| 西藏铁格隆南Cu-Au矿床成矿流体特征及与矿化蚀变的内在联系 |
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| 关键词:fluid inclusion assemblages microthermometry Raman spectral Tiegelongnan porphyry-epithermal deposit Bangong–Nujiang ore belt Duolong ore concentration area |
| 基金项目:国土资源部公益性行业专项(编号: 201511017);中国地质科学院基本科研业务费项目(编号: YYWF201608) |
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| Fluid Inclusion Feature and Its Internal Relationship with Mineralization and Epithermal Alteration of the Tiegelongnan Cu-Au Deposit |
| The giant Tiegelongnan porphyry-high sulfidation epithermal Cu-Au deposit is located in the Duolong ore concentration area of the Bangong–Nujiang metallogenic belt in Tibet. To better confine the physical conditions of ore forming process, the authors used fluid inclusion assemblages to do microthermometry. In the porphyry system, fluid inclusions in the quartz-chalcopyrite vein are dominated by aqueous fluid containing 9.2 wt to 12.9 wt percent NaCl equiv at temperatures between 330℃ and 360℃. The temperatures correspond to the trapping pressures of 121~170 bars and the paleo-depth of 1.21~1.70 km. The cores were sampled at the depth of 1.03~1.07 km, and it is thus estimated that the erosion depth at the spot is about 0.18~0.67 km. Fluid inclusions in quartz phenocrysts are dominated by LVS and VL fluid inclusions and the high-salinity fluid contains 29.3~35.8 wt percent NaCl equiv at the lowest trapping temperatures between 330~350℃. In epithermal system the Qz-Aln-Py-Tn-Cv vein and quartz phenocrysts contain hypersaline inclusions as well as vapor rich inclusions, the hypersaline inclusions contain 30.7~32.4 wt and 29.3~35.8 wt percent NaCl equiv, respectively, and the lowest trapping temperatures of the two subjects both range from 310℃ to 320℃. The lowest trapping temperatures correspond to the lowest trapping pressures of 74~84 bars and the minimum paleo-depth of 0.74~0.84 km. These samples were collected at the depth of 183.8~188.1 meters and hence the minimum eroded depth should be about 0.55~0.65 km. Raman spectroscopic analysis indicates that chalcopyrite and hematite mainly exist in fluid inclusions of quartz phenocrysts in the porphyry system, which is consistent with the metallic mineral composition in the system. In addition, Raman spectroscopic analysis also implies that pyrite and covellite exist in fluid inclusions of quartz phenocrysts in the epithermal system. Besides, inclusions contained in qurartz phenocrysts cut through their hosts and generally distributed in the similar direction. Together with the fact that the homogenization temperatures of fluid inclusions in quartz phenocrysts correspond with those of the mineralized veins, the authors hold that fluid contained in quartz phenocrysts was directly related to mineralization. Meanwhile these metallic grains can be observed in both vapor rich and hypersaline inclusions, which implies that both the vapor rich and the hypersaline fluids were capable of carrying Cu. It is considered that the varieties of liquid phase, homogenization temperatures, salinities and minerals contained in fluid inclusions can represent the conditions of mineralization in porphyry and epithermal systems, and these fluids could indeed carry metallogenic elements and were responsible for the formation of the Tiegelongnan porphyry-epithermal deposit. |
| HE Wen,LIN Bin,YANG Huan-huan,FANG Xiang,SONG Ying-xin,WEI Shao-gang,HOU Lin.2017.Fluid Inclusion Feature and Its Internal Relationship with Mineralization and Epithermal Alteration of the Tiegelongnan Cu-Au Deposit[J].Acta Geoscientica Sinica,38(5):638-650. |
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