Multi-stage pyrite and hydrothermal mineral assemblage of the Hatu gold district (west Junggar,Xinjiang, NW China): Implications for metallogenic evolution |
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| Institution: | 1. Division of Geosciences and Environmental Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden;2. Boliden Mineral, Exploration Department, SE-776 98 Garpenberg, Sweden;1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China;2. Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China;3. Third Geological Survey Team, Henan Bureau of Geo-exploration and Mineral Development, Xinyang 464000, China;1. Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Avenida Bento Gonçalves, 9500, Bairro Agronomia, 91501-970 Porto Alegre, Rio Grande do Sul, Brazil;2. Departamento Nacional de Produção Mineral, Superintendência do Mato Grosso do Sul, Rua General Odorico Quadros, 123, 79020-260 Campo Grande, Mato Grosso do Sul, Brazil;3. Geological Survey of Brazil (CPRM), SUREG-GO, Rua 148, 485, Setor Marista, 74170-110 Goiânia, Goiás, Brazil;1. MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;2. National Key Laboratory of Remote Sensing Information and Image Analysis Technology, Beijing Research Institute of Uranium Geology, Beijing 100029, China;3. School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China;4. Yunnan Gold & Mineral Group Co., Ltd, Kunming 650224, China |
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| Abstract: | The Hatu, Qi-III, and Qi-V gold deposits in the Hatu–Baobei volcanic–sedimentary basin (west Junggar, Xinjiang) represent the proximal, middle, and distal parts of the Hatu gold district, respectively. Orebodies of these deposits mainly consist of Au-bearing quartz veins and altered host rocks with disseminated sulfide minerals. Six types of pyrite in these mines are studied here to illustrate ore-formation processes. Sedimentary pyrite, including framboidal and fine-grained pyrite, occurs in mudstone-bearing sedimentary rocks or altered volcanic–sedimentary rocks. Framboidal pyrite formed during redox changes in sedimentary layers. Hydrothermal pyrite contains five subgroups, from Py1 to Py5. Porous Py1 formed prior to gold mineralization, and is overgrown by Py2 that contains inclusions of sulfide minerals and native gold. Coarser Py3 coexists with arsenopyrite and native gold, and contains the greatest As concentrations. Gold and antimony are also preferentially concentrated in arsenian Py2 and Py3. The Au–As-deficient Py4 and Py5 formed during the post-ore process. There is a negative correlation between the As and S contents in Py1, Py2, and Py3, implying the substitution of sulfur by arsenic. Gold precipitated under relatively reducing condition in framboid- and graphite-bearing tuffaceous rocks. Cesium, Rb, Sr, La, Ce, Au, As, Sb, Cu, and Pb are concentrated in altered host rocks. The Au-bearing quartz veins and disseminated sulfide mineral orebodies were formed via a co-genetic hydrothermal fluid and formed during different stages. The variation of fO2 during fluid/rock interactions, and crystallization of arsenian pyrite were major factors that controlled gold precipitation. |
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