地球学报2012，Vol.33Issue(4)：485-500,16.DOI:10.3975/cagsb.2012.04.09
西藏甲玛铜多金属矿床成因研究——来自流体包裹体的证据
A Study of Fluid Inclusions and Their Constraints on the Genesis of the Jiama(Gyama) Copper Polymetallic Deposit in Tibet
摘要
Abstract
The Jiama(Gyama) copper polymetallic deposit in Tibet, which is located in the eastern part of the Gangdise porphyry copper belt, is a superlarge porphyry-skarn deposit explored in recent years. A study of fluid inclusions in typical minerals of the mineralization stage from the Jiama(Gyama) deposit through heating/freezing system TEM and Laser Raman analysis shows that the ore-forming fluid was full of volatiles. Fluid homogenization of the critical phase originated from the exsolution of fluid supercritical fluid. The fluid inclusions of the main stage were assemblages of boiling inclusions. Fluorescent effect of organic inclusions are notable. Microthermometry shows that the homogenization temperature of fluid inclusions in quartz phenocrysts from the magmatic-hydrothermal stage was 250-540℃, the salinity concentration of fluid inclusions with halite minerals was 35-61 (wt%)NaCl.eq, the salinity concentration of fluid inclusions of homogeneous phase was 3-29(wt%)NaCl.eq, the homogenization temperature in quartz vein from porphyry and hornfels after the magmatic stage was 210-410℃, the salinity concentration was 33-41 (wt%)NaCl.eq, the salinity concentration of fluid inclusions in unmixing association with them was 5-25 (wt%)NaCl.eq. Homogenization temperature of skarn minerals was 130-360℃, the salinity concentration was 3-41 (wt%)NaCl.eq. The homogenization temperatures and salinity decreased step by step from the magmatic-hydrothermal transition stage to the quartz-sulfide stage. There were abundant chalcopyrite daughter minerals in fluid inclusions from quartz phenocrysts, suggesting the enrichment of metallogenic elements at the magma crystallization and differentiation stage. The results of Laser Raman show that the gas compositions were mainly CO2, CH4 and N2 in fluid inclusions from the early mineralization stage to the main mineralization stage. The gas compositions of fluid inclusions in minerals of various stages had close succession. Ore-forming fluids had high temperature and high salinity and were enriched in CO2 and CH4. The ore-forming fluids came from magma and were subsequently mixed with atmospheric water. When the magma-hydrothermal solution rose, high temperature ore-forming fluid experienced decompression and boiling due to the sudden release of pressure. Lots of CO2 and CH4 escaped, magmatic fluid was mixed with atmospheric water, causing the deposition of metallogenic elements. The deposit was genetically related to magmatic-hydrothermal mineralization.关键词
流体包裹体/特征/矿床成因/甲玛/冈底斯成矿带/西藏Key words
fluid inclusion/ characteristic/ genesis/ Jiama(Gyama)/ Gangdese metallogenic belt/ Tibet分类
天文与地球科学引用本文复制引用
周云,唐菊兴,秦志鹏,彭惠娟..西藏甲玛铜多金属矿床成因研究——来自流体包裹体的证据[J].地球学报,2012,33(4):485-500,16.基金项目
本文由国家973项目(编号:2011CB403103)、中央公益性行业科研专项(编号:200911007-02)和青藏专项(编号:1212011085529)联合资助. （编号:2011CB403103）
