Geological And Geochemical Studies And Metallogenic Prospect Of The Baoxingchang Gold Deposit,Yunnan Province

The Baoxingchang district is located in the southeast section of the Sanjiang metallogenic belt. The gold and copper deposits in this district are related to the alkali-rich porphyry formed during the Himalayan epoch in the continental collision orogenic environment. In this study, the sequence of magma evolution, alteration-mineralization zoning, ore fluid evolution and ore-controlling factors related to gold deposits have been studied in detail. Based on the characteristics of fluid inclusions and isotopic geochemistry, the genesis and exploration potential of the Baoxingchang gold deposit are discussed.The Ordovician Yingfengcun Formation is the main ore-hosting strata. The major structures, including faults and folds, control the distribution of deposits. The ore-bearing magmatic rocks are mainly granite porphyry, monzonite porphyry, and lamprophyre. The wall rock alterations related to gold mineralization are mainly pyritization, arsenopyritization, silicification and kaolinization.Fluid inclusion study shows that the homogenization temperatures and salinities of fluid inclusions in different minerals are different. The homogenization temperature of fluid inclusions in early stage quartz ranges from 128oC to 239oC, with a salinity range of 6-14 wt% Na Cl eqv. The Jinchangqing ore fluid had the characteristics of low temperature and low salinity, and formed in a shallow depth.The hydrogen and oxygen isotopes suggest a magmatic origin for the ore fluids of porphyry type copper and gold deposits. The δ³⁴SV-CDT values（from-6.8‰ to +9.1‰） indicate a participation of mantle sulfur.The Baoxingchang gold deposit formed during the stage III of Himalayan orogeny. Wall rocks were altered by the fluids after the magmatic emplacement. Au and Cu united with mantle sulfur in ore fluids and precipitated, leading to the formation of gold deposit. Structures and fluids are the major ore-controlling factors. Ore-forming potential is very well in eastern Jinchangqing ore section, northeastern Baoxingchang section, periphery of the Shuangmacao section and depth of the Rentouqing section.