| 西藏邦铺斑岩钼铜矿床岩浆-热液流体演化: 流体包裹体研究 |
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| 关键词:geochemistry fluid inclusion magmatic-hydrothermal fluid Bangpu porphyry Mo (Cu) deposit Gangdise Tibet |
| 基金项目:国家973项目(编号: 2011CB403100);中国地质调查局青藏高原专项(编号: 1212010012005) |
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| Fluid Inclusion Evidence for Magmatic-Hydrothermal Evolution in the Bangpu Porphyry Molybdenum-Copper Deposit, Tibet |
| The Bangpu Mo (Cu) deposit, located in the east section of Gangdise, Tibet, is a porphyry metallogenic system, and monzogranite and diorite (porphyrite) intrusions contributed to the mineralization. According to the vein types and crosscutting relationships, the mineralization at Bangpu can be divided into three stages: Pre-mineralization stage, main-mineralization stage and post-mineralization stage. Fluid inclusions at Bangpu can be classified into types B15, B20H, B35, B60 and B80. Ore-forming fluids evolved regularly from pre-mineralization stage to post-mineralization stage. B20H, B35, B60 and B80 inclusions dominated the pre-mineralization stage with wide range of homogenization temperatures (243–421℃), salinities are 1.4–15.4 wt% and 34.3–48.3 wt%, and densities are 0.62–1.25 g?cm-3. Typical boiling inclusion assemblages of the main-mineralization stage are characterized by the coexistence of B20H, B60 and B80 inclusions with homogenization temperatures of 240–423℃, salinities of 1.7–16.5 wt% and 32.2–47.5 wt%, and densities of 0.55–1.12 g?cm-3. In the post-mineralization stage, fluid inclusions are mainly B15 and B20H types with narrow range of homogenization temperatures (119–301℃), salinities (0.9–9.7 wt%) and densities of 0.59–0.92 g?cm-3. Trapping pressures differ from the pre-mineralization stage to the post-mineralization stage, being respectively ~120 Mpa, 34–85 Mpa and 20–58 Mpa. Using Laser Raman spectroscopic analysis, the authors identified H2O contents in liquid and CO2 amounts in vapors. With Fluid inclusions microthermometry the authors studied the revolution history of fluid inclusions and linked this history to ore formation at Bangpu, Tibet. It is likely that the exsolution of magma chambers occurred at plaeodepths of ＞5 km. Transition from lithostatic to hydrostatic pressure at paleodepths of ~2 km once caused the initiation of boiling and immiscibility, and pressure fluctuations were probably the main driving force for Mo (Cu) sulfide deposition during the main-mineralization stage. At shallower depths the oxygen fugacity of magma-derived fluid increased and caused slight Mo precipitation. |
| LUO Mao-cheng,MAO Jing-wen,WANG Li-qiang,LENG Qiu-feng,CHEN Wei.2012.Fluid Inclusion Evidence for Magmatic-Hydrothermal Evolution in the Bangpu Porphyry Molybdenum-Copper Deposit, Tibet[J].Acta Geoscientica Sinica,33(4):471-484. |
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