| 西藏帮布勒矽卡岩型铅锌矿床闪锌矿化学成分特征及其地质意义 |
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| 关键词:sphalerite electron probes chemical composition evolution of ore-forming fluid Bangbule Pb-Zn deposit Tibet |
| 基金项目:西藏自治区地质矿产勘查开发局第六地质大队“冈底斯西段帮布勒矿区成矿规律与找矿方向研究”项目(编号: 202119);自然资源部成矿作用与矿产预测重点实验室开放基金(编号: ZS2101);中国地质科学院矿产资源研究所基本科研业务费(编号: KK2017) |
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| Chemical Composition Characteristics and Geological Significance of Sphalerite in Bangbule Skarn Pb-Zn Deposit, Tibet |
| The recently discovered Bangbule deposit is located in the western part of the Gangdise– Nyainqentangula Pb-Zn-Ag polymetallic metallogenic belt, Tibet. The chemical composition of sphalerite, one of the primary ore minerals in this deposit, is of great significance because it reveals the physicochemical conditions of mineralization and evolution of ore-forming fluids. This study investigated different generations of sphalerite from the proximal and distal skarns of the Bangbule deposit using microscopic observation and electron probe microanalysis. Two generations of sphalerite (Sph-I and Sph-II) were identified by their mineral associations, microscopic characteristics, and geochemical features. Sph-I was mostly found in the proximal skarn, which is dark red and coexists with chalcopyrite, replacing magnetite and pyrrhotite. The Fe contents of the first generation are high (Fe content of some sphalerite is greater than 10 %), whereas the Zn/Fe value is typically less than 10. Sph-II can be subdivided into two types: Sph-IIa and Sph-IIb. Sph-IIa is brownish-yellow and is found in both proximal and distal skarns. This generation sphalerite is usually filled in the gap of skarn mineral grains (e g., pyroxene and garnet) and their fractures, and the Fe contents are obviously lower than that of the Sph-I. Sph-IIb is mainly developed in the distal skarn, which is light-yellow and co-exist with galena and quartz, and Fe contents are distinctly lower than those of the Sph-I and Sph-IIa. The estimation of Fe-in-Sphalerite thermometers demonstrate that the mineralization temperatures from the Sph-I (160~314 ℃) to the Sph-II (138~157 ℃) are comparable with the results of sphalerite Zn/Fe ratios. Based on the above features, it is suggested that the early ore-forming fluids in the Bangbule deposit are of high temperature and rich in Fe, Mn, Cu, etc. As the temperature of ore-forming fluid decreases gradually, the content of Fe and Mn in the fluids decreases significantly. Spatially, the temperature and oxygen fugacity of the ore-forming fluid gradually decreased during the migration from the northwest to the southeast of the deposit, indicating that there is potential to find distal Manto-type ore-bodies in the southeast direction of the deposit. |
| WANG Yong-qiang,WANG Yong,TANG Ju-xing,HE Chuan-kai,WANG Hai-yong,YAN Peng-gang,FENG Yi-peng.2023.Chemical Composition Characteristics and Geological Significance of Sphalerite in Bangbule Skarn Pb-Zn Deposit, Tibet[J].Acta Geoscientica Sinica,44(3):485-497. |
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