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Abstract: Batch leaching tests have been performed on fly ashes collected from four Australian power stations fuelled by chemically different coals. Two acidic and two alkaline fly ashes were subjected to long-term (144h) leaching tests, and the behaviour of As, B, Mo and Se was investigated to obtain data on their potential for mobilisation during fly ash–water interactions. All four elements are mobile under different conditions and over different leaching times. The concentrations of these elements released in leaching solutions with initial pH values of 4, 7 and 10 were used to assess the influence of pH conditions on element mobility from the acidic and alkaline fly ashes. The most mobile of the four elements leached were Mo from alkaline fly ashes and B from acidic fly ashes. Arsenic concentration increased with time in leachate solutions from acidic and alkaline fly ashes; however, in solutions in contact with alkaline fly ashes the As concentration, after reaching a maximum, later decreased with time. Selenium mobility shows a similar pattern to that of As, with similar leaching concentrations. Boron has the highest relative mobility of all four elements. A process possibly responsible for the decrease in concentration of B, As and Se in alkaline leaching solutions is the formation of ettringite. Equilibrium between the solid phase (ash) and the leaching solution was not reached in any of the leaching experiments. The pH of the leaching solution is the key factor affecting the mobility of these trace elements in these fly ashes. [Copyright &y& Elsevier]

Abstract Minerals and elements in coal are derived from the processes associated with peat accumulation and rank advance, as well as possibly a range of epigenetic processes, and thus can provide information on the depositional conditions and geologic history of coal beds and coal-bearing sequences, as well as perhaps on regional tectonics. This paper investigates the petrology, mineralogy, and geochemistry of anthracites and their host rocks (partings, roof, and floor strata) from two coal deposits (Hongmao and Luocheng) in Guangxi Province, southern China. Samples collected from these deposits were analyzed using optical microscopy, scanning electron microscopy plus energy-dispersive X-ray spectrometry, low-temperature ashing, X-ray diffraction, X-ray fluorescence spectrometry, and quadrupole-based inductively coupled plasma mass spectrometry. The anthracites from the two deposits are medium- to high-sulfur coals. The rare earth elements in the Luocheng anthracites are characterized by distinct positive Eu anomalies and medium- and heavy-REE enrichment types. The minerals in the Hongmao anthracites are characterized by the occurrence of K-illite, paragonite, and ammonian illite, which, however, are absent in the Luocheng anthracites. The paragonite, ammonian illite, and chlorite resulted from the alteration of pre-existing kaolinite by hot solutions containing Na+, NH 4 +, and Fe2+ respectively. The partings in the Luocheng anthracite seams contain pyrophyllite that was formed by reactions between kaolinite and quartz during injection of high-temperature solutions. The mineralogical and geochemical characteristics of the anthracites in the two deposits indicate that the coals were subjected to high-temperature (>250 °C) solutions that also elevated the coal rank to anthracite grade. The assemblage of K-illite-paragonite-NH 4 -illite in the coals of the Hongmao deposit was formed under greater hydrothermal but less tectonic influence compared to the Luocheng deposit; by contrast, the pyrophyllite-illite-chlorite assemblage of the Luocheng deposit reflects a greater tectonic but lesser hydrothermal influence. Highlights • Rare earth elements in the anthracites have distinct positive Eu anomalies and medium- and heavy-REE enrichment types. • The minerals in the anthracites are characterized by the occurrence of K-illite, paragonite, and ammonian illite. • Paragonite and ammonian illite resulted from the alteration of kaolinite by hot solutions containing Na+ and NH 4 +. • Pyrophyllite in partings of coalbed formed by reactions between kaolinite and quartz during injection of high-T solutions. • The mineralogical and geochemical characteristics of the anthracites indicate the injection of high-T (>250 °C) solutions. [ABSTRACT FROM AUTHOR]

The origin and modes of occurrence of rare metals in coal (e.g., rare earth elements, U, Se, Re, Ge, Ga, and Nb) have attracted much attention in recent years because such investigations can provide fundamental information for assessment of their economic significance. This paper investigates the abundance, modes of occurrence, and origin of rare metals in three Lopingian coals (LL5-K3, CG3-K6, and CG1-K7 Coals) from the Yishan Coalfield, Guangxi Province, southern China. The coals of this coalfield are preserved within carbonate successions and are characterized by super-high-organic sulfur (SHOS) contents (mostly 6–9%) and an elemental assemblage enriched in U-Se-Mo-V-Re. Two different hydrothermal solutions were responsible for the geochemical anomalies in the Yishan coals. One was responsible for the U-Se-Mo-V-Re enrichment in the three coal seams while the other was a high-temperature solution responsible for the positive Eu anomalies and the elevated rank ( R o,ran = 2.05%) of the LL5-K3 coal. The U, Se, Mo, V, and Re in the CG3-K6 and CG1-K7 coals mainly have an organic association, but the same elements in the LL5-K3 coal have a mixed organic-inorganic affinity, attributed to high-temperature leaching in the early coalification stage. In addition to highly elevated concentrations of U-Se-Mo-V-Re, the average concentration of oxides of the rare earth elements and Y in the LL5-K3 coal (1387 ppm on average, ash basis) is higher than the cut-off grade for industrial deposits of these elements and thus the coals also have potential as raw materials for the recovery of rare earth elements. [ABSTRACT FROM AUTHOR]

This paper reports the geochemical and mineralogical compositions of the Late Permian No. 25 Coal (semi-anthracite) and its host rocks (roof and floor strata) from the Guxu (Gulin–Xuyong) Coalfield, Sichuan Province, China. The coal is characterized by medium-sulfur content (average 2.73%) and has an average ash yield of 20.95%. In contrast to other Late Permian coals from southwestern China that are enriched in Sc, V, Cr, Co, Ni, and Cu, the No. 25 coal does not contain an abundance of these transition elements but is rich in lithophile elements Be, Y, Nb, Zr, Hf, and U. The elevated concentrations of trace elements in the No. 25 Coal were probably derived from the felsic–intermediate rocks at the top of the Emeishan basalt sequence, rather than from the Emeishan mafic basalts. The floor strata of the No. 25 Coal can be divided into two sub-sections. The upper sub-section of the sequence immediately below the No. 25 Coal consists of material with a felsic–intermediate composition probably derived from terrigenous sources and the lower sub-section is composed of mafic tuff. The terrigenous mineral matter in the No. 25 coal appears to have the same sediment-source region as the upper sub-section of the floor strata, based on their similar geochemical compositions. The roof strata of the No. 25 Coal are more quartzose, and were probably derived from a different sediment-source region. The mineral matter in the coal is dominated by kaolinite and, to a lesser extent, calcite and pyrite; the roof and floor strata each have quite different mineralogy, with kaolinite dominant in the latter and illite, kaolinite and quartz in the former; pyrite contents are variable both in the coal and in the host rocks. The floor strata and the coal have been affected by hydrothermal solutions, leading to the enrichment of rare earth elements and yttrium (REY), Nb, Ta, Zr, Hf, and U. The REY in the coal and floor strata, as well as the Nb, Ta, Zr, Hf, and U in the floor strata, represent potentially economic rare metal resources. [ABSTRACT FROM AUTHOR]

