关键词: 夏家店金矿床, 黑色岩系, 元素地球化学, 成矿环境

Abstract: The Xiajiadian gold deposit is located at the passive continental northern margin of the Yangtze Block in the Early Paleozoic and within the ZhashuiShanyang Basin. The black rock series of the Xiajiadian gold deposit consist of light-red siliceous rocks, blue-grey altered siliceous argillaceous rocks, gray-black thin-layer carboncaceous-siliceous slate, khaki argillite and black carbonaceous-siliceous argillaceous rocks. In this study, we carried out systematic analyses of the major and trace elements and REEs in the black rock series. The main component of the series was SiO2, the highest abundant component in the siliceous rocks. These rocks were significantly enriched in LILE and ore-forming elements (e.g. Sr, Ba, U, Cu, Zn, V, Au and Ag), whose contents reached several or even dozens of times higher than their crustal abundance. The North American shale-normalized REE patterns of the black rock series were left inclined and characterized by weak negative Ce and negative to positive Eu anomalies for the siliceous rocks, negative Ce and Eu anomalies for the argillite, and positive Eu anomalies for some minor carboncaceous-siliceous rocks. Combining the petrologic characteristics and tectonic settings, as well as characteristic parameter ratios and discrimination diagrams of major and trace elements and REEs, the results indicate that the diagenetic materials of these black rock series had diverse sources. The lower siliceous rocks are mainly products of hydrothermal sedimentation. They formed carboncaceous-siliceous rocks and argillite during the transformation from hydrothermal to normal sedimentation with added seawater and terrestrial materials. The black rock series in the Xiajiadian gold deposit are formed in a deep to semi-deep water retention and hypoxia basin at the continental margin belonging to the rift deposition area of passive continental margin of the Yangtze Block. The fertile black rock series of the Shuigoukou Formation in the Xiajiadian gold deposit are likely to be an important source bed with super high level enrichment of Au, Ag, Ni, Cu, Zn, V, Ba and other elements.

Key words: Xiajiadian gold deposit, black rock series, elemental geochemical characteristic, metallogenic environment