57) mg HC/g.rock. The primary input of organic matter for coal-formation was higher terrestrial plants, with greater input from algae and micro-organisms and greater role of bacteria in plant degradation higher in the seam. The process of peatification in the lower section of the seam occurred under more acidic and oxic conditions. Coal accumulated in a lacustrine freshwater environment with the rise of the (ground) water table from bottom to top. There is evidence of higher salinity of water within the lower seam and decreased salinity (brackish to fresh water) within the middle of the seam, then an increase to moderate salinity (fresh water to brackish). The increasing stratified water column upward with reduced oxidation in the coal seams may result from the increased temperature in periods of a relatively hot and dry climate. The environment changes demonstrated in this study illustrate the importance of studying combined elemental and organic geochemistry to reconstruct paleoenvironment. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Upper Triassic coal from the Nui Hong open-pit mine is high-organic-sulfur coal. • The Nui Hong coal is promising economic source for strategic metal recovery. • Highly elevated Cs in coal most likely occurs in K-rich tobelite and illite. • Elevated Mo, Sb, U, Ge, and Tl are mainly associated with organic matter in coal. • Enrichment of strategic metals in Nui Hong coal is due to hydrothermal activities. Research on coal-hosted strategic metal ore deposits is an important subject in coal geology and mineral deposit worldwide. However, the related geological characteristics of coals from Vietnam have seldom been investigated, let alone the strategic metals in coals. This paper investigates the mineralogical and geochemical characteristics of the Upper Triassic coal from the Nui Hong open-pit mine, Thai Nguyen Coalfield, NE Vietnam, with emphasis on the enrichment of strategic metals in coal. The Nui Hong coal is low-volatile bituminous with high sulfur organic content. Minerals in the Nui Hong coal is predominantly composed of authigenic quartz, tobelite, pyrite, and calcite, with a small proportion of sphalerite, gypsum and fluorapatite in some coal bench samples. Mo-U-V-Se and Ge-W-Sb-Cs-Tl(-U) strategic metal element assemblages along with As-P toxic element association is significantly enriched in the Nui Hong coal, pointing to a significant economic benefit for Cs, Mo, U, and Ge recovery from the Nui Hong coal. The Ge enrichment in the Nui Hong coal provides a new perspective on prospecting of coal-hosted Ge deposit in high-rank coal. Cesium mostly occurs in K-rich aluminosilicate minerals (tobelite and/or illite), while Mo, Sb, U, Ge, and Tl are predominantly associated with organic matter in the Nui Hong coal. Multistage hydrothermal activities occurring in the marine-influenced S-rich, Fe-poor and clastic-starved anoxic-euxinic coal-forming environment are responsible for the significant enrichment of strategic metal elements in the upper Triassic coals from the Nui Hong open-pit mine, Thai Nguyen Province. [ABSTRACT FROM AUTHOR]

The paper investigates lateral variation of gas saturation and its geological controls of the No.2 coal seam in the Permian Shanxi Formation based on coal samples from 21 exploration wells in the Yanchuannan Coalbed Methane (CBM) Field, Southeastern Ordos Basin, China. The data set reveals that gas saturation of the No.2 coal seam shows a high lateral variation from 32.44% to 89.69%, and that there is an overall trend in gas saturation with depth overprinted by four other factors: 1) influence of faults, 2) secondary biogenic gas generation, 3) local top seal conditions and 4) variations in coal properties. The reverse faults F1 and F2 are effective barriers horizontally for the hydraulic communication and divide our study area into relatively closed and recharge zones. Gas saturation of the relatively closed zone is generally higher than that in the recharge zone. In the recharge, gas saturation increases generally along the flow pathway of groundwater with the exceptions of the areas affected by secondary biogenic gas. The stable isotope compositions suggest that late-stage biogenic methane was generated via CO 2 reduction associated with meteoric water recharge, which significantly contributes to higher gas saturation than expected. Meanwhile, the biogenic gas generation was/is restricted to shallow depths. The apparent variations in local areas of lithology of the overlying stratum next to the coal seam suggest that the top seal conditions are deteriorative, which can cause gas dissipation and reduce gas saturation remarkably. Integrally, for the variations in coal properties, gas saturation has a general positive relationship with coalification, and weak negative correlations with moisture content and ash yield but the relationships lacks statistical significances. Gas saturation is not associated with coal maceral in the study area. [ABSTRACT FROM AUTHOR]