Coal deposits have attracted much attention in recent years as promising alternative raw sources for rare earth elements and yttrium (REY), not only because the REY concentrations in many coals or coal ashes are equal to or higher than those found in conventional types of REY ores but also because of the world-wide demand for REY in recent years has been greater than supply. In addition to anomalies of enrichment or depletion of light-, medium-, and heavy-REY in coal deposits (normalized to Upper Continental Crust, Post-Archean Australian Shale, or North American Shale Composite), anomalies of redox-sensitive Ce and Eu, and, in some cases, of non-redox-sensitive La, Gd, and Y, could be used as geochemical indicators of the sediment-source region, sedimentary environment, tectonic evolution, and post-depositional history of coal deposits. Factors controlling REY anomalies in coal deposits include the geochemistry of terrigenous source rocks, ingress of hydrothermal fluids, influence of marine environments, percolating natural waters, volcanic ashes, and sedimentary environments of peat formation. Additionally, the smoothness of a normalized REY distribution pattern provides a simple but reliable basis for testing the quality of REY chemical analyses for coal and other sedimentary rocks. [ABSTRACT FROM AUTHOR]

Coal fires burning around the world over many years have been responsible for the loss of natural resources and also for negative environmental and human-health impacts. Study of self-burning coal wastes based on organic petrology, mineralogy and geochemistry allows the evaluation of factors responsible for the combustion process, and can also be used to assess the changes that are taking place in thermally affected materials. The main goal of this study is to characterize the materials from the Arroyo Galladas, Arroyo Mourin and Fabero coal waste piles, which resulted from coal mining in the El Bierzo Coalfield (NW Spain). Samples of coal, and of unburned and burned or burning coal waste material, were studied by optical microscopy and X-ray powder diffraction (XRD). The results demonstrate that some of the organic matter has preserved its characteristics, but other organic material shows signs of thermal alteration such as cracks, devolatilization vacuoles, dark reaction rims, plasticized edges, and increased or decreased vitrinite reflectance. The resistance of the unaltered organic matter to thermal effects is attributed to the coalification process previously undergone by these coals. The mineralogical composition of the samples indicates that newly formed minerals are present in the burned or burning material, including mullite, cristobalite, cordierite, hematite, jarosite, sanidine, anorthite, sulfur, pyrite, rozenite, coquimbite, tschermigite, boussingaultite and amorphous material. The formation of these minerals is attributed to combustion at maximum temperatures of at least 1100 °C in the Fabero coal waste pile and lower temperatures in the Arroyo Galladas coal waste pile, and to interaction of gases released by combustion with the solid particles, the waters and the atmosphere in and around the waste piles. [ABSTRACT FROM AUTHOR]

To better understand the formation mechanism of coal-hosted Ge ore deposits, this paper reports on the petrological, mineralogical, and geochemical compositions of the low-Ge coals in the Shengli Coalfield (Inner Mongolia, China), using optical microscopy, field emission-scanning electron microscopy, X-ray fluorescence, X-ray diffraction, and inductively coupled plasma mass spectrometry. The samples in the present study closely neighbor the previously-reported Wulantuga coal-hosted Ge ore deposit (both No. 6 Coal). In comparison with the Wulantuga Ge-rich coals, the low-Ge coals of the Shengli field display higher moisture (27.59% on average) and lower pyritic sulfur contents (0.53%). Both the low-Ge and Ge-rich coals are generally high in inertinite, and have varying but relatively low huminite contents. Preservation of fecal pellets as macrinite is notable in both the low-Ge and Ge-rich coals, and the position of the fecal pellets appears to be within tunnels or chambers within the wood. Quartz, kaolinite, pyrite, and gypsum are the major crystalline phases identified in most of the Ge-rich and low-Ge coals, but the low-Ge coals contain significantly less pyrite and are more abundant in non-mineral Ca and Mg. Ca-oxalate of authigenic origin is observed, generally occurring as cell-fillings in the low-Ge coals. Otherwise mineral-free organic matter in the low-Ge coals would be expected to have an inherent ash yield of around 6%, derived from the inorganic elements (mainly non-mineral Ca and Mg) that occur either in the organic matter or as dissolved ions in the pore water and form the sulfate species in low-temperature (oxygen-plasma) ash residues. The highly-elevated trace elements, including Be, Ge, As, Sb, W, Hg, and Tl, that occur in the Ge-rich coals of the Wulantuga deposit, are significantly depleted in the low-Ge coals. Lateral migration of Ge–W- and As–Hg–Sb–Tl-rich solutions through the original peat swamp for the Wulantuga Ge ore deposit has led to significant enrichment of Ge on the margin of the coal basin but decreasing Ge concentrations toward to the inner part of the basin. Such a migration direction is different to those in the previously-reported for the hydrothermal solutions in the Lincang (Yunnan of China) and Spetzugli (Russian Far East) Ge ore deposits, where the solutions migrated vertically from granite to peat along faults and led to a dome-shaped Ge distribution in the relevant coal seam. [ABSTRACT FROM AUTHOR]

The Lincang Neogene high-Ge coal deposit in Yunnan, southwestern China, is one of the major coal-hosted Ge deposits in the world. This study reports new data on the petrological, mineralogical, and geochemical compositions of 57 samples (including coal bench samples, roofs, floors, partings, and batholith granite) of three high-Ge coal seams (S3, Z2, and X1) from the Dazhai Mine, Lincang Ge ore deposit, and provides new insights into the origin and modes of occurrence of the minerals and elements present. The coals have huminite random reflectances in the 0.33–0.48% range. On a mineral-free basis, the coal samples are dominated by huminite-group macerals, all having more than 88.5% total huminite. Ulminite and attrinite generally dominate the huminite macerals. Structured inertinite is rare, with funginite being the most abundant inertinite form. The minerals in the coals are mainly composed of quartz, and, to a lesser extent, kaolinite, illite, and mica. A hydrous beryllium sulfate phase (BeSO 4 ·4H 2 O) is present in the low temperature ashes of several coal samples. Compared to average values for world low-rank coals, beryllium (up to 2000 μg/g and 343 μg/g on average), Ge (up to 2176 μg/g and 1590 μg/g on average), and W (up to 339 μg/g and 170 μg/g on average) are unusually enriched in the Lincang coals, with a concentration coefficient > 100 (CC = ratio of element concentration in investigated coals vs. world low-rank coals); elements As (156 μg/g on average), Sb (38 μg/g), Cs (25.2 μg/g), and U (52.5 μg/g) are significantly enriched (10 < CC < 100); niobium (28.2 μg/g) is enriched (CC = 8.55); zinc, Rb, Y, Cd, Sn, Er, Yb, Lu, Hg, Tl, and Pb are slightly enriched (2 < CC < 5). The biotite- and two-mica granites, which served as both the basement for the coal-bearing sequence and as a source of sediment input, were also either hydrothermally-altered or -argillized. The alteration appears to have taken place during or shortly after deposition of the coal-bearing sequence. Two types of metasomatites of hydrothermal origin, including quartz–carbonate and carbonate, were identified, which occur as partings and as roof and floor strata. These metasomatites were formed at the syngenetic or early diagenetic stages of coal deposition. The rare earth elements in these hydrothermal rocks are characterized by a heavy REE enrichment type and by distinct positive Eu anomalies, compared to the upper continental crust. Hydrothermal solutions have played a significant role in producing the elemental and mineralogical anomalies in the Lincang Ge ore deposit. The hydrothermal solutions leaching the batholith granite were a mixture of alkaline N 2 -bearing and volcanogenic CO 2 -bearing fluids, which led to the enrichment of trace elements, not only including assemblages of Ge–W and Be–Nb–U (both leached from granite and the deposited in the peat), but also As–Sb (from volcanogenic solution), as well as the alteration and argillization of the batholith granites, and the formation of carbonate and quartz–carbonate metasomatites. [ABSTRACT FROM AUTHOR]

