CHENG Peng-lin1, XIONG Wei2, ZHOU Gao3, HE Zhi-wei4
(1. The 115 Geological Team, Guizhou Bureau of Exploration and Development of Geology and Mineral Resources, Qingzhen 561400, China;
2. The 117 Geological Team, Guizhou Bureau of Exploration and Development of Geology and Mineral Resources, Guiyang 550018, China;
3. The 106 Geological Team, Guizhou Bureau of Exploration and Development of Geology and Mineral Resources, Zunyi 563000, China;
4. Guiyang Mining Investment & Development Corporation. Ltd, Guiyang 550002, China)
Abstract: More than 100 Pb-Zn deposits (spots) have been found so far in NW Guizhou province, China, and the distribution of these deposits is structurally controlled by regional structures, which is an ideal place for tracing the large-scale ore-forming fluid migration path. Base on the previous studies, this paper deeply discusses the origins of ore-forming fluids and their migration directions. The sulfide mineral samples from Tianqiao deposit have (87Sr/86Sr)200 Ma ratios ranging from 0.7118 to 0.7130 (averaging 0.7123, n=7); the (87Sr/86Sr)200 Ma ratios of sphalerite samples from Shaojiwan deposit range from 0.7113 to 0.7129 (averaging 0.7120, n=5); Qingshan sphalerite and its fluids inclusion have (87Sr/86Sr)200 Ma ratios of 0.7099 - 0.7126 (averaging 0.7111, n=8); the sphalerite samples from Shanshulin deposit have (87Sr/86Sr)200 Ma ratios ranging from 0.7107 to 0.7115 (averaging 0.7113, n=7); and the (87Sr/86Sr)200 Ma ratios of calcite and ore whole-rock from Yinchangpo deposit range from 0.7108 to 0.7255 (averaging 0.7152, n=8). It is clear that Yinchangpo deposit controlled by NE-trending structure has more radiogenic Sr than other four deposits controlled by NW-trending structure. Additionally, the radiogenic Sr is gradually declining from Tianqiao to Shanshulin. Compared with the Sr isotopic compositions of sulfide deposits with mantle of Emeishan basalts, ore-hosting sedimentary rocks and basement rocks (Kunyang/Huili Group), it is suggesting that the ore-forming fluids of Pb-Zn deposits in NW Guizhou Province have been derived from or migrated through the radiogenic Sr-enriched basement rocks. It’s indicated that the migration directions of ore-forming fluids can be divided into three groups, the metals-bearing fluids that sourced from or migrated through the radiogenic Sr-enriched basement rocks migrating from SW to NE or W to E, the metals-bearing fluids that sourced from or migrated through the radiogenic Sr-depleted ore-hosting sedimentary rocks migrating from NW to SE, and the sulfur-bearing fluids originated from ore-hosting sedimentary rocks migrating from SE to NW. Therefore, the mixed fluids mineralization occurred in the benefit structure space and precipitated sulfide minerals.
Keywords: Sr isotopes; ore-forming fluid; migration; NW Guizhou Pb-Zn metallogenic district
ACTA MINERALOGICA SINICA Vol. 35, No. 4, 2015, Page 509-514
