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The mineralogical and geochemical compositions of the Lopingian coals from an exploratory drill core (ZK4-1) in the Zhongliangshan Coalfield, southwestern China are reported in this paper. The Zhongliangshan coals are medium volatile bituminous in rank (random vitrinite reflectance, average 1.38%), characterized by a medium-ash yield (26.84%) and high sulfur content (3.38%). Minerals in the Zhongliangshan coals are mainly composed of clay assemblages (kaolinite, the illite/smectite mixed layer (I/S) and chamosite), pyrite, quartz, carbonate minerals (calcite, marcasite, ankerite, and dolomite), and anatase, followed by rutile, jarosite, natrojarosite, bassanite, gypsum and K-feldspar, with traces of apatite, rhabdophane and barite. Compared with the average concentrations of the world hard coals, some trace elements including Li, V, Co, Cu, Se, Y, Zr, Nb, rare earth elements (REE), Cd, Ta, Hf and Hg, are enriched in the Zhongliangshan coals. The modes of occurrence of chamosite, barite, rhabdophane, quartz and calcite in the Zhongliangshan coals indicate that the coals have probably been affected by the injection of low-temperature hydrothermal fluids. Based on the concentrations of Sc, V, Cr, Co, Ni, Cu and Zn, the ratios of Al2O3/TiO2 and the upper continental crust-normalized rare earth element and yttrium (REY) distribution patterns of the Zhongliangshan coals, the dominant sediment source regions are the Leshan-Longnvsi Uplift, Hannan Upland, and Dabashan Uplift, with a small proportion of terrigenous materials from the Kangdian Upland. The K7 and the upper portion of K1 coals have the potential as raw materials for the recovery of REY. [ABSTRACT FROM AUTHOR]

Abstract: Aluminum-hydroxide (boehmite)-rich Pennsylvanian coals of high volatile A bituminous rank were found previously in the Jungar Coalfield, Inner Mongolia, China. This paper reports new results on 48 bench samples of the CP2 coal from the adjacent Adaohai Mine, Daqingshan Coalfield, Inner Mongolia, and provides new insights into the origin and modes of occurrence of the minerals and elements present in the CP2 coal. Compared to the same coal in the adjacent mines, the CP2 coal in the Adaohai Mine has a higher rank (Ro, ran =1.58%), which is attributed to igneous intrusions during the Late Jurassic and Early Cretaceous Epochs. The proportion of inertinite (35.3%) in the coal is higher than that in other Late Paleozoic coals in northern China but lower than that in the Jungar coals. Minerals in the CP2 coal include diaspore, boehmite, gorceixite, calcite, dolomite, siderite, clay minerals (kaolinite and ammonian illite), and trace amounts of anatase, fluorapatite, quartz, and pyrite. Based on mineral proportions in the coal bench samples, the CP2 coal may be divided into four Zones (I to IV) from bottom to top. The major mineral in Zones I and IV is kaolinite. Zones II and III are mainly composed of ammonian illite, diaspore, boehmite, gorceixite, calcite, dolomite, and siderite. Diaspore-, boehmite-, and gorceixite-forming materials were derived from oxidized bauxite in the weathered crust of the Benxi Formation in the sediment-source region during peat accumulation. However, gorceixite may have formed earlier than diaspore; the diaspore was derived from gibbsite that was subjected to dehydration by the heat of the igneous intrusions. The ammonian illite may have been formed at a relatively high temperature by interaction of kaolinite with nitrogen released from the organic matter in the coal during metamorphism caused by the igneous intrusion. The calcite and dolomite occur as epigenetic cell- and fracture-fillings and were probably derived from the igneous fluids. Compared to the common Chinese and world coals, the CP2 coal is enriched in CaO (1.69%), MgO (0.32%), P2O5 (0.214%), F (207μg/g), Ga (16.3μg/g), Zr (446μg/g), Ba (276μg/g), Hg (0.33μg/g), and Th (12.4μg/g), but has a lower SiO2/Al2O3 ratio due to the higher proportions of diaspore, boehmite, and gorceixite in the coal. The F occurs mainly in gorceixite and fluorapatite. The major carriers of Ga are diaspore and kaolinite but not gorceixite. Barium mainly occurs in gorceixite and barite. Mercury was probably derived from the igneous intrusion and is distributed in both the organic matter and the minerals. The elements are classified into five associations by cluster analysis, Groups A, B, C, D, and E. Group A represents a REE-Be-Y-Se-Ga-Ge-Sc-In-Pb-Bi-Nb-Ta-TiO2-W-Hg-Sb-Zr-Hf-Th-U association. Most of the elements in Group A are lithophile elements that occur in aluminosilicate minerals. Group B (Sn-Te-Zn-Cd-V-As-Cr-Cu-Mo-Ni-Re) is weakly correlated with ash yield and is associated with unidentified trace sulfide minerals. Elements in Group C (Ad-Na2O-Al2O3-SiO2- Li-K2O-Rb-Cs-Tl association) probably occur in the clay minerals and diaspore. Group D consists of P2O5, Ba, F, Sr, S, and Cl, and with the exception of S, they occur in minerals (gorceixite and fluorapatite). Oxides of Fe2O3-MnO-CaO-MgO make up Group E and mainly occur in the carbonate minerals. The coals are enriched in light REEs and the LREEs–HREEs have been highly fractionated, with an average (La/Yb) N of 8.71. The heavy REEs in the coals have a stronger organic affinity than the LREEs. [Copyright &y& Elsevier]