This study has investigated the effect of small igneous intrusions on Early Cretaceous carbonaceous fluvial sediments of the Gippsland Basin of south-eastern Australia, based on outcrops in the onshore western part of the basin. Vitrinite reflectance measurements, quantitative mineral phases and clay mineralogy were carried out on twenty two samples of organic-rich mudstone up to 25 m east and west of a 1 m wide dyke. Samples of the dyke allowed classification as an alkali-basalt, based on its optical characteristics, and major- and trace-element properties. Background vitrinite reflectance of 0.75%–0.80% [R max ] in the sediments is elevated up to 6.67% [R max ] close to the dyke margin, with slightly different patterns on each side of the intrusion. Analysis of seven selected organic-rich mudstone samples shows that they all have very similar XRD patterns, with the main minerals in all cases being quartz, feldspar (mainly plagioclase), chlorite, illite and interstratified illite/smectite. These observations suggest that the thermal maturity of the organic matter in the sediments was locally elevated by heating due to emplacement of the dyke, but no significant changes were observed in host-rock mineralogy that could be related to the heat generated by the dyke and the associated vitrinite reflectance variations. [ABSTRACT FROM AUTHOR]

The petrological, geochemical, and mineralogical compositions of the coal-hosted Jurassic uranium ore deposit in the Yili Basin of Xinjiang province, northwestern China, were investigated using optical microscopy and field emission-scanning electron microscopy in conjunction with an energy-dispersive X-ray spectrometer, as well as X-ray powder diffraction, X-ray fluorescence, and inductively coupled plasma mass spectrometry. The Yili coal is of high volatile C/B bituminous rank (0.51–0.59% vitrinite reflectance) and has a medium sulfur content (1.32% on average). Fusinite and semifusinite generally dominate the maceral assemblage, which exhibits forms suggesting fire-driven formation of those macerals together with forms suggesting degradation of wood followed by burning. The Yili coals are characterized by high concentrations of U (up to 7207 μg/g), Se (up to 253 μg/g), Mo (1248 μg/g), and Re (up to 34 μg/g), as well as As (up to 234 μg/g) and Hg (up to 3858 ng/g). Relative to the upper continental crust, the rare earth elements (REEs) in the coals are characterized by heavy or/and medium REE enrichment. The minerals in the Yili coals are mainly quartz, kaolinite, illite and illite/smectite, as well as, to a lesser extent, K-feldspar, chlorite, pyrite, and trace amounts of calcite, dolomite, amphibole, millerite, chalcopyrite, cattierite, siegenite, ferroselite, krutaite, eskebornite, pitchblende, coffinite, silicorhabdophane, and zircon. The enrichment and modes of occurrence of the trace elements, and also of the minerals in the coal, are attributed to derivation from a sediment source region of felsic and intermediate petrological composition, and to two different later-stage solutions (a U–Se–Mo–Re rich infiltrational and a Hg–As-rich exfiltrational volcanogenic solution). The main elements with high enrichment factors, U, Se, As, and Hg, overall exhibit a mixed organic–inorganic affinity. The uranium minerals, pitchblende and coffinite, occur as cavity-fillings in structured inertinite macerals. Selenium, As, and Hg in high-pyrite samples mainly show a sulfide affinity. [ABSTRACT FROM AUTHOR]

The content, modes of occurrence, and origin of elements and phosphorus minerals in the Jurassic coals of the Muli Coalfield, on the Tibetan Plateau, were investigated using optical microscopy, field emission-scanning electron microscopy in conjunction with energy-dispersive X-ray spectrometry, X-ray powder diffraction, X-ray fluorescence spectrometry, and inductively coupled plasma mass spectrometry. The Muli coals (L1 and L2 Coals) are of high volatile A bituminous to medium volatile bituminous rank, characterized by low-sulfur contents, and are generally dominated by the inertinite-group macerals (predominantly semifusinite and fusinite). The L1 Coal contains abundant apatite (7.9% on average, on an organic-matter-free basis) and alumino-phosphate minerals of goyazite–gorceixite–crandallite group (4.9% on average), and, accordingly, the concentrations of elements F (253 μg/g on average), P (2349 μg/g), Sr (526 μg/g), and Ba (790 μg/g) are elevated as compared with common world hard coals. The deposition of phosphorous-bearing minerals in the Muli coals was not derived from volcanic input; penetration of Ca- and Al-rich solutions, release of phosphorus from organic matter during plant decay, and an appropriate sedimentary environment (such as low pH, low water table for peat, and oxidizing conditions) were critical factors in deposition of the phosphorus minerals. [ABSTRACT FROM AUTHOR]

The background and anthropogenic levels of hazardous elements in the surface soil of a coal mining area depend on the geological setting of the region and the underlying soil material, but may also be influenced by water-borne or aeolian transport of sediment from adjacent coal-related waste piles. Very few studies have focused on the chemical and mineralogical composition of Brazilian coal cleaning rejects (CCRs), which may represent significant sources of soil or water contamination. In this study, we have investigated the quantitative distribution of minerals and potentially hazardous elements in CCRs and a run-of-mine coal from the Brazilian states of Rio Grande do Sul and Santa Catarina. The major minerals, identified by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), and field-emission scanning electron microscopy/energy dispersive X-ray analysis techniques (FE-SEM/EDS) are kaolinite, quartz, mixed-layer illite-smectite, pyrite, jarosite, melanterite, gypsum, rutile, and calcite, while minor minerals include barite, hematite, siderite, sphalerite, and goethite. Galena, magnetite, zircon, and many other species may also occur as accessory/trace minerals. Pyrite and jarosite are relatively abundant in some cases, making up to around 4% or 5% of the mineral matter, with jarosite, melanterite, and gypsum probably formed by complex interaction of oxidation products from Fe-sulfides and clay or carbonate components, initiated by exposure and storage of the host material. Such atmospheric exposure promotes sulfide oxidation that releases substantial sulfate loads as well as Ca2+, K+, Mg2+, Cl-, and Al3+. Metals with the most severe discharges were Zn, Cu, Mn, Co, Ni, and Cd. Most of the trace pollutants in the CCRs displayed a pH-dependent solubility, being immobile in near-neutral samples but mobile under the low-pH conditions associated with oxidized material. The results highlight the complex interactions among mineral matter components of the CCRs during storage, and the potential for release of potentially hazardous elements in association with longer-term exposure and storage. [ABSTRACT FROM AUTHOR]

