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Geological controls on the distribution of REY-Zr (Hf)-Nb (Ta) enrichment horizons in late Permian coals from the Qiandongbei Coalfield, Guizhou Province, SW China
International Journal of Coal Geology ( IF 5.6 ) Pub Date : 2020-11-01 , DOI: 10.1016/j.coal.2020.103604
Baoqing Li , Xinguo Zhuang , Xavier Querol , Natalia Moreno , Patricia Córdoba , Yunfei Shangguan , Linjian Yang , Jing Li , Feng Zhang

Abstract 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.

中文翻译:

贵州省黔东北煤田晚二叠世煤中REY-Zr(Hf)-Nb(Ta)富集层位分布的地质控制

摘要 我国西南地区部分煤田晚二叠世煤中REY(稀土元素和钇)-Zr(Hf)-Nb(Ta)组合异常富集已被广泛研究,但该组合的地质控制因素是仍在辩论中。本研究报告了从贵州省黔东北煤田玉带和金旗煤矿采集的煤和非煤岩的矿物学和地球化学特征,以阐明 REY-Zr (Hf)-Nb (Ta) 富集分布的地质控制地平线。研究的煤显示出相当一致的高岭石粘土矿物组合,以及不同数量的石英、石膏、黄铁矿和方解石。值得注意的是,煤中异常富含 REY、Nb、Ta、Zr 和 Hf,并富含其他不相容元素(例如 Ga、Th、和你)。磷酸盐(例如,萤石)和在较小程度上的锆石是 REY 的主要载体。锆和 Hf 主要掺入锆石,然后是锐钛矿,后者是 Nb 和 Ta 的主要载体。碎屑材料来自喷发的长英质火山灰,类似于过碱性流纹岩成分,以及峨眉山大型火成岩省 (ELIP) 玄武岩的侵蚀材料。所研究的煤中 REY-Zr (Hf)-Nb (Ta) 组合的高度增加是由于长英质火山灰的输入,其中高酸性水溶液使这些元素变得可移动并重新分布。两种地质过程都控制着 REY-Zr (Hf)-Nb (Ta) 富集层的分布。高酸性溶液可能来自泥炭沼泽的氧化和与火山活动有关的酸雨。煤灰中REY、Zr、Nb的浓度超过了相应的临界品位;因此,这些煤可以被认为是 REY-Zr (Hf)-Nb (Ta) 组合的非常有前途的原材料来源。
更新日期:2020-11-01
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