Geological and geochemical characteristics in the paleo-weathering crust sedimentary type REE deposits,western Guizhou,China |
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| Institution: | 1. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;2. Graduate University of Chinese Academy of Sciences, Beijing 100049, China;3. Berkeley Geochronology Center, Berkeley, CA 94709, USA;1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China;2. Department of Earth and Environmental Sciences, University of St. Andrews, St. Andrews KY16 9AL, UK;3. Centre for Exploration Targeting, School of Earth and Environment, University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia;4. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China;5. College of Earth Science, Chengdu University of Technology, Chengdu 610059, China;1. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, PR China;2. Institute of Multipurpose Utilization of Mineral Resources, Chinese Academy of Geological Sciences, Chengdu 610041, PR China;3. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, PR China;4. Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, PR China;5. Chengdu Institute of Geology and Mineral Resources, Geological Survey of China, Chengdu 610081, PR China;1. Department of Natural Resources and the Environment, University of New Hampshire, James Hall, Durham, NH, 03824, USA;2. School of Earth Sciences, University of Bristol, Wills Memorial Building, Bristol, BS8 1RJ, UK;3. Department of Crop and Soil Sciences, Oregon State University, Corvallis, OR, 97330, USA |
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| Abstract: | A supergene REE deposit closely interrelated with the weathering of the Emeishan basalt formation was produced in the Xuanwei formation, the overlying stratum of the late Permian Emeishan basalt formation in West Guizhou, China. The host strata consist primarily of offwhite kaolinite clay rock and/or grayish black carbonaceous shale. Mineralogical analyses reveal that kaolinites are the major minerals in REE ores with small amounts of smectite, illite, boehmite, hornblende, pyrophyllite, calcite, dolomite and/or iron-bearing minerals, with a certain proportion of feldspar, quartz crystal debris and noncrystal debris. Geochemical analyses reveal high enrichment of trace elements like Cu, Nb, Ta, Zr and Hf. The host strata feature considerable lithological variability, close interrelation of the REE grade with the lithology and uneven spatial distribution of the REE ores, which are mostly found in Lufang, Maojiaping and Zhangsigou profiles of Weining County and can be as thick as 20 m. Of the five stratigraphic profiles, 48% have their whole-rock ∑REE higher than 1000 ppm. The REE in this framework consists primarily of ion adsorbed phases and REE-rich residual independent mineral phases. Comprehensive analyses suggest that the source may not only include the Emeishan basalt, but the intermediate acid volcanic rocks evolved from the Emeishan basalt in the later periods; the hydrothermal alteration subsequently imposed on the host strata might have boosted the mineralization of the rare earth. The preliminary genetic model should have been: the denudation product from the weathering of the parent rock was migrated to the sea-continental margin at the continent side carrying huge quantities of REE with it and was preserved by the quick marine transgression. The host strata consist primarily of kaolinite clay rock and/or carbonaceous shale, which are so far believed to be a sedimentary type REE deposit closely interrelated with weathering effect. |
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| Keywords: | Sedimentary type REE deposit Emeishan basalt Weathering Guizhou |
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