Abstract: The fly ashes derived from three giant coal-hosted Ge deposits, Lincang (Yunnan of southwestern China), Wulantuga (Inner Mongolia of northern China), and Spetzugli (Primorye, Russian Far East), are unique because they are highly enriched in elements, including up to (on an organic-free basis): 4.66% Ge, 2.12% As, 1.56% F, 1.22% Sb, 0.56% W, 0.56% Zn, 0.55% Pb, 0.13% Sn, 0.12% Ga, 0.056% Bi, 0.04% Be, 0.028% Cs, 0.017% Tl, and 0.016% Hg. These high element concentrations in the fly ashes are due both to their high levels in the raw coals from which they were derived and their high volatility during the coal combustion process. Rare earth elements and yttrium (REY) were fractionated during coal combustion. They are more enriched in fly ashes than in slag from the respective coals. Maximum REY enrichment may occur either in fine-grained fly ash from baghouse filters or in coarse-grained fly ash from electrostatic precipitators. Cerium and Eu are more enriched in the fly ashes than other REY, and yttrium is relatively depleted in the fly ashes in comparison with the slag. Three types of unburnt carbon can be identified in the fly ashes: (1) carbon with well-preserved initial maceral structures (fusinite and secretinite), (2) isotropic and anisotropic carbon, and (3) secondary fine-grained carbon. The last type of unburnt carbon is characterized by embedded fine-grained Ge-bearing and other mineral phases. Ge oxides (e.g., GeO2) are the major Ge carrier in the fly ashes. Other Ge-bearing mineral phases, however, were also identified, including glass, Ca ferrites, solid solutions of Ge in SiO2, and probably elemental Ge or Ge (Ge-W) carbide, as well as previously-unknown complex oxides including (Ge,As)Ox, (Ge,As,Sb)Ox, (Ge,As,W)Ox, and (Ge,W)Ox. Some portion of the Ge occurs as adsorbed species in different types of unburnt carbon (Types 1 and 2) in the ash particles. [Copyright &y& Elsevier]

Abstract: The Late Permian coal in the Fusui Coalfield of southern China is characterized by high Fe-sulfide and organic sulfur contents (2.60 and 2.94%, respectively). Trace elements including Zr (354μg/g on average), Hf (9.18μg/g), Y and rare earth elements (REY, 302μg/g), Li (97.9μg/g), and Cs (7.02μg/g) are significantly enriched in these coals. In addition to Hg and Se enrichment in the roof and floor of the coal, fluorine, Mo, and U are enriched in the roof; the floor is rich in Cl, S, Fe, Pb, and Cd. Compared to the upper continental crust, REY in the parting and coal bench samples are characterized by heavy-REY and light-REY enrichment, respectively; the coals, partings, and host rocks (roof and floor) have negative Eu anomalies. The coal benches have higher ratios of U/Th, Yb/La, Nb/Ta, and Zr/Hf, and more abundant heavy rare earth elements than their adjacent partings. These geochemical anomalies are attributed to the composition of terrigenous materials derived from the Yunkai Upland, multi-stage (syngenetic and epigenetic) hydrothermal fluid activities, and intensive leaching and re-distribution of lithophile elements from partings to the underlying coal benches. Both the organic and sulfide sulfur are also derived mainly from the hydrothermal fluids rather than the marine influence. The minerals in the samples studied, including kaolinite, quartz, and REE-bearing minerals, are of both terrigenous and hydrothermal origin. Al-oxyhydroxides, crystalline FeSO4(OH), water-bearing Fe-oxysulfate, and goyazite were derived from the hydrothermal activity. Kaolinite, quartz, REE-bearing minerals, and apatite from the sediment source region were also subjected to destruction by hydrothermal fluid leaching. [Copyright &y& Elsevier]

Abstract: Aluminum-hydroxide (boehmite and diaspore)-, Ga-, REY (rare earth elements and Y)-, and Al-rich Pennsylvanian Taiyuan Formation coals have previously been found in the Jungar and Daqingshan Coalfields, Inner Mongolia, China. Gallium, REY, and Al are potentially extractable and usable elements in combustion residues derived from these coals. This paper reports new results on 50 bench samples of the No. 6 coal from the Guanbanwusu Mine, Jungar Coalfield, Inner Mongolia, and provides new data and evidence for the existence of an Al (Ga, REY) ore deposit in the unique Jungar Coalfield. The No. 6 coal in the Guanbanwusu Mine has a low rank (Ro,ran =0.56%) and a low-sulfur content (St,d =0.58%). The proportion of inertinite in the coal (56.7%; mineral-free basis) is higher than that of vitrinite (31%). The minerals in the coal are mainly represented by kaolinite, boehmite, and chlorite, along with variable proportions in some samples of calcite, ankerite, siderite, and goyazite. Boehmite, goyazite, and part of the kaolinite were derived from bauxite in the weathered surface of the sediment-source region. Ankerite, calcite, and siderite in the coal are of authigenic origin. The chlorite in the Guanbanwusu coals appears to have a chemical composition intermediate between cookeite and chamosite. This mineral mainly occurs as cell-fillings, also indicating an authigenic origin, and was probably derived from hydrothermal fluids. A new mineral phase mainly composed of Ti, Cl, and Fe is probably a Ti-bearing oxychloride or hydroxychloride. Compared to other Chinese coals and to world hard coals, the coal from the Guanbanwusu Mine is enriched in Al2O3 (9.34%), P2O5 (0.126%), Li (175μg/g), F (434μg/g), Cl (1542μg/g), Ga (12.9μg/g), Sr (703μg/g), and Th (12.9μg/g), but has a lower SiO2/Al2O3 ratio (0.74) due to the higher proportions of boehmite and goyazite in the coal. The major carrier of P2O5 and Sr is goyazite. Lithium mainly occurs in the chlorite (cf. cookeite), kaolinite, and possibly, to a lesser extent, illite. Fluorine in the coal has a major boehmite affinity, but a small proportion may also occur in the organic matter and chlorite. Gallium in the coal largely occurs in goyazite. Chlorine is independent of other elements in the coal, associated neither with moisture nor with organic matter, but possibly occurring in molecular form (Cl2) and in the Ti-bearing oxychloride or hydroxychloride. Thorium in the coal occurs in the clay and accessory minerals, and was mainly derived from detrital materials of the source region. Rare earth elements and Y have a mixed (organic and inorganic) affinity, largely occurring in goyazite-group minerals and, to a lesser extent, boehmite and organic matter. Most coal benches and partings have either an L-type or H-type of REY enrichment, owing respectively to the weathered bauxite source region and groundwater effects. The Al2O3, Ga, REY and possibly Li in the Guanbanwusu coals, like those in coals from the Jungar and adjacent Daqingshan Coalfields, are industrially useful metals that could potentially be recovered from the relevant coal combustion residues. It is suggested that, if Ga in ash>50μg/g, REY>800–900μg/g, SiO2/Al2O3 <1 (or Al2O3 >40% in ash), and coal thickness>5m, the coal combustion residues would be expected to be suitably enriched in Al2O3 and can be considered for Al2O3, Ga, and REY recovery. [Copyright &y& Elsevier]

Abstract Coal combustion and the disposal of combustion wastes emit enormous quantities of nano-sized particles that pose significant health concerns on exposure, particularly in unindustrialized countries. Samples of fresh and weathered class F fly ash were analysed through various techniques including X-ray fluorescence (XRF), X-ray diffraction (XRD), focused ion beam scanning electron microscopy (FIB-SEM), field-emission gun scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM) coupled with energy dispersive x-ray spectroscopy (EDS), and Raman Spectroscopy. The imaging techniques showed that the fresh and weathered coal fly ash nanoparticles (CFA-NPs) are mostly spherical shaped. The crystalline phases detected were quartz, mullite, ettringite, calcite, maghemite, hematite, gypsum, magnetite, clay residues, and sulphides. The most abundant crystalline phases were quartz mixed with Al-Fe-Si-K-Ti-O-amorphous phases whereas mullite was detected in several amorphous phases of Al, Fe, Ca, Si, O, K, Mg, Mn, and P. The analyses revealed that CFA-NPs are 5–500 nm in diameter and encapsulate several potentially hazardous elements (PHEs). The carbon species were detected as 5–50 nm carbon nanoballs of graphitic layers and massive fullerenes. Lastly, the aspects of health risks related to exposure to some detected ambient nanoparticles are also discussed. Graphical abstract Unlabelled Image Highlights • The CFAs nanoparticles are 5-500 nm in diameter and contain several potential hazardous elements (PHEs). • Carbon species such as graphitic layers and massive fullerenes are present in the fresh and unsaturated weathered CFAs • Quartz is mixed with Al-Fe-Si-K-Ti-O amorphous phases but mullite is linked with Al, Fe, Ca, Si, O, K, Mg, Mn, and P amorphous phases. [ABSTRACT FROM AUTHOR]

