内蒙古蓬勃山金矿床地质特征及矿床成因

Geological characteristics and ore genesis of Pengboshan gold deposit in Inner Mongolia

蓬勃山金矿床为一产于石炭系浅变质地层中的石英脉型矿床;矿脉产出主要受不同方向断裂构造控制,多分布于海西期闪长岩侵入体与围岩接触带附近。微量元素分析表明,海西期闪长岩含金性明显高于石炭系地层,表明其可能为金成矿作用提供了主要的物质来源。流体包裹体研究表明,矿区主要成矿阶段石英中发育含CO2及气液两相包裹体,前者均一温度为211℃～289℃,盐度为4.51～5.23 wt%NaCl;后者均一温度为150℃～320℃,盐度为2.1～5.1 wt%NaCl;表明成矿流体为中温低盐度NaCl--CO2--H2O体系热液,分析其成矿流体主要来源于岩浆活动。因此,蓬勃山金矿床为产出于造山带中的中温岩浆热液脉型金矿床。通过对比,其成矿时代、地质特征及流体特征与穆龙套型金矿床具有一定相似性。

The Pengboshan gold deposit is a quartz vein deposit in type in Carboniferous lower grade metamophic rocks. The gold-bearing quartz veins were controlled by the faults with different directions, and most of them were distributed in the contact zone between Hercynian diorite and Carboniferous strata. Trace element analysis revealed that the gold content in diorite was higher than that in strata rocks, indicating that diorite might provide most of the oreorming materials for gold deposit. The study of fluid inclusion showed that CO2-bearing and aque- ous two-phase fluid inclusions developed in quartz in main mineralization stages. The homogenization temperature and salinity of fluid inclusions were 211℃ - 289℃ and 4. 51- 5.23 wt% NaCl in former type and 150℃ -320℃ and 2. 1 × 5.1 wt% NaCl in later type, respectively. The results showed the ore-forming fluids as a medium-temper- ature, and low salinity NaCl-CO2-H2O solution, which mainly came from diorite magmas. Pengboshan gold deposit was a medium-temperature magma-related hydrothermal deposit produced in orogenic belt environment. The Pengboshan gold deposit is some similar to the Mulongtao type gold deposit in metallogenie age, geological and fluidcharacteristics.