Plagioclase Granite Porphyry And Metallogenic Research Of Anba Mining Area In Gansu Province, Yangshan Gold Deposit

Gold resources of Yangshan gold deposit amount reaches more than 308 tons in Wenxian Country, Gansu Province. It is the first discoveried deposit of more than 300 tons of gold resource in China and even whole Asia. It belongs to para-Carlin type gold deposits.The better development of granite dikes in mining area is closely related to gold mineralization. It is one of the prospecting criteria. We discuss the characters of plagioclase granite porphyry esposed in Yangshan area from the start of geochemistry characters. According to analysis results of systematic sampling, maintrace element and rareearth elements of granite, and lithogeochemical characteristics, the paper holds that Yangshan plagioclase granite porphyry belongs to calc-alkali magma series and superperaluminous. The higher differentiation index(77.12-87.96)indicates the intense differentiation of origin magma. The partion chart of rare earth elements is right deviation, lower ∑REE(20.59-95.27×10-6), the value of LREE/HREE is 3.15-11.48. The element Eu is negative anomaly(δEu=0.65-1.20,average 0.79) and the element Ce is not abnormal(δCe=0.90-0.98, average 0.93).(La/Sr)N is 1.84-22.23. Plagioclase granite porphyry classified mainly as S-type granite. From the discrimination diagrams for the tectonic settings of granites, Yangshan granites comed from the settings of syn-collision and post collision. Ore-forming potential of ore belt granite is very large. So research work for polymetallic comprehensive utilization in mining area can be strengthened.Sulfur tracer shows that Yangshan gold deposit formation is related to magma formation closely. Plagioclase porphyry veins K-Ar age is the similar with the altered porphyry monazite electron microprobe U-Th-Pb age. So the time of the deposit formation is similar with that of the dike emplacement. Thus the tectonic setting of the gold mineralization is the same with the magmatic rocks formation. Yangshan gold deposit geological background is in orogenic belts. Regional collisional orogenic evolution and the formation of high temperature shear heat generation is the main source of the gold mineralization in this area. The distribution position of dikes also plays a role to construct distribution.