This paper discusses the identification, abundance, modes of occurrence and origin of buddingtonite and associated minerals in three Lopingian coals from the Yishan Coalfield, Guangxi Province, southern China. The coals of this coalfield are preserved within carbonate successions and are characterized by super-high-organic sulphur contents (mostly 6–9%). Three different types of feldspars have been identified in these coals, buddingtonite, albite and minor K-feldspar. Both the albite and K-feldspar in the coal were largely derived from detrital materials of terrigenous origin, although some were authigenically deposited; they were subsequently subjected to corrosion/dissolution by percolating fluids. Buddingtonite was derived largely from K-feldspar via diffusion mechanisms through the substitution of K + by NH 4 + , the latter coming from decomposition of organic matter in the coal, or from changes in the organic matter with rank advance. A small proportion of the buddingtonite was also derived from albite through the replacement of Na + by NH 4 + . [ABSTRACT FROM AUTHOR]

Previous investigations on minerals and elements in coals from northeastern China are very scarce. This paper investigates the mineralogy and geochemistry of the Palaeogene No. 19-2 Coal, parting, and host rocks (roof and floor strata) in the Baliancheng mine, Hunchun Coalfield, Jilin Province, northeastern China. Samples collected from this coalfield were analyzed using low-temperature ashing plus X-ray diffraction analysis, scanning electron microscopy in combination with energy-dispersive X-ray spectrometry, X-ray fluorescence spectrometry, and inductively coupled plasma mass spectrometry. The investigated coal is of subbituminous A to high volatile bituminous rank (0.50–0.56% R o,ran ) and has a low sulfur content (0.25% on average). The mineral assemblage of the coal is dominated by kaolinite, illite and expandable clays, and quartz, with a trace of albite. In comparison with low-rank coals worldwide, the No. 19-2 Coal is enriched in Cs, V, and Mo. The minerals and elements in the coal and its roof and floor strata were mainly derived from the Mesozoic (Jurassic-Lower Cretaceous) intermediate-felsic volcanic rocks surrounding the coal basin. The parting within the coal seam is identified as a tonstein (bed of altered volcanic ash) based on its mineral composition, dominantly of vermicular and book-like kaolinite (plus smectite, high-temperature quartz, sanidine, apatite, and ilmenite), and its persistent distribution throughout the coal deposit. Based on these features and its chemical composition, this tonstein is deduced to have been derived from a Paleogene intermediate-felsic volcanic ash, which is characterized by some adakitic signatures of trace elements, and terrigenous materials. Normalized to the upper continental crust, the investigated samples (particularly the tonstein layer) show positive Eu anomalies inherited from the source rocks. This is in contrast to the coals, host rocks, and tonsteins with intermediate-felsic compositions in many other coal deposits, which are generally characterized by negative Eu anomalies. Geochemical and mineralogical features also indicate that the sedimentary materials of the tonstein, and, to a lesser extent, the floor horizon, were of aeolian origin, but those of most coal plies and roof strata were the result of aqueous deposition. [ABSTRACT FROM AUTHOR]

Clay-altered volcanic ash with highly-elevated concentrations of Nb(Ta), Zr(Hf), rare earth elements (REE), and Ga, is a new type of critical metal deposit with high commercial prospects that has been discovered in Yunnan Province, southwest China. Previous studies showed that the volcanic ashes had been subjected to hydrothermal fluids, the nature of which, however, is not clear. Here we show that the volcanic ashes were originated from alkaline magmatism, followed by a continuous hydrothermal-weathering process. Heated meteoric waters, which were sourced from acidic rains and mixed with CO 2 from degassing of the Emeishan plume, have caused partial, but widespread, acidic leaching of Nb, Ta, Zr, Hf, REE, and Ga into ground water and residual enrichment of these elements, along with Al and Ti, in the deeply altered rocks. Subsequent alteration occurring under cooler, neutral or alkaline conditions, caused by water-rock interaction, resulted in precipitation of the leached critical metals in the deposit. Polymetallic mineralization of similar origin may be found in other continental regions subjected to explosive alkaline volcanism associated with deep weathering in humid conditions. [ABSTRACT FROM AUTHOR]

Unburned carbon (UC) in fly ash indicates inefficiency in combustion and may be an impediment to the beneficial use of fly ash or ash products in a variety of applications. The characteristics of the coal-derived UC are a function of the rank and type of the coal, as well as the size of the feed coal and the combustion conditions. At any coal rank, inertinite macerals are inherently more difficult to combust than the associated vitrinite, and some will have a tendency to appear in the fly ash more or less unchanged from their appearance in the feed coal. The nature of UCs resulting from vitrinite is dependent upon the coal rank. Low-rank huminite/vitrinite will tend to form an isotropic char; bituminous vitrinite will appear as isotropic and anisotropic cokes; and anthracite vitrinite, naturally anisotropic, is observed as partially combusted vitrinite fragments in the ash. The absorption of air entraining agents by UCs limits the use of high-UC fly ashes as a Portland cement substitute, with both standards organizations and regulatory bodies imposing limits on the acceptable UC concentrations. UC in fly ash can be used to adsorb organic compounds (such as phenols, dyes, herbicides, polychlorinated biphenyls, and petroleum constituents) and to capture trace elements (particularly Hg) from flue gas. UCs can also be used as sources of activated carbons, manufacture of graphite, and cokes in the metallurgical industry, as well as a source of carbon to feed back into the boiler. Beneficiation of fly ash to segregate relatively UC-free or UC-rich splits for beneficial re-use can be done by size classification, electrostatic separation, and froth flotation, as well as density separation, acid digestion, and incipient fluidization. Thermal processing may also be used to burn off the UC, leaving a relatively UC-free fly ash as the product. [ABSTRACT FROM AUTHOR]

Improving safety and productivity are two of the biggest technical and operational challenges facing both the international and Australian coal mining industries. Hundreds of rock-related fatalities have occurred in Australian underground coal mines in the last three decades. Coal burst is defined as dynamic rock failure involving a sudden release of strain energy stored within the rock mass due to the disturbance of an unstable state of equilibrium, leading to high safety and productivity risks in the mining industry with the potential to cause multiple fatalities. It has been identified as one of the critical and longstanding engineering problems in underground coal mines. While there is now an extensive database available worldwide on coal burst phenomena, the international mining community still lacks clear scientific understanding of the causes and failure mechanisms of coal burst. This paper reviews the current knowledge and understanding of coal burst phenomena. There are a number of important considerations that need to be discussed to explore the origin and the source of the coal burst mechanism. Foremost amongst these is a critical assessment of the geological and mining factors, followed by in-depth evaluation of the contributing mechanisms. The discussion is extended with further comments on the roles and significance of energy, loading and gas, by identifying the current knowledge gaps. Based on that, the authors have identified future research needs and priorities for the coal burst management and control. An enhanced understanding of the driving mechanisms is essential for delivering reliable coal burst risk management and mitigation strategies. [ABSTRACT FROM AUTHOR]

