Ore-forming Regulation And Prospecting Evaluation Of The Xiaojiashan Tungsten Deposit In The Barkol District,Xinjiang

The Xiaojiashan tungsten deposit, located in Barkol region of Xinjiang, is a quartz vein type tungsten deposit. The ore geology and genesis of the Xiaojiashan Tungsten deposit are not well studied as yet, especially for ore-forming fluid research. In this study, we focus on the tungsten deposit, based on geological feature, petrography lithogeochemistry and fluid inclusion studies, aiming to provide constraints on (1) the characteristics of magmatic activity and (2) the genesis of the Xiaojiashan tungsten deposit. These studies will be of great significance in interpreting the metallogenesis of Xiaojiashan tungsten deposit.The Xiaojiashan deposit located in the southern edge of central area of the east Junggar, is one of the metallic deposit in Bogda-Harlik tectonic belt. The deposit occurs tectonically in the Harlik double anticline and the tectonic line majorly oriented E-W. The regional strata are mainly composed of First and Second lithologic section of the first Dananhu Sub Formation in Middle Devonian (D2d11, D2d12). Mining area where has quartz diorite, biotite granite, moyite and a small amount of intermediate-acid granodiorite veins. The ore bodies occur in a late Hercian granite intrusion adjacent the metamorphic crystal tuff which consists of the second lithologic section of the first Dananhu Sub Formation in Middle Devonian (D2d12).Biotite granite is the most widely distributed intrusive bodies in the Xiaojiashan tungsten deposit. The granite belongs to peraluminous A-type granite with high potassic calc-alkaline series, and all rocks show light REE enriched patterns. The trace element characters suggest that crystallization differentiation might even occur in the diagenetic process, and the magmatic origin may be connected to the enriched lithospheric mantle source. The granite belongs to post-collisional extension granite and the rocks formed in an extensional tectonic environment, and it might result from magma activity in such an extensional tectonic environment.The Xiaojiashan deposit consists of tungsten-bearing quartz veins and altered wallrocks. The veins can be classified into two groups according to their orientations, i.e., grey quartz vein and white quartz vein. Fluid inclusions in tungsten-bearing veins from the Xiaojiashan deposit are characterized by the abundance of aqueous (W-type) inclusions, on the basis of their relative phases present at room temperature, phase changes during freezing runs, and laser Raman spectroscopic measurement.The EW-trending gray quartz veins have higher vapor/liquid ratios than the SN-trending white quartz veins. Microthermometry shows that grey quartz veins have 143?354? of Th,tot, and white quartz veins have 154?312? of Th,tot.Laser Raman spectroscopy reveals that CO2 is rarely found in fluid inclusions of the tungsten-bearing quartz veins.The oxygen and hydrogen isotope values lie within the magmatic sources for the water in the tungsten-bearing quartz veins at Xiaojiashan deposit, which suggests that magmatic fluids may have a major source of the ore-forming fluids. During the ore-forming process, magmatic water had separated from magmatic intrusion and brought tungsten complex to a portion where tungsten-bearing ores could be deposited. The mixing magmatic and meteoric water occur in the late stage. Being affected by hercynian tectonic activity, tungsten granitic magma intrudes from bottom to top, W element-rich transitional fluid of magmatic hydrotherm flows upward along the fissure, inducing the silicification and sericitization on upper strata. With the temperature decrease of ore-forming fluid, containing tungsten complex decomposition, and forming the quartz vein type tungsten deposit.A detailed mineral composition, mineral paragenetic association and wall rock alteration characteristics study of Xiaojiashan tungsten deposit from the Xinjiang in northwest China has yielded the following results. The Xiaojiashan tungsten deposit is similar to the South of Jiangxi in the tectonic environment, and the metallogenic model of tungsten deposit in Xiaojiashan may be the structure of "three-storey building", and metallogenic model is established.Combined with the contour map of W and Mo content, area between W and Mo content contours of southeast mineral occurrence and western chemical mining area, a great potential of tungsten deposit in the deep and periphery of southeast mineral occurrence and western chemical mining area can be constructed.