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

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 ore-forming materials for gold deposit.The study of fluid inclusion showed that CO2-bearing and aqueous 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-temperature,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 metallogenic age,geological and fluid characteristics.