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Microfabrics, in-situ trace element and sulfur isotope compositions of pyrite from the Jinjiwo copper deposit in Chengmenshan orefield, northern Yangtze Block: Syngenetic stratabound mineralization and hydrothermal remobilization
Ore Geology Reviews ( IF 3.2 ) Pub Date : 2020-12-01 , DOI: 10.1016/j.oregeorev.2020.103830
Houfa Du , Jianping Zheng , Lianrong Tian , Hao Liang , Jinwei Guo , Yixiong Li

Abstract The Jinjiwo copper deposit is located in the Jiurui ore district of the Middle-Lower Yangtze Metallogenic Belt. The deposit has stratiform orebodies hosted by Late Carboniferous carbonate units. Pyrite is the dominant metallic mineral in the ores. Here we report on an integrated study on the microfabrics, Raman spectroscopy, in-situ LA-(MC-)ICP-MS trace element and sulfur isotope of pyrite, with a view to understand the geochemical variation, genesis of copper mineralization and ore-forming process. Textural observations suggested four types of pyrite corresponding to three metallogenic episodes: syngenetic sedimentation (PyI), metamorphism or deformation (PyII), and skarn-hydrothermal mineralization including the late skarn stage (PyIII) and hydrothermal stage (PyIV). Raman spectra of pyrite reveal subtle differences in band position and widths (FWHM) and display the increasing formation temperature of from PyI, through PyIV and PyIII, to PyII. Colloform and laminated pyrite (PyI) share similarities in behavior of pairs of elements and have low Co/Ni ratios, and the former contains the highest concentrations of Bi, Cu, Pb, Zn, Ag, Au, Mn that suggest rapid precipitation from highly saturated fluids. PyII shows high Co, Ni and As concentrations and Co/Ni ratios of 0.03 to 6.19. PyIII and PyIV have greatly varying Co/Ni ratios of 1.07 to 29 and typically low Au concentrations, suggesting a hydrothermal source. PyIII is rich in Co and Se, but is depleted in As, Cu, Pb, Zn, Ag, and Au in comparison with PyIV. There are two kinds of sulfur: one is that δ34S values are near zero, suggesting that the pyrite sulfur in the ores was derived from a mixed source in deep crust, and the other is that δ34S values are less than -39.1‰, indicating the sedimentary pyrite sulfur was originated from bacterial sulfate reduction. The combined textural and compositional data of pyrite suggest that the formation of the Jinjiwo copper deposit might have recorded the submarine exhalation sedimentation and the Mesozoic tectonic transition-deformation and hydrothermal overprint.

中文翻译:

扬子地块北部城门山矿田金鸡窝铜矿黄铁矿微结构、原位微量元素及硫同位素组成:同生层向成矿与热液再动员

摘要 金鸡窝铜矿床位于扬子中下游成矿带九瑞矿区。该矿床具有晚石炭世碳酸盐岩单元赋存的层状矿体。黄铁矿是矿石中的主要金属矿物。在这里,我们报告了对微结构、拉曼光谱、原位 LA-(MC-)ICP-MS 微量元素和黄铁矿硫同位素的综合研究,以期了解地球化学变化、铜矿化的成因和矿石-成型过程。构造观察表明四种类型的黄铁矿对应于三个成矿事件:同生沉积(PyI)、变质作用或变形(PyII)和矽卡岩-热液成矿,包括晚期矽卡岩阶段(PyIII)和热液阶段(PyIV)。黄铁矿的拉曼光谱揭示了谱带位置和宽度 (FWHM) 的细微差异,并显示了从 PyI、PyIV 和 PyIII 到 PyII 的形成温度升高。胶体和层状黄铁矿 (PyI) 在成对元素的行为上具有相似性,并且 Co/Ni 比低,前者含有最高浓度的 Bi、Cu、Pb、Zn、Ag、Au、Mn,表明从高饱和流体。PyII 显示出高 Co、Ni 和 As 浓度以及 0.03 至 6.19 的 Co/Ni 比率。PyIII 和 PyIV 的 Co/Ni 比率变化很大,为 1.07 到 29,通常金浓度很低,表明存在热液源。PyIII 富含 Co 和 Se,但与 PyIV 相比,它缺乏 As、Cu、Pb、Zn、Ag 和 Au。硫有两种:一种是δ34S值接近于零,表明矿石中的黄铁矿硫来源于地壳深部的混合来源,二是δ34S值小于-39.1‰,说明沉积的黄铁矿硫来源于细菌硫酸盐还原。黄铁矿的结构和成分组合数据表明,金鸡窝铜矿床的形成可能记录了海底呼出沉积和中生代构造过渡变形和热液叠加。
更新日期:2020-12-01
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