投稿时间：2015-07-06
修订日期：2016-03-29
网络发布日期：2016-06-30
中文摘要: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H2O-NaCl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δ13C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、40Ar/36Ar和40Ar*/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H2S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。
Abstract: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 isotopes 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), calcite-(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 δD and δ18O values of the ore-forming fluids vary from -127‰ to -110‰ and -5.3‰ to 0.7‰ at the quartz-pyrite stage, and the δD and δ18O values of altered wall rocks vary from -118‰ to -108‰ and 6.3‰ to 7.9‰. The δ13C value of calcites from calcite-(quartz)-polymetallic sulfide stage and calcite stage vary from -5.3‰ to -2.0‰ and -2.9‰ to -2.2‰, and δ18O 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 fluids of early metallogenic stage consisted dominantly of meteoric water that evolved by interaction with wall rocks. Along with the mineralization, the ore-forming fluids were transformed into the mixture of meteoric water and magmatic water, but still dominated by meteoric water. The combined effect of mixed ore-forming fluids and poor H2S fluids and sulfides precipitation might have been the main mechanism of gold precipitation in this deposit.
keywords:geochemistry fluid inclusion C-H-O-He-Ar isotopes water-rock interaction Zhengguang Au deposit Da Hinggan Mountains
文章编号：
中图分类号：P618.51
文献标志码：
基金项目:本文得到中国地质调查项目(编号:12120113093600、1212011085260)、中央公益性科研院所基本业务费项目(编号:K1314)和国家自然科学基金(编号:41302061)联合资助
引用文本：
车合伟,周振华,马星华,欧阳荷根,刘军.2016.大兴安岭北段争光金矿床成因探讨:来自流体包裹体及稳定同位素的制约[J].矿床地质,35(3):539~558CHE HeWei,ZHOU ZhenHua,MA XingHua,OUYANG HeGen,LIU Jun.2016.Tentative discussion on genesis of Zhengguang Au deposit in northern Da Hinggan Mountains: Constrained by fluid inclusions and stable isotope composition[J].Mineral Deposits35(3):539~558
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