Rare metals in coal deposits have attracted much attention in recent years because of their potential economic significance. This paper reports the abundance and enrichment origin of rare metals in the Late Permian coals (K1 and K2 Coals) of the Moxinpo Coalfield, Chongqing, southwestern China. The K1 Coal is characterized by highly-elevated concentrations of U-Re-V-Cr-Se and Nb(Ta)-Zr(Hf)-REE assemblages; the latter assemblage is also enriched in the K2 Coal. The high temperature ash (815 °C) of the K1 Coal is enriched in V, Cr, Se, Re, U and REE; the ash of the K2 Coal, and also the floor strata of each seam, are enriched in REE, potentially making all of the units economically viable sources for these elements. The minerals in the K1 Coal are mainly represented by kaolinite, illite and mixed-layer illite/smectite, and pyrite, while the minerals in the K2 Coal consist mainly of kaolinite and tobelite [(NH 4 ,K)Al 2 (AlSi 3 O 10 )(OH) 2 ]. Authigenic roscoelite [K(V 3 + ,Al) 2 (AlSi 3 O 10 )(OH) 2 ] is commonly observed in the K1 Coal under the SEM, and was probably formed by interaction of kaolinite with V derived from permeating U-Re-V-Cr-Se-rich solutions during early diagenesis. The tobelite enriched in the K2 Coal was formed by reaction between kaolinite already present in the coal and NH 4 + derived from decomposition of the organic matter during hydrothermal alteration at a relatively high temperature. The mafic tuffs directly underlying the K1 Coal and containing limestone residual breccias not only served as the substrate for coal accumulation but also as the source of sediment from the uplifted areas around the coal basin. The latter is indicated by low Al 2 O 3 /TiO 2 ratios (from 10.09 to 14.24), positive Eu anomalies enrichment of medium rare earths (relative to upper continental crust), and detrital calcite of terrigenous origin. The highly-elevated concentrations of U-Re-V-Cr-Se assemblages in the coal were derived from exfiltrational hydrothermal solutions and were then deposited in a euxinic environment. The terrigenous materials in the K2 Coal, however, were derived from felsic-intermediate rocks at the top of the Kangdian Upland, although the elevated concentrations of Nb(Ta)-Zr(Hf)-REE assemblages are attributed to the input of hydrothermal solutions. [ABSTRACT FROM AUTHOR]

Plerospheres play a positive role in reducing particulate matter emissions, Br and U to the atmosphere, may assist in the synthesis of fly ash-based zeolites, and serve as a substrate to produce industrial grade multiwalled carbon nanotubes. Optical and electron microscopy and laser granulometry have been used to evaluate the nature and origin of char plerospheres in two pulverized fuel (p.f.) fly ashes and one fluidized bed fly ash derived from Bokaro and Jharia coals (Jharkhand, India). The influence of plerospheres on the particle size distribution of the fly ashes was also assessed, including the potential for fragmentation of the char shell during ultrasonic dispersion associated with laser granulometry. Char plerospheres were found to be common in one of the p.f. fly ashes (Chandrapura). Microscopic study shows that these are post-combustion morphotypes resulting from the infilling of the open-hollow-porous char particles by glassy morphotypes, and in this case should be classified as char pseudoplerospheres. Their formation is also related to the coal composition and the combustion conditions; the coal must contain vitrinite and low-reflectance semifusinite macerals that are able to produce open-hollow-porous char morphotypes, and the feed must be pulverized and heated in such a way that small glassy spheres are formed. Experiments using ultrasonic dispersion resulted in a shift from trimodal to bimodal particle size distribution for the Chandrapura ash, due to the fragmentation of the char plerospheres and release of the glassy spheres contained within them. It may therefore be expected that some particle size-related utilization-friendly properties of fly ashes containing char pseudoplerospheres could change during handling and with time. [ABSTRACT FROM AUTHOR]

The occurrence of phosphorus minerals in coal is common, and its study is mainly related with the metallurgical coke making. Large amounts of phosphorus are emitted from coal and biomass combustion units and less direct methods, such as carbon black, are used for tracking stationary combustion sources of phosphorus. During the study of fly ash from coal burning power plants in the state of Jharkand, India, using XRD, SEM/EDS, XRF, ICP-MS and leaching tests, it was found that P-bearing spheres have unique visual characteristics. Therefore, this study is thought to represent the first time that P-spheres in coal fly ash are described and herein named as “phosphospheres”. To complement their characterization and how they form other fly ash types such as Quercus suber cork and chicken litter fly ashes were also studied using SEM. Under the SEM the phosphospheres are brighter than the associated aluminosilicate spheres, they may show a spongy (or “punctuated”) structure, have a high P-peak in the EDS profile, and their cross-sections typically show a “pomegranate” texture resulting from immiscible silicate and phosphate melts and the segregation of the P when the glassy matrix is still in a fluid stage. Therefore, with these unique characteristics, phosphospheres are easily recognized, and may be used as a direct method for phosphorus tracking. [ABSTRACT FROM AUTHOR]

Coal burning power plants in the state of Jharkand, India, are facing the problem of fly ash landfilling and their economic and environmental impact. However, fly ash may be used in civil engineering constructions, including as geoliners for municipal wastes landfilling, however in this case the groundwater contamination should be taken in consideration. In this work a combination of analytical techniques is used to study the nature, composition and potential environmental impact of Fe-bearing morphotypes (ferrospheres) in fly ash from thermal power plants fed with coals from Bokaro and Jharia coalfields (Jharkand, India). The results show that the feed coals are sulfur-poor and ash-rich, dominated by quartz, clays and minor portions of Fe-bearing carbonates, such as siderite. Pyrite was not identified. Although iron is present in the fly ashes in significant proportions (from 2.7 wt.% to 4.5 wt.%), equivalent to an Fe 2 O 3 content ranging from 3.5 wt.% to 5.8 wt.%, mineral phases such as magnetite and hematite are only present in minor proportions, or below detection limits of the XRD analyses. Iron in the ferrospheres occurs as massive or dendritic crystals, or as finely dispersed crystals trapped inside a glassy aluminosilicate matrix resulting from the release of iron oxide plumes into the aluminosilicate melt. In addition to these phases, iron also occurs as a component of the glass that makes up most of the fly ash materials. Finally, the contaminant potential of groundwater by the fly ash iron is negligible. [ABSTRACT FROM AUTHOR]

The chemical, mineralogical, petrographic and textural characteristics of fly ashes from one fluidized-bed and two pulverized-fuel power stations in India, have been evaluated by a range of complementary methods, including optical and electron microscopies, laser granulometry, quantitative X-ray diffraction, X-ray fluorescence spectrometry and inductively-coupled plasma techniques. Mineralogical and geochemical analyses have also been carried out on the feed coals from the respective power stations, and the results were used to evaluate the changes produced during different combustion processes. Differences in particle size and shape for the ashes, and also differences in ash petrology and mineralogy, have been related to differences in the mineral matter of the feed coals, and to the milling characteristics and combustion temperatures in the different power plants. There is a potential of using these fly ashes as geoliner because of their fine texture and low permeability. Leaching tests have also been carried out on the fly ashes, as a basis for assessing the potential for adverse impacts on groundwater systems. The materials were blended with bentonite to decrease the permeability further. The major and trace element compositions of these ashes were determined. Most of the elements studied were leached in lower concentrations than averages for the same elements from European fly ashes. It is thus expected that these ashes will not provide significant source of additional contamination to permeating water if they are used with bentonite as geoliner material. [ABSTRACT FROM AUTHOR]

