摘要
西秦岭造山带内的甘肃阳山金矿是我国最新发现的规模最大的金矿床。矿床受 EW 韧脆性剪切带控制,赋矿围岩为泥盆系碳质碳酸盐-千枚岩-板岩和侵入其中的花岗斑岩脉。流体成矿过程包括:形成石英-绢云母-黄铁矿组合的早阶段,形成石英-黄铁矿-毒砂和石英-毒砂-黄铁矿以及石英-碳酸盐-辉锑矿-自然金组合的主成矿阶段,形成碳酸盐-石英网脉的晚阶段。早阶段流体包裹体以含 CO_2包裹体为主,CO_2含量为7.3%～21.5mol%,均一温度集中于270℃～300℃,盐度<3wt.%NaCl eqv;主阶段发育纯 CO_2包襄体、水溶液包裹体和少量含 CO_2包裹体,均一温度集中于210℃～270℃,盐度集中在<2 wt.%NaCl eqv 和3～5 wt.%NaCl eqv 两个范围;晚阶段只发育水溶液包裹体,均一温度集中在160℃～210℃,盐度<3 wt.%NaCl eqv。主阶段流体包裹体类型的多样性、相似的均一温度和流体盐度的双峰特征均指示流体沸腾现象的存在,其流体包裹体捕获温度为210℃～375℃,压力为85～222MPa;赋矿断层的阀门式活动导致主阶段流体系统交替于静岩和静水压力之间,成矿深度为8.5km 左右,成矿流体系统发育在早侏罗世大陆碰撞造山过程。矿床地质特征类似于卡林型金矿。但赋存于蚀变花岗斑岩中矿体既非造山型,也不同于卡林型,成矿流体具造山型矿床特征。因此,阳山金矿可能代表一种新的金矿类型,建议称为"阳山型金矿"。
The Yangshan gold deposit, Gansu province, is the China＇s largest gold deposit recently found in the western Qinling Orogen. It is controlled by an E-trending shear zone and hosted in the Devonian carbonaceous carbonate-phyllite-slate sequence and the granite-porphyry dikes intruding into the Devonian strata, Its hydrothermal ore-forming process includes several stages ： （ 1 ） the early stage forming quartz-sericite-pyrite assemblage; （2） the main stage forming from early to late quartz-pyrite-arsenide, quartz-arsenidepyrite and quartz-carbonate-stibnite-native gold assemblages, respectively; and （3） the late stage forming carbonate-quartz veinlets. A comprehensive study, including microthermometry and compositional analysis using laser Raman spectrometry for single fluid inclusion and quardrupole mass spectrometer for bulk fluid inclusions, shows that the early stage fluid inclusions are CO2-bearing, with CO2 contents ranging 7.3% ~ 21. 5mo1% , homogenization temperatures clustering 270℃ ~ 300℃, and the salinities lower than 3 wt. % NaCl eqv. The main stage fluid inclusions are dominated by pure CO2 , H2O-solution and minor of CO2-bearing in compositions, with homogenization temperatures clustering 210℃ ~ 270℃, and the salinities clustering in two spans of 〈 2 and 3 ~ 5 wt. % NaCl eqv. All the late stage fluid inclusions are H2O-solution with homogenization temperatures between 160℃ -210℃ and salinities lower than 3 wt. % NaCl eqv. Fluid boiling in the main stage are evidenced by the co-existence of three types of fluid inclusions with similar homogenization temperatures, and by bimodality of the salinities clustering in two spans of 〈 2 and 3 ~ 5 wt. % NaCl eqv, respectively. Fluid inclusions of main stage were trapped at temperatures of 210℃ ~ 375℃ and pressures of 85 ~ 222MPa. Fault-valve activity resulted in a fluid-system with alternating lithostatic-hydrostatic pressures at the depths of about 8.5km. The ore-forming fluid-system developed during early Jurassic continental collision orogenesis. Orebodies of the Yangshan gold deposit are geologically similar to the Carlin-type, with exception of those hosted in granite-porphyry dikes, which are not similar to the orogenic-type either. The ore-forming fluid-system of the Yangshan deposit is same to the orogenic-type. Hence the Yangshan gold deposit possibly represents a new type of gold deposits called as ＂Yangshan type＂ in this paper.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2007年第9期2144-2154,共11页
Acta Petrologica Sinica
基金
国家973项目2006CB403508课题
国家自然科学基金项目(Nos.40425006和40572065)
科学院百人计划项目和武警黄金部队科研项目
南京大学内生金属矿床成矿机制研究国家重点实验室开放研究基金
关键词
阳山金矿
阳山型金矿床
流体包裹体
成矿流体
秦岭造山带
Yangshan gold deposit, Yangshan-type gold deposit, Fluid inclusion, Ore-fluid, Qinling Orogen
