Study On The Characteristics Of Magmatite And Mineralization In The Pangushan Tungsten Deposit,jiangxi Province

Pangushan tungsten deposit,located in the south of Yudu Country of Jiangxi province, is an old mine undergoing hundred years of mining. It is a large scale quartz vein type tungsten and bismuth deposit in outer contact zone of granite body. Predecessors have done certain research about Geological characteristics. Based on detail geological investigation, the study is carried out by comprehensive research of petrography, mineragraphy, microprobe analysis,petrogeochemistry and stable isotope geochemistry et al. With a special emphasis on the petrologic features of the deep rock mass from the latest progress of scientific drilling(SP-NLSD-2) and combination of orebodies features and minerogenetic conditions, this paper discuss geochemical characteristics, rock types genesis, evolution process, diagenetic and metallogenetic regularity and establish the model of ore-formation of Pangushan tungsten deposit, which has an important theoretical and practical significance. The following are the main results:The deep rock mass penetrates into the overlying stratum of Sinian system. The rock types of mass are greisenized fine grained granite, potassic fine-medium grained biotite granite, medium-fine grained grained biotite granite, sericite-quartz or beresitization medium-fine grained porphyritic(phenocryst-bearing) biotite granite, fine grained albite granite and fine-medium grained biotite granite. It has at least two magma evolution series,and each zone has the relations of gradual change and transition. The granite mass belongs to high-K calc-alkaline-shoshonite series, subaluminous-peraluminous rocks, characterized by high silicon, rich potassium(except albite granite), poor calcium and magnesium and highfractionated. It is originating from crust remelting type granite potentially and featured by comagmatic evolution. It has similarities between different petrofacies in trace elements spider diagrams and rare earth chondrite standardized distribution patterns. The pluton formed in the transitional period of collision and orogeny and a continental intraplate setting, and that is compressional environment to extension environment. The major rock-forming mineralsmay indicate the magma evolution towards the direction of acid, iron-rich and poor magnesium.The mineralogy features of wolframite, coexist sulphides and quartz are of certain indicating significance. The zonation structure of wolframite reveals the fluctuation of ore-forming fluid environment. The content of FeO and MnO suggests that the ore-forming temperature is characterized by reverse zonation with a trend of changing from high to low in vertical section. The content of total rare earth elements in wolframite is concentrated, with features of enrichment of heavy rare earth elements and distinct REE fractionation, derived from same origin but different stages. Based on the isotopic equilibrium fractionation formula of chemical content of coexist sulphides, wolframite or quartz, it suggests that the ore-forming temperature of Pangushan tungsten deposit is above 300℃, belonging to high-temperature hydrothermal deposit. The variation characteristics of trace elements in quartz imply advantageous parts for enrichment of mineralization.In the Pangushan tungsten deposit, mineralization is closely related to magmatite. Sulfur isotopes suggest that the sulfur is magma-derived without other sources. The test of hydrogen and oxygen isotopes shows that its main ore-forming fluid is dominated by magma water mixed with some meteoric water. Multi-phases of structure, magmatism and hydrothermalism cause massive alteration zonation in granite, which provides a great deal of resources and heat for deposit. Under favorable structure conditions, the result is forming a large scale quartz vein type tungsten and bismuth deposit.