Geology and Isotope Geochemistry of the Yinchanggou-Qiluogou Pb-Zn Deposit, Sichuan Province, Southwest China

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• 作者：Bo LI ; Jiaxi ZHOU ; Yingshu LI ; Aibing CHEN and Ruixue WANG
• 刊名：Acta Geologica Sinica - English Edition
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：90
• 期：5
• 页码：1768-1779
• 全文大小：11210K
• ISSN：1755-6724

文摘

The Yinchanggou-Qiluogou Pb-Zn deposit, located in the western Yangtze Block, southwest China, is hosted by the Upper Sinian Dengying Formation dolostone. Ore bodies occur in the Qiluogou anticline and the NS- and NNW-trending faults. Sulfide ores mainly consist of sphalerite, pyrite, galena and calcite, with subordinate dolomite and quartz. Seventeen ore bodies have been discovered to date and they have a combined 1.0 million tons of sulfide ores with average grades of 2.27wt% Zn and 6.89wt% Pb. The δD_H2O-SMOW and δ¹⁸O_H2O-SMOW values of fluid inclusions in quartz and calcite samples range from −68.9‰ to −48.7‰ and 7.3‰ to 15.9‰, respectively, suggesting that H₂O in the hydrothermal fluids sourced from metamorphic water. Calcite samples have δ¹³C_PDB values ranging from −6.2‰ to −4.1‰ and δ¹⁸O_SMOW values ranging from 15.1‰ to 17.4‰, indicating C and O in the hydrothermal fluids likely derived from a mixed source of metamorphic fluids and the host carbonates. The δ³⁴S_CDT values of sulfide minerals range from 5.5‰ to 20.3‰, suggesting that thermal chemical reduction of sulfate minerals in evaporates were the most probable source of S in the hydrothermal fluids. The ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios of sulfide minerals fall in the range of 18.11 to 18.40, 15.66 to 15.76 and 38.25 to 38.88, respectively. The Pb isotopic data of the studied deposit plot near the upper crust Pb evolution curve and overlap with the age-corrected Proterozoic basement rocks and the Upper Sinian Dengying Formation hosting dolostone. This indicates that the Pb originated from a mixed source of the basement metamorphic rocks and the ore-hosting carbonate rocks. The ore geology and C-H-O-S-Pb isotopic data suggest that the Yinchanggou-Qiluogou deposit is an unusual carbonate-hosted, strata-bound and epigenetic deposit that derived ore-forming materials from a mixed source of the underlying Porterozoic basements and the Sinian hosting carbonates.