This paper represents the first integrated research on the mineralogical, geochemical and stable isotope characteristics of the Upper Triassic high‑sulfur coals from the Khanh Hoa open-pit mine, Thai Nguyen Coalfield, NE Vietnam. Formed in a marine-influenced carbonate succession, the Khanh Hoa coal is characterized by medium ash yield, low volatile matter yield, and high sulfur content. Minerals in the Khanh Hoa coal are predominantly composed of authigenic calcite in the upper portion; and pyrite, quartz, with minor amounts of tobelite ([(NH 4), K] (Si, Al) 4 Al 2 O 10 (OH) 2), gypsum in the middle and lower portions. The high‑sulfur Khanh Hoa coal is enriched in an As-Mo-Sb-U-Cs-P assemblage, which presents both an organic and inorganic mode of occurrence, and is largely ascribed to hydrothermal fluids. The δ 13C values of the Khanh Hoa coal range from −24.77‰ to −22.80‰ (avg. −23.33‰), reflecting a change in sedimentation pattern (from transgressive to high stand system upwards). The δ 15N values of the Khanh Hoa coal range from 2.41‰ to 3.73‰ (avg. 3.30‰), possibly resulted from influenced by seawater influence and a redox environment. The mineralogical, geochemical and isotopic characteristics reflected that the high‑sulfur Khanh Hoa coal was formed/preserved in marine-influenced anoxic environment, with low detrital input, and strong activities of multi-stage hydrothermal solutions. [ABSTRACT FROM AUTHOR]

Antimicrobial resistance mediated by plasmid-borne AmpC β-lactamase in Gram-negative bacteria is an emerging event of significant clinical importance. Rapid and reliable detection of ampC is in urgent need for appropriate infection control. We described the development and evaluation of a heptaplex PCR melting curve analysis that could identify six groups of ampC , i.e., CIT, EBC, DHA, ACC, MOX and FOX, through predefined melting temperatures. The entire analysis could be finished within 2 h for 96 samples after template DNA was prepared. We first evaluated the assay with 176 AmpC-producing isolates of Escherichia coli and Klebsiella pneumoniae , and the results showed that 36 isolates were positive for ampC , including 18 positive for DHA, 12 for CIT, 5 for EBC, and one for both DHA and EBC. These results were fully concordant with sequencing analysis whereas the comparison method, an electrophoresis-based singleplex PCR assay, missed four isolates. The assay was also used to analyze 429 randomly selected clinically relevant Gram-negative isolates involving 22 different species, and 34 isolates were found to be ampC -positive. The results again fully agreed with the sequencing analysis. We conclude that the established assay could be used for rapid and reliable detection of ampC . [ABSTRACT FROM AUTHOR]

Underground coal mining produces large amounts of mine water annually in the Shendong mining area of China. Due to the severe scarcity of water resources, mine water is extensively used for productive, domestic, and ecological demands. However, mine water exhibits high fluoride levels. For water-use security, reduction of fluoride exposure and environmental protection, knowledge of sources and geochemical controls of fluoride enrichment in mine water is required. The results showed that F− concentrations of mine waters vary from 0.05 to 11.65 mg/L, with a mean value of 1.96 mg/L, and 51% of the mine waters contain F− concentrations exceeding the Chinese drinking water standard (1 mg/L). The overall mine water quality is influenced by cation exchange, mineral dissolution, pyrite oxidation, silicate weathering and so on. The high-fluoride mine waters are all associated with Na–type, with a remarkable cation composition feature of higher Na+ and lower Ca2+ and Mg2+ concentrations. Overall, the high-fluoride mine waters are well-matched with the water environment with higher pH, TDS, and EC levels. PCA reveals that the geochemical controls on the enrichment of F− in mine waters include dissolution of fluoride-bearing minerals and F−-OH− ion exchange; the former process is mainly caused by the decrease in Ca2+ concentrations resulting from Na + -Ca2+ cation exchange and mineral precipitation, and the latter process benefits from a highly alkaline water environment, facilitating the substitution of OH− in the mine water for F− within or absorbed on the minerals. Evaporation also controls F− enrichment in local areas. [Display omitted] • 51% of mine water samples exceed the Chinese drinking water limit for fluoride (1 mg/L). • The overall mine water quality is influenced by cation exchange, dissolution of minerals and so on. • NaHCO 3 type mine water possesses the highest average fluoride concentration. • Fluoride concentrations are overall proportional to higher pH, TDS, and EC levels. • Fluoride enrichment is related to ion exchange, mineral precipitation, and evaporation. [ABSTRACT FROM AUTHOR]

