蒙古国满都拉探矿区地质特征及流体包裹体研究

Geologic Features and Fluid Inclusions of the Mandula Exploration Area in Mongolia

满都拉探矿区位于蒙古国南戈壁省满都拉苏木。矿区地表中元古界白云岩中出露大面积含孔雀石、蓝铜矿和辉铜矿的硅化蚀变带,含铜矿物与石英脉在空间上紧密共生,石英中的流体包裹体可能保留了原生成矿流体特征。为确定其成矿地质体和成因类型,指导后续找矿工作,本文对硅化蚀变带中的石英进行了流体包裹体研究。根据石英中包裹体的产状可将包裹体分为早晚两个阶段,早阶段富含CO2(C型)和水溶液(W型)包裹体,偶见含子矿物(S型)包裹体,流体均一温度为195~384℃,盐度为2.77%~21.37%Na Cl.eqv,反映了原生成矿流体的特征。晚阶段仅出现水溶液(W型)包裹体,流体均一温度集中在95~213℃,盐度为1.27%~12.63%Na Cl.eqv。流体由早阶段的中高温、中盐度、富CO2流体向晚阶段低温、低盐度、贫CO2流体演化。据此推测成矿流体可能为岩浆流体,流体形成深度大约在5.7 km以上。

The Mandula exploration area is located in South Gobi Mandula Sumu in the south central of Mongolia. A large area of silicified alteration belt including malachite,azurite and chalcocite is exposed in the upper Proterozoic dolomite on the surface of ore field. Cu-bearing minerals are closely associated with quartz vein in space. The fluid inclusions in the quartz may contain the characteristics of original ore-forming fluid. In order to determine the ore-forming geological body and genetic type,guide further ore-prospecting work,fluid inclusion study for Cu-bearing quartz from the silicified alteration belt was carried out. According to the occurrence,the fluid inclusions are divided into early and late stages. There are mainly two types of fluid inclusions,i. e. CO2- H2O( C- type) and Na Cl- H2O( W- type) fluid inclusions with minor daughter mineral-bearing multiphase inclusion( S- type) in the early stage. The homogeneous temperatures and salinities of these fluid inclusions vary from 195℃ to 384℃ and from 2. 77 % to 21. 37 % Na Cl equivalent,respectively,which reflect the characteristics of original ore- forming fluid. Only Na Cl- H2O( W- type) fluid inclusions are found in the late stage,with homogeneous temperatures of 95 ~ 213℃ and salinities of 1. 27 % to 12. 63 % Na Cl equivalent. The results indicate that the ore fluid evolved from medium-high temperature,medium salinity and rich CO2 in the early stage to low temperature,low salinity and poor CO2 in the late stage. It suggests that the ore fluid may be magmatic fluid and the ore-forming depth is more than 5. 7 km.