This paper investigates the mineralogical and geochemical compositions of the Pennsylvanian coal in the Hailiushu Mine, Daqingshan Coalfield, neighboring previously-reported Al (Ga, REE) ore deposits (including the Adaohai Mine in the same coalfield and deposits in the Jungar Coalfield), using optical microscopy, field emission-scanning electron microscopy, X-ray fluorescence, and inductively coupled plasma mass spectrometry. The mineralogical and geochemical compositions in the coal were primarily controlled by the sediment-source region during peat accumulation, and by epigenetic acid hydrothermal solutions. The Hailiushu coal was deposited in a sub-depression (intermontane basin) in the inner part of the orogenic belt, with a sediment-source region composed mainly of Cambrian–Ordovician strata and Archaean metamorphic rocks. The minerals in the coal from the Hailiushu Mine dominantly consist of kaolinite, with minor amounts of quartz, sulfide and selenide minerals (including chalcopyrite, selenian galena, galena, sphalerite, clausthalite, and siegenite), aluminophosphates, and rhabdophane. The coal is enriched in SiO 2 (17.05% on average), TiO 2 (0.60%), Al 2 O 3 (13.71%), Zr (289 μg/g), Hf (7.09 μg/g), and to a lesser extent, F, Sc, V, Cu, Ga, Se, Y, Nb, Mo, Cd, Sn, La, Ta, W, Hg, Pb, Bi, and Th. Titanium largely occurs in the kaolinite. Elements such as Cu, Se, Sn, Hg, Pb, and Bi in the coal mainly occur in sulfide and/or selenide minerals. Zirconium, Hf, and Nb were largely derived from the sediment source region. The substitution of Ti for Al in kaolinite, the corrosion of previously-formed zircon, anatase, and quartz, and the enrichment of middle rare earth elements in the coal were caused by the epigenetic acid hydrothermal solutions. [ABSTRACT FROM AUTHOR]

The study on rare metals in coal and coal-bearing strata is a hot point issue in the field of coal geology. Rare metals that could be highly-enriched in coal and coal-bearing strata and thus can be industrially utilized include Li, Sc, Ti, V, Ga, Ge, Se, Zr, Nb, Hf, Ta, U, rare earth elements (lanthanides and Y), and noble metals. In this paper, the geological origin, modes of occurrence, and evaluation methods for coal-hosted rare metal deposits including Ge, Ga, U, Nb, rare earth element ore deposits are reviewed. The study on coal-hosted rare metal ore deposits can not only provide important evidence of coal geochemistry and coal mineralogy for coal formation origin, coal-seam correlation, coal basin formation and epigenetic deformation, regional geology-evolution, and sudden geological event, but also are practically significant for the development of coal circular economy, environmental protection during coal utilization, and for the security of national rare metal resources. [ABSTRACT FROM AUTHOR]

Abstract: The Late Permian coals from the Huayingshan Coalfield of southwestern China are significantly enriched in Zr (695μg/g), Nb (75.9μg/g), Se (6.99μg/g), Hf (10.1μg/g), and rare earth elements and Y (1423μg/g). Previous studies showed that the sediment-source region for these coals was the Kangdian Upland, which was formed at an early stage of the late Permian Period. The source rocks have a basalt composition, and those studies attributed the enrichment of the above high field strength elements (HFSEs) to derivation from the Kangdian Upland. Geochemical and mineralogical data presented in this study show that the dominant sediment-source regions for the coal and roof strata of the Huayingshan Coalfields are the Dabashan Uplift, Hannan Upland, and Leshan–Longnvsi Uplift. The highly-elevated concentrations of HFSEs in the coals are due to hydrothermal fluids. Three tonstein layers derived from alkali rhyolite were identified. These tonsteins are characterized by highly-enriched HFSEs and by strong negative Eu anomalies in the rare earth element distribution patterns. The major carriers of the rare earth elements in the coal are rhabdophane and silicorhabdophane, the latter of which is also enriched in Zr. Zirconium, however, mainly occurs in zircon. Rhabdophane and silicorhabdophane in the coal are mainly distributed along the bedding planes and occur as cell-fillings. Zircon in the coal occurs as cell-fillings and is of authigenic origin. Anatase in the partings and coals contains Nb, and occurs as fracture-filling and colloidal forms. The modes of occurrence of the above minerals indicate that they were derived from hydrothermal fluids. Mercury and Se mainly occur in sulfide minerals (pyrite and marcasite). [Copyright &y& Elsevier]

Abstract: This paper reports the mineralogical and geochemical compositions of the Late Permian C2 and C3 coals (both medium volatile bituminous coal) from the Xinde Mine, near Xuanwei in eastern Yunnan, which is located close to the area with the highest female lung cancer mortality in China. The two coals are characterized by high ash yields and low sulfur contents. Three factors, including sediment-source region, multi-stage volcanic ash generation, and multi-stage hydrothermal fluid injections, were responsible for variations in the geochemical and mineralogical compositions of the Xinde coals. Trace elements, including V, Sc, Co, Ni, Cu, Zn, Se, Zr, Nb, Hf, and Ta, are enriched in the coals and were mainly derived from the sediment-source Kangdian Upland region. Major minerals in the samples of coal, roof, floor and non-coal sediment partings include quartz, kaolinite, and chamosite, as well as interstratified illite/smectite and anatase. Chamosite in the coal was derived from reactions between kaolinite and Fe–Mg-rich hydrothermal fluids. However, chamosite in the roof strata was directly precipitated from Fe–Mg-rich hydrothermal fluids or was derived from the alteration of precursor minerals (e.g., biotite) by hydrothermal fluids. Quartz in some samples is very high, especially in the roof strata of the C2 and C3 coal. Such high quartz, along with minor minerals including pyrite, chalcopyrite, sphalerite, calcite, celestite, vanadinite, barite, clausthalite and silicorhabdophane, were derived from multi-stage hydrothermal fluids. The floors of both the C2 and C3 coal seams are fully-argillized fine-grained tuffaceous claystone and the immediate roof of the C2 coal is argillized coarse-grained tuff. The original materials of the floors and roofs of these coal seams were high-Ti alkali basaltic volcanic ashes, as indicated by high TiO2, Nb, and siderophile elements, and the distribution patterns of rare earth elements. Two intra-seam tonstein layers in the C3 coal were identified based on their lateral persistence, mineralogical mode of occurrence and composition, as well as their elemental composition. The tonsteins are dominated by kaolinite, with minor quartz and possibly mixed-layer illite/smectite. Both tonsteins were derived from dacitic magma. The ratios of Nb/Ta, Zr/Hf, and U/Th are much lower in tonsteins than in the adjacent coal benches, which is attributed to the hydrothermal leaching. [Copyright &y& Elsevier]

Abstract: This article addresses the fundamental difference between coal rank and coal type. While theoretically settled long ago as being different aspects of coal systems science, the two concepts are still often confounded. In recent years, this has resulted in the publication of several works stating that coal type changes with coal rank. Coal type refers solely to coals' depositional origin and the maceral–mineral admixture resulting from that origin. Coal types typically fall in to two categories: humic coals, developed from peat, and sapropelic coals, developed from organic mud. Either type may be allocthonous or autochthonous, and within types, further refinement of depositional environment can be made. Coal rank refers to the changes in geochemistry and resultant changes in reflectance caused by increasing thermal maturity of the coal. Thus, it provides an overprint of maturity on existing coal types. With proper techniques, such as use of crossed polars and etching, maceral forms can be differentiated even at high ranks, and the original coal type determined. [Copyright &y& Elsevier]

