甘肃白银厂铜多金属矿田折腰山矿床下盘脉状矿体流体包裹体特征及其意义

Characteristics and Geological Significance of Fluid Inclusions from Zheyaoshan Footwall Vein Orebody in Baiyinchang Copper Polymetallic Deposit,Gansu Province

甘肃白银厂矿田位于祁连山块状硫化物矿床成矿省东部,矿体主要赋存于早-中寒武世石英角斑岩-细碧岩组合中。本文主要对折腰山矿床下盘脉状矿体成矿流体进行研究,分析成矿流体性质及成矿流体来源,探讨其成矿机制。含矿石英中流体包裹体的岩相学和显微测温结果表明,包裹体类型主要有液体包裹体、气体包裹体、纯气体包裹体、含 CO2三相包裹体、纯 CO2包裹体。第Ⅰ阶段包裹体的均一温度为201～413℃,盐度为1.43%～13.40%；第Ⅱ阶段包裹体的均一温度为217～428℃,盐度为1.91%～11.93%（NaCl,wt）。包裹体成分研究表明,成矿流体气相成分主要为 H2O,次为 CH4和 CO2,阳离子主要为 Na＋,阴离子主要为 Cl-,说明成矿流体为 H2O-NaCl-CO2-CH4体系。该矿床下盘脉状矿体的流体为岩浆流体与加热海水的混合流体,引起矿质沉淀的机制为混合作用。

The Baiyinchang mine-field is located in the east of massive sulfide deposits metallogenic province in Qilian Mountain area.The orebody is hosted in early-middle Cambrian assemblage of baschtauite and spilite.According to the study on the metallogenic fluid characteristic from the vein orebody at the footwall of Zheyaoshan deposit,this paper discusses the metallogenic mechanism,the nature and origin of ore-forming fluid.The petrography and mi-crothermometric results of fluid inclusions in ore-bearing quartz show the inclusion types are liquid inclusion,gase-ous inclusion,pure gaseous inclusion,CO2-bearing three-phase inclusion and pure CO2 inclusion.Respectively,the homogenization temperature of the first stage inclusions is concentrated between 201 ~ 413℃ while the salinity （NaCl）is on 1 .43%~13.40%,as of the second stage inclusions is concentrated between 21 7~428℃ while the sa-linity （NaCl）is on 1 .91 %~1 1 .93%.The composition in fluid inclusions indicates that the gases in fluid inclusions are chiefly composed of H2 O,and the secondary components are CH4 ,CO2 .The cations inclusions are dominanted by Na＋ while the anions by Cl- .The ore-forming system is H2 O-NaCl-CO2-CH4 system.The ore-forming fluid from the footwall vein orebody of Zheyaoshan deposit is the mixture of magmatic fluid and the heated sea water, and the ore-forming material derives from mixing of fluids.