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Genesis of the supergiant Huayangchuan carbonatite-hosted uranium-polymetallic deposit in the Qinling Orogen,Central China
Institution:3. Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou 510640, China;1. School of Earth Science and Resources, Chang''an University, Xi''an 710054, China;2. Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;3. Guangdong Provincial Key Laboratory of Mineral Physics and Materials, 511 Kehua Street, Guangzhou 510640, China;4. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China;5. Department of Geology, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario P7B5E1, Canada;1. Department of Physics and Earth Sciences, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany;2. Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) Hannover, Stilleweg 2, D-30655 Hannover, Germany;3. National Office of Hydrocarbons and Mines (ONHYM), 5 Avenue Moulay Hassan, Rabat, Morocco
Abstract:The newly-discovered supergiant Huayangchuan uranium (U)-polymetallic deposit is situated in the Qinling Orogen, Central China. The deposit contains economic endowments of U, Nb, Pb, Se, Sr, Ba and REEs, some of which (e.g., U, Se, and Sr) reaching super-large scale. Pyrochlore, allanite, monazite, barite-celestite and galena are the major ore minerals at Huayangchuan. Uranium is mainly hosted in the primary mineral of pyrochlore, and the mineralization is mainly hosted in or associated with carbonatite dikes.According to the mineral assemblages and crosscutting relationships, the alteration/mineralization at Huayangchuan comprises four stages, i.e., pegmatite REE mineralization (I), main mineralization (II), skarn mineralization (III) and post-ore alteration (IV). Coarse-grained euhedral allanite is the main Stage I REE mineral, and the pegmatite-hosted REE mineralization (ca. 1.8 Ga) occurs mostly in the shallow-level of northwestern Huayangchuan, corresponding to the Paleoproterozoic Xiong'er Group volcanic rocks (1.80–1.75 Ga) in the southern margin of North China Block. Carbonatite-hosted Stage II mineralization contributes to the majority of U-Nb-REE-Ba-Sr resources, and is controlled by the Huayangchuan Fault. Stage II mineralization can be further divided into the sulfate mineralization (barite-celestite) (II-A), alkali-rich U mineralization (aegirine-augite + pyrochlore + uraninite + uranothorite) (II-B) and REE (allanite + monazite + chevkinite)-U (pyrochlore + uraninite) mineralization (II-C) substages. Stage II mineralization may have occurred during the Late Triassic Mianlue Ocean closure. Skarn mineralization contributed to the majority of Pb and minor U-REE (uraninite-allanite) resources at Huayangchuan, and is spatially associated with the Late Cretaceous-Early Jurassic (Yanshanian) Huashan and Laoniushan granites. We suggested that hydrothermal fluids derived from the Laoniushan and Huashan granites may have reacted with the Triassic carbonatites, and formed the Huayangchuan Pb skarn mineralization.The mantle-derived Triassic carbonatites may have been fertilized by the U-rich subducting oceanic sediments, and were further enriched through reacting with the Proterozoic U-REE-rich pegmatite wallrocks at Huayangchuan. Ore-forming elements were likely transported in metal complexes (F, PO43, CO32 and SO42), and deposited with the dilution of the complex concentration. This may have formed the distinct vertical mineralization zoning, i.e., sodic fenite-related alkali-U mineralization at depths and potassic fenite-related REE-U mineralization at shallow level.
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