Abstract: The Late Permian coals in the Heshan Coalfield of southern China are preserved within marine carbonate successions and characterized by super-high organic sulfur (5.13–10.82%). Minerals identified in the coals include quartz, kaolinite, illite, mixed layer illite/smectite, albite, pyrite, marcasite, calcite, and dolomite, along with trace amounts of smectite, fluorite, strontianite, REY-bearing carbonate minerals, jarosite, and water-bearing Fe-oxysulfate. The coals are very rich in trace elements including F (up to 3362μg/g), V (up to 270μg/g), Se (up to 24.4μg/g), Mo (up to 142μg/g), U (up to 111μg/g), and, to a lesser extent, Sr, Y, Zr, Nb, Cd, Cs, heavy rare earth elements, Hf, Ta, W, Hg, and Th. Previous studies attributed the high organic sulfur and elevated trace elements to the seawater influence or the formation of soil horizons before the accumulation of peat in the basin. However, mineralogical and geochemical data presented in this study have shown that the sediment-source region and multi-stage hydrothermal fluids are the dominant influences on the mineralogical composition and elevated trace elements in the coal, although seawater influence also contributed to the composition of the mineral matter. For example, a large proportion of the quartz and clay minerals, as well as almost all the albite, in both the coal benches and the parting mudstones were derived from detrital materials of terrigenous origin in the Yunkai Upland. High concentrations of lithophile trace elements were also derived from the sediment source region. Minerals including fluorite, calcite, dolomite, strontianite, and REY-bearing carbonate minerals were derived from multi-stage hydrothermal activities. High concentrations of V, Mo, and U that occur through the coal seam sections were probably derived from hydrothermal solutions during peat accumulation or at the early diagenetic stages. The hydrothermal fluids also corroded the syngenetically-formed minerals (quartz, albite, and pyrite) and caused re-distribution of lithophile elements from partings to the underlying coal benches, resulting in higher key element ratios (Yb/La, Nb/Ta, and Zr/Hf) and more abundant heavy rare earth elements in the coal benches than in the immediately overlying partings. [Copyright &y& Elsevier]

The Herrin coal (Western Kentucky No. 11) "ragged edge" is composed of peculiar organic materials, including voids, which defy conventional maceral classification. These materials seem to have originated from natural pyrolysis caused by hot fluids migrating through low-rank coal. However, the observed petrographic patterns and the reflectance analysis were not enough to confirm this hypothesis. In order to obtain for the first time an approximate composition and temperature value of the fluids that may have thermally affected the Herrin coal, the origin of the "ragged edge" of the Herrin coal seam was studied via a combination of analytical techniques mainly focused on the carbonates including optical microscopy, cathodoluminescence, X-ray fluorescence, X-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy, electron microprobe, and Raman microspectroscopy. The sum of indicators is collectively considered evidence that ascending hot fluids thermally affected the coal. These indicators include the ambient reflectance increase due to forced coalification; liptinite fading and "cryptic liptinite" formation at the bottom of the coal seam; the carbonate stable isotopes model temperature that indicates a range of 150 °C to 200 °C, and the Raman spectra proxy of the thermally affected particles indicating a temperature between 160 and 220 °C. • The origin of the "ragged edge" of the Herrin coal seam was studied via a combination of analytical techniques. • The sum of indicators is collectively considered evidence that ascending hot fluids thermally affected the coal. • The carbonate stable isotopes model temperature that indicates a range of 150 °C to 200 °C and the Raman spectra a temperature between 160 and 220 °C. [ABSTRACT FROM AUTHOR]

Coal, one of the most complex geological materials, consists of organic and mineral matter, the latter including crystalline minerals, non-crystalline mineraloids, and elements with non-mineral associations. Overall, the modes of occurrence of elements in coal are classified into organic, mineral, and intimate organic associations, the latter including those adsorbed on to the surface of organics, dissolved in pore waters, and hosted in very fine-grained minerals (sub-micro- or nano-minerals) encased in or shielded by the organic matter of coal. Mineral associations, defined as elements associated with minerals are straightforward; however, confusion about organic and intimate organic associations of elements usually arise in the literature. Understanding organic, mineral, and intimate organic associations of elements is important not only because non-mineral elements and, to a lesser extent, elements associated with fine-grained minerals, play a significant role in affecting the utilization of coal, but also such modes of occurrence of elements provide useful geochemical information on coal formation and coal-bearing basin evolution. With a few exceptions (such as Cd, Nb, Ta, Zr, and Hf), most elements determined in coal, particularly in low-rank coal, have varying-degrees of organic association. In this paper, we review the definition of associations of non-mineral elements in coal, as well as their methods of determination, and then review the associations of selected elements including environmentally-sensitive (e.g., S, As, U, and Hg) and critical elements, the latter of which drive some of the significant advancements in technology and energy efficiency in the world today (e.g., rare earth elements and Y, Ge, and U), and some major elements (e.g., Ca, Mg, Fe, Al, and Ti) that largely occur in non-mineral forms in low-rank coals. • The modes of occurrence of elements in coal are classified into organic, mineral, and intimate organic associations • The intimate organic associations include those adsorbed on to the surface of organics, dissolved in pore waters, and hosted in very fine-grained minerals. • Most elements determined in coal have varying-degrees of organic association. [ABSTRACT FROM AUTHOR]

Bicuspid aortic valve (BAV) is the most common congenital heart malformation in adults but can also cause childhood-onset complications. In multicenter study, we found that adults who experience significant complications of BAV disease before age 30 are distinguished from the majority of BAV cases that manifest after age 50 by a relatively severe clinical course, with higher rates of surgical interventions, more frequent second interventions, and a greater burden of congenital heart malformations. These observations highlight the need for prompt recognition, regular lifelong surveillance, and targeted interventions to address the significant health burdens of patients with early onset BAV complications., Competing Interests: Conflicts of Interest None.

The extraction of sulphur produces a hematite-rich waste, known as roasted pyrite ash, which contains significant amounts of environmentally sensitive elements in variable concentrations and modes of occurrence. Whilst the mineralogy of roasted pyrite ash associated with iron or copper mining has been studied, as this is the main source of sulphur worldwide, the mineralogy, and more importantly, the characterization of submicron, ultrafine and nanoparticles, in coal-derived roasted pyrite ash remain to be resolved. In this work we provide essential data on the chemical composition and nanomineralogical assemblage of roasted pyrite ash. XRD, HR-TEM and FE-SEM were used to identify a large variety of minerals of anthropogenic origin. These phases result from highly complex chemical reactions occurring during the processing of coal pyrite of southern Brazil for sulphur extraction and further manufacture of sulphuric acid. Iron-rich submicron, ultrafine and nanoparticles within the ash may contain high proportions of toxic elements such as As, Se, U, among others. A number of elements, such as As, Cr, Cu, Co, La, Mn, Ni, Pb, Sb, Se, Sr, Ti, Zn, and Zr, were found to be present in individual nanoparticles and submicron, ultrafine and nanominerals (e.g. oxides, sulphates, clays) in concentrations of up to 5%. The study of nanominerals in roasted pyrite ash from coal rejects is important to develop an understanding on the nature of this by-product, and to assess the interaction between emitted nanominerals, ultra-fine particles, and atmospheric gases, rain or body fluids, and thus to evaluate the environmental and health impacts of pyrite ash materials., (Copyright © 2012 Elsevier B.V. All rights reserved.)