• Inorganic trace pollutants are studied in a coal-fired power station in China. • The aqueous (NH 4) 2 SO 4 slurry (pH 3.2) is enriched in inorganic trace pollutants. • NH 3 -FGD performance for the retention efficiency of trace pollutants is questioned. • Acidic conditions of the aqueous (NH 4) 2 SO 4 slurry could lead to low FGD efficiencies. • Operating conditions may affect Hg fate across the PCC-SCR-ESP-NH 3 -FGD. The behaviour and speciation of inorganic trace pollutants were studied in a 270 MWh coal-fired power station equipped with denitrification (DeNOx)-based selective catalytic reduction (SCR), electrostatic precipitators (ESP) and ammonia flue gas desulphurisation (NH 3 -FGD) controls. The aqueous (NH 4) 2 SO 4 slurry (pH 3.2) showed remarkably high concentrations of SO 4 2−, Cl−, Fe, NH 4 +, PO 4 3−, and F− and was substantially enriched in multiple trace pollutants, e.g. Mn, Ni, Zn, and As, which can be ascribed to the diffusion of gaseous pollutants released during combustion and to the partial dissolution of fly ash (FA) particles entrained in the flue gas FGD. These processes were favoured by the iteration of the FGD water re-circulation cycles within the scrubber. Three major unresolved performance issues remain for the NH 3 -FGD with respect to the retention efficiency of major and trace pollutants: (i) the high concentration of soluble salts and major and minor trace elements in the aqueous (NH 4) 2 SO 4 slurry could lead to entrainment of droplets and particles with the outgoing (OUT)-FGD gas; (ii) the ionic strength, as a result of the high concentration of the elements associated with soluble salts and major and minor elements, could lead to diminishing diffusivity of gaseous pollutants into the aqueous phase, where these are supposed to dissolve; and (iii) the acidic conditions of the aqueous (NH 4) 2 SO 4 slurry, caused by Fe-hydrolysis, could lead to low FGD efficiencies. Operating conditions at this power station affect Hg partitioning and fate across the PCC-SCR-ESP-NH 3- FGD. [ABSTRACT FROM AUTHOR]

Coal mining in China is continually increasing, and the associated emitted coal mine dust is of growing environmental and occupational concern. In this study, deposited coal mine dust (DD) was analysed in three different regions of an active, highly-volatile bituminous open-pit coal mine in the Xingjian Province, Northwest of China: coal working fronts, tailings handling sites, and road traffic sites. Samples were analysed for particle size, and geochemical and mineralogical patterns, and then compared with the respirable DD fractions (RDDs, <4 μm) separated from DD samples. Online measurements of ambient air concentrations of particulate matter (PM 10 and PM 2.5), black carbon (BC) and ultrafine particles (UFP) were performed in the same mine zones where DD was sampled. Furthermore, the RDD samples were subjected to analysis of specific biological response or toxicological indicators (oxidative potential, OP). The results demonstrated: i) large differences in particle size and composition among DD from tailings handling, road traffic and coal working front sites, ii) a strong influence of the DD moisture contents and ash yields on particle size, and, accordingly, on the potential dust emissions, iii) an enrichment of multiple elements (such as Nb, Th, Cr, Sr, Li, As, Pb, Cu, Zr and Ni) in the RDD from coal working fronts compared with their contents in the worked parent coal seams, mostly attributed to mining machinery, tyre and brake wear emissions and to deposition of dust emitted from gangue working zones, iv) low OP values of the RDD emitted from the studied mine, which works a high-quality coal, with OP being influenced by Mn, sulphate and anatase (TiO 2) contents, and v) the impact of specific mining operations and mine areas on the levels of air pollutants, such as high PM from tailings handling in the upper parts of the mine or the high UFP levels in the bottom of the mine (due to vehicle and machinery emissions and lower dispersive conditions). The data presented here demonstrate the necessity of extracting the more deeply respirable size fraction of coal mine dusts in future studies on the health effects of these materials because this finer fraction is mineralogically and geochemically different from the parent rocks. • High impact of specific mining operations in ambient air pollutants. • Particle size distribution of deposited dust (DD) was different over mine sites. • Moisture and ash have strong influence on respirable DD (RDD) emissions. • Enrichment of multiple elements in RDD attributed to mining activities. • Oxidative potential of RDD is influenced by Mn, sulphate and anatase contents. [ABSTRACT FROM AUTHOR]

