机构地区:[1]中国地质大学地球科学与资源学院,北京100083 [2]中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室,北京100037
出 处:《矿床地质》2016年第3期539-558,共20页Mineral Deposits
基 金:中国地质调查项目(编号:12120113093600;1212011085260);中央公益性科研院所基本业务费项目(编号:K1314);国家自然科学基金(编号:41302061)联合资助
摘 要:争光浅成低温热液型金矿床位于大兴安岭成矿带北段,是多宝山矿集区内的一个重要矿床。文章通过流体包裹体和C_H_O_He_Ar同位素的系统研究,对该矿床成矿流体和矿床成因进行了深入探讨。矿床成矿作用可划分为4个主要阶段:石英_黄铁矿阶段(成矿前阶段)、石英_多金属硫化物阶段(主成矿阶段)、方解石_(石英)_多金属硫化物阶段(主成矿阶段)和方解石阶段(成矿后阶段)。流体包裹体研究表明,争光金矿床主要发育富液相流体包裹体。石英_黄铁矿阶段、方解石_(石英)_多金属硫化物阶段和方解石阶段流体包裹体的均一温度分别介于116~243℃(集中于150~170℃)、129~294℃(集中于140~160℃)和130~155℃(集中于130~150℃);w(NaCleq)分别介于0.9%~10.1%、1.2%~13.8%和2.7%~8.7%。成矿流体具有低温、低盐度、相对还原的特征,属H_2O_Na Cl体系。石英_黄铁矿阶段成矿流体的δD和δ18O分别为-127‰^-110‰和-5.9‰~0.6‰,蚀变围岩的δD值和δ18O值分别为-118‰^-108‰和6.3‰~7.9‰。方解石_(石英)_多金属硫化物阶段和方解石阶段方解石的δ^(13)C分别为-5.3‰^-2.0‰和-2.9‰^-2.2‰,δ18O分别为7.7‰~9.3‰和9.9‰~13.5‰。黄铁矿流体包裹体的~3He/~4He、^(40)Ar/^(36)Ar和^(40)Ar*/4He比值分别为1.75~3.06 Ra、683~1295和0.30~0.63。综合流体包裹体特征和稳定同位素组成,认为成矿早阶段成矿流体为大气降水与围岩发生水_岩反应后的演化水。随着成矿作用的进行,成矿流体变为大气降水与岩浆水的混合水,但仍以大气降水为主导。成矿流体与贫H_2S的流体混合和硫化物沉淀的共同作用可能是该矿床金沉淀的主要机制。The Zhengguang epithermal Au deposit, located in northern Da Hinggan Mountains metallogenic belt, is an important deposit in the Duobaoshan ore concentration area. In order to further discuss ore-forming fluids and genesis of the deposit, the authors conducted a systematic study of fluid inclusions and C-H-O-He-Ar stable iso- topes for quartz, altered wall rock, calcite and pyrite. Mineralization can be divided into four main stages: Quartz-pyrite stage (pre-metallogenic stage), quartz-polymetallic sulfide stage (main metallogenic stage), cal- cite-(quartz)-polymetallic sulfide stage (main metallogenic stage) and calcite stage (post-metallogenic stage). Only liquid-rich two-phase fluid inclusions were recognized on the basis of petrographic and microthemometric analysis. Homogenization temperatures of fluid inclusions from quartz-pyrite stage, calcite-(quartz)-polymetallic sulfide stage and calcite stage vary from 116℃ to 243℃ (mainly 150--170℃ ), 129℃ to 294℃ ( mainly 140-- 160℃ ) and 130℃ to 155℃ (mainly 130--150℃ ), respectively. And salinities w(NaCleq) vary from 0.9% to 10.1%, 1.2% to 13.8% and 2.7% to 8.7%, respectively. The ore-forming fluids are characterized by low temperature, low salinity and relative reduction, belonging to H2O-NaCl system. The 3D and 3180 values of the ore-forming fluids vary from - 127%0 to - 110%0 and -5.3% to 0.7% at the quartz-pyrite stage, and the 31) and δ^18O values of altered wall rocks vary from 118‰ to - 108‰ and 6.3‰ to 7.9%0. The δ^13C value of cal- cites from calcite-(quartz)-polymetallie sulfide stage and calcite stage vary from -5.39~00 to -2.09‰ and - 2.9‰ to - 2.2‰, and δ^18O vary from 7.7‰ to 9.3‰ and 9.9% to 13.5‰,respectively. The ^3He/^4He, ^40Ar/^36Ar and ^40Ar^*/^4He ratios of fluid inclusions extracted from pyrite exhibit the range of 1.75- 3.06 Ra, 683--1295 and 0.30--0.63, respectively. Both fluid inclusions and stable isotope compositions suggest that the ore-forming
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