青海滩间山金矿的复合金成矿作用——来自流体包裹体方面的证据  

Multiple gold mineralization in Tanjianshan gold deposit:Evidence from fluid inclusions

作　　者：张德全[1] 张慧[2] 丰成友[1] 佘宏全[1] 李进文[1] 李大新[1] 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]内蒙古自治区地质矿产勘查开发局,内蒙古呼和浩特010020

出　　处：《矿床地质》2007年第5期519-526,共8页Mineral Deposits

基　　金：国家自然科学基金面上项目(项目批准号:40372051);国家科技攻关计划(课题任务书编号:2003BA612A-07)的共同资助

摘　　要：流体包裹体研究表明,滩间山矿区的金矿体是2次热液-矿化事件的叠加产物。第一次热液-矿化作用与区域上加里东碰撞造山作用有关,形成的流体属于中低温(186～250℃)、低盐度〔w(NaCleq)1.4%～7.9%〕的H2O-CO2-CH4-NaCl体系,压力变化于(4900～1800)×105Pa之间,其主要沿NW向剪切带迁移和沉淀形成金矿化。第二次热液-矿化作用与晚古生代—早中生代碰撞造山作用密切相关,产生两种不混溶流体。第一种不混溶流体属于高温的H2O-NaCl体系,可能与岩浆侵入活动有关,第二种不混溶流体为温度274～289℃,盐度w(NaCleq)1.8%～7.9%,x(CO2)=0.19～0.27,x(H2O)=0.81～0.73,压力为(2300～1100)×105Pa的H2O-CO2-NaCl体系的流体,其沿NW向剪切带内的近NS向褶皱两翼的层间破碎带流动和沉淀,并最终导致滩间山矿床内金矿体的定位。按岩压估算,第一次热液-矿化事件发生于上地壳下部,第二次热液-矿化事件发生于浅成环境,这也进一步证实了滩间山矿床的金成矿于区域晚华力西时期的隆升造山过程中。与晚加里东碰撞造山期间相比,本区晚华力西期-印支期碰撞造山过程中的最大隆升幅度达9km左右。Petrographic observations and microthermometric data of fluid inclusions in combination with ore-forming generation and ore-forming chronology indicate that gold ore bodies in the Tanjianshan gold deposit are products of multiple gold mineralization in two hydrothermal and ore-forming events. The first hydrothermal and ore- forming event occurred during the Caledonian collision of this region, and formed fluids dominated by an intermediate tolow temperature （186--250℃, low-salinity （1.4 to 7.9 wt. 96 NaCl equivalent） H2O-CO2-CH4- NaCl system with a pressure range of 4 900-1 800 bar. They moved along the NW-trending shear zone and were responsible for the first gold mineralization in the deposit. The second hydrothermal and ore-forming event was related to the Late Paleozoic-Early Mesozoic collision of this region, and formed two kinds of immiscible fluids, i.e. , H2O-NaCl fluids and H2O-CO2-NaCl fluids; the former were probably formed by post-magmatism at temperatures of 381-449℃ and salinities of 1.6-10.8 wt% NaCl equivalent, whereas the latter were genetically produced by the evolution of the former immiscible fluids under the conditions of 274-289℃, 1.8-7.9 wt% NaCl equivalent and 2.3- 1.1 kbar. The latter immiscible fluids moved and precipitated along the interbedded faults in the limbs of NS-trending folds developed in the NW-striding shear zone, which resulted eventually in the localization of gold ore bodies in the deposit.

关 键 词：地质学 流体包裹体 滩间山金矿床 造山型金矿床 柴北缘-东昆仑地区 

分 类 号：P618.51[天文地球—矿床学]