TY - JOUR
T1 - Mineralogy and geochemistry of boehmite-rich coals: New insights from the Haerwusu Surface Mine, Jungar Coalfield, Inner Mongolia, China
AU - Dai, Shifeng
AU - Li, Dan
AU - Chou, Chen-Lin
AU - Zhao, Lei
AU - Zhang, Yong
AU - Ren, Deyi Y.
AU - Ma, Yuwen
AU - Sun, Yingying
N1 - Funding Information:
This research was supported by National Key Basic Research and Development Program (nos. 2003CB214607 and 2006CB202201), the National Natural Science Foundation of China (nos. 40672102 and 40725008). One of us (CLC) is grateful for a visiting professorship at the State Key Laboratory of Coal Resources and Safe Mining of CUMTB during the fall semester, 2007. Special thanks are given to the two anonymous reviewers and Dr. J. Hower for helpful comments on the manuscript.
PY - 2008/5/7
Y1 - 2008/5/7
N2 - Boehmite-rich coal of Pennsylvanian age was discovered earlier at the Heidaigou Surface Mine, Jungar Coalfield, Inner Mongolia, China. This paper reports new results on 29 bench samples of the no. 6 coal from a drill core from the adjacent Haerwusu Surface Mine, and provides new insights into the origin of the minerals and elements present. The results show that the proportion of inertinite in the no. 6 coal is higher than in other Late Paleozoic coals in northern China. Based on mineral proportions (boehmite to kaolinite ratio) and major element concentrations in the coal benches of the drill core, the no. 6 coal may be divided into five sections (I to V). Major minerals in Sections I and V are kaolinite. Sections II and IV are mainly kaolinite with a trace of boehmite, and Section III is high in boehmite. The boehmite is derived from bauxite in the weathered surface (Benxi Formation) in the sediment-source region. The no. 6 coal is rich in Al
2O
3 (8.89%), TiO
2 (0.47%), Li (116 μg/g), F (286 μg/g), Ga (18 μg/g), Se (6.1 μg/g), Sr (350 μg/g), Zr (268 μg/g), REEs (172 μg/g), Pb (30 μg/g), and Th (17 μg/g). The elements are classified into five associations by cluster analysis, i.e. Groups A, B, C, D, and E. Group A (ash-SiO
2-Al
2O
3-Na
2O-Li) and Group B (REE-Sc-In-Y-K
2O-Rb-Zr-Hf-Cs-U-P
2O
5-Sr-Ba-Ge) are strongly correlated with ash yield and mainly have an inorganic affinity. The elements that are negatively or less strongly correlated with ash yield (with exceptions of Fe
2O
3, Be, V, and Ni) are grouped in the remaining three associations: Group C, Se-Pb-Hg-Th-TiO
2-Bi-Nb-Ta-Cd-Sn; Group D, Co-Mo-Tl-Be-Ni-Sb-MgO-Re-Ga-W-Zn-V-Cr-F-Cu; and Group E, S-As-CaO-MnO-Fe
2O
3. Aluminum is mainly distributed in boehmite, followed by kaolinite. The high correlation coefficients of the Li-ash, Li-Al
2O
3, and Li-SiO
2 pairs indicate that Li is related to the aluminosilicates in the coal. The boehmite-rich coal is high in gallium and F, which occur in boehmite and the organic matter. Selenium and Pb are mainly in epigenetic clausthalite fillings in fractures. The abundant rare earth elements in the coal benches were supplied from two sources: the bauxite on the weathered surface of the Benxi Formation and from adjacent partings by groundwater leaching during diagenesis. The light rare earth elements (LREEs) are more easily leached from the partings and incorporated into the organic matter than the heavy REEs, leading to a higher ratio of LREEs to HREEs in the coal benches than in the overlying partings.
AB - Boehmite-rich coal of Pennsylvanian age was discovered earlier at the Heidaigou Surface Mine, Jungar Coalfield, Inner Mongolia, China. This paper reports new results on 29 bench samples of the no. 6 coal from a drill core from the adjacent Haerwusu Surface Mine, and provides new insights into the origin of the minerals and elements present. The results show that the proportion of inertinite in the no. 6 coal is higher than in other Late Paleozoic coals in northern China. Based on mineral proportions (boehmite to kaolinite ratio) and major element concentrations in the coal benches of the drill core, the no. 6 coal may be divided into five sections (I to V). Major minerals in Sections I and V are kaolinite. Sections II and IV are mainly kaolinite with a trace of boehmite, and Section III is high in boehmite. The boehmite is derived from bauxite in the weathered surface (Benxi Formation) in the sediment-source region. The no. 6 coal is rich in Al
2O
3 (8.89%), TiO
2 (0.47%), Li (116 μg/g), F (286 μg/g), Ga (18 μg/g), Se (6.1 μg/g), Sr (350 μg/g), Zr (268 μg/g), REEs (172 μg/g), Pb (30 μg/g), and Th (17 μg/g). The elements are classified into five associations by cluster analysis, i.e. Groups A, B, C, D, and E. Group A (ash-SiO
2-Al
2O
3-Na
2O-Li) and Group B (REE-Sc-In-Y-K
2O-Rb-Zr-Hf-Cs-U-P
2O
5-Sr-Ba-Ge) are strongly correlated with ash yield and mainly have an inorganic affinity. The elements that are negatively or less strongly correlated with ash yield (with exceptions of Fe
2O
3, Be, V, and Ni) are grouped in the remaining three associations: Group C, Se-Pb-Hg-Th-TiO
2-Bi-Nb-Ta-Cd-Sn; Group D, Co-Mo-Tl-Be-Ni-Sb-MgO-Re-Ga-W-Zn-V-Cr-F-Cu; and Group E, S-As-CaO-MnO-Fe
2O
3. Aluminum is mainly distributed in boehmite, followed by kaolinite. The high correlation coefficients of the Li-ash, Li-Al
2O
3, and Li-SiO
2 pairs indicate that Li is related to the aluminosilicates in the coal. The boehmite-rich coal is high in gallium and F, which occur in boehmite and the organic matter. Selenium and Pb are mainly in epigenetic clausthalite fillings in fractures. The abundant rare earth elements in the coal benches were supplied from two sources: the bauxite on the weathered surface of the Benxi Formation and from adjacent partings by groundwater leaching during diagenesis. The light rare earth elements (LREEs) are more easily leached from the partings and incorporated into the organic matter than the heavy REEs, leading to a higher ratio of LREEs to HREEs in the coal benches than in the overlying partings.
KW - ISGS
KW - Jungar Coalfield
KW - Trace elements in coal
KW - Coal
KW - Boehmite
KW - Minerals in coal
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U2 - 10.1016/j.coal.2008.01.001
DO - 10.1016/j.coal.2008.01.001
M3 - Article
SN - 0166-5162
VL - 74
SP - 185
EP - 202
JO - International Journal of Coal Geology
JF - International Journal of Coal Geology
IS - 3-4
ER -