• Respirable fraction of dust deposited inside coal mines was extracted and analysed • Respirable coal dust is enriched in minerals related to parent coal geochemistry • Deposited coal mine dust can be used as a proxy for the geochemistry of PM10 • Fe, Si, Mn, Ba and particle size of coal dust are highly correlated with toxicity We focus on a comparison of the geochemistry and mineralogy patterns found in coal, deposited dust (DD), respirable deposited dust (RDD) and inhalable suspended dust (PM10) from a number of underground mines located in China, with an emphasis on potential occupational health relevance. After obtaining the RDD from DD, a toxicological analysis (oxidative potential, OP) was carried out and compared with their geochemical patterns. The results demonstrate: i) a dependence of RDD/DD on the moisture content for high rank coals that does not exist for low rank coals; ii) RDD enrichment in a number of minerals and/or elements related to the parent coal, the wear on mining machinery, lime gunited walls and acid mine drainage; and iii) the geochemical patterns of RDD obtained from DD can be compared with PM10 with relatively good agreement, demonstrating that the characterization of DD and RDD can be used as a proxy to help evaluate the geochemical patterns of suspended PM10. With regards to the toxicological properties of RDD, the Fe content and other by-products of pyrite oxidation, as well as that of anatase, along with Si, Mn and Ba, and particle size (among others), were highly correlated with Ascorbic Acid and/or Glutathione OP. [ABSTRACT FROM AUTHOR]

Co-accumulation of carbon dioxide and hydrocarbon gas is common and widely existing in oil and gas basins. Such two natural pools are located in Lishui sag (East China Sea Shelf Basin), as a favorable prospecting area for exploration. CO 2 gas derived from inorganic mantle sources and CO 2 accumulation times have been investigated. In this study, petrographic observation shows pure CH 4 , CH 4 -rich, H 2 O-rich and hybrid CH 4 -CO 2 fluid inclusions exist in healed micro-fractures and overgrowths of quartz mineral in Palaeocene reservoirs of Lishui sag. The pressure–temperature–time–composition (PVT – x) properties of CH 4 -bearing inclusions were obtained by Raman quantitative analysis and thermodynamic models. These results provide important constraints on the P-T entrapment conditions and predict relative accumulation time of CH 4 fluid. Combination of carbon isotope analyses, inclusion petrography, microthermometry, PT entrapment conditions of CH 4 -bearing inclusions, hydrocarbon generation and simulation of burial history permit to assign periods of CH 4 fluid activity and its sequence with CO 2 fluid. Methane charging time occurs during two stages in LS-A: low density CH 4 fluid (~0.10 g/cm3 or lower) were trapped during late Oligocene (30-20 Ma) and high density (>0.115 g/cm3) during a Pliocene (8-1 Ma) CH 4 accumulation event. CO 2 fluid accumulation (Miocene, 21-4 Ma) displaced the methane gas trapped in the early stage. Pliocene CH 4 fluid partial displaced Miocene CO 2 fluid. In well B, only high density (0.144–0.153 g/cm3) recorded a late Oligocene to early Miocene (36-19 Ma) CH 4 accumulation event, Pliocene (5-3 Ma) CO 2 fluid displaced early CH 4 fluid. Micro-thermometry, composition of fluid inclusion, features of reservoir, thermal maturity reflect hydrothermal fluid vertical migration and the existence of Supercritical CO 2 extraction. • Hydrocarbon stable isotope show crude oil associated gas generation. • Petrography, micro-thermometry and Raman method discriminate the type of inclusion. • PVT-x properties of CH 4 -bearing inclusions were determined by Raman quantification. • Analysis of CH 4 accumulation time and displacement relationship with CO 2 fluid. [ABSTRACT FROM AUTHOR]