Geochemical Characteristics And Prediction Of Concealed Ore Body Of Wunan Gold Deposit In Shanshan, Xinjiang

Wunan gold deposit is located in the active zone of northern margin of Tarimu plate, which concretely exist in the structure unit of triphibian edge in the late Paleozoic in southern Tianshan. The potential of prospecting in the area is relatively outstanding, especially Au, Cu, Fe and NaCl hold the advantage. Comparing with other types gold deposits which have been discovered in Tianshan tectonic belt, the geological characteristics of the deposit , ore-forming conditions , characteristics of mineral assemblage and geochemistry in the area are relatively different, moreover it has its own conditions of synthetical ore-controlling and prospecting such as stratum lithology and structure alteration.By making using of latter-day theories and advanced methods, and according to the geological observation outdoors and the data testing indoors, the paper investigates the geological background and ore-forming characteristics, and also discusses the deposit mechanism and genesis and summarizes regularities of ore-corming. On the other hand, through the analysis of geochemical sampling, the paper confirms the axial zoning and transverse zoning of primary haloes of Wunan gold deposit for the first time, Finally we establish the model of primary superimposed halo of this deposit.The concrete improvement and some main conclusions are as follows:1. The deposit which is distinctly controlled by layer occurs in impure carbonate rock in Gancaohu Group of Lower Carboniferous. The constructs in the area are well developed. The faults and the folds and the Yiertuogushi brittle-ductile shear zone make Au in gold-bearing layer mobilize, hydrothermal exchanged, transport, enrich and then deposit at appropriate place. Magmatism has little affect on ore-forming, but the forming of gold mine is genetically related to acidic porphyry in the space.2. The grain of gold mineral in the deposit is fine, and mainly is microgranular gold distributed by disseminated thin veins. The ore and mineral assemblage show the characteristics of low-to-moderate temperature, Besides,the ore-forming temperature, pressure and depth also reveal the epithermal feature. We discuss the ore genesis by comparing it with geological characteristics of other typical Carlin type deposits inside and outside our country.3. The characteristics of primary haloes in the surface show that the high anomaly of Au goes along with gentle anomalies of leading elements such as As,Sb,Hg and with high anomalies of trailing elements such as Bi,Cu,Mo. The results sufficiently reflect that Wunan gold deposit in the surface is subjected to strong denudation and that the gold deposit outcropped in exploration line 4 is the underside of the ore body. The axial direction of primary haloes presents relatively typical reverse zoning. The sequence from leading edge to trailing edge in turn is: Bi-Cu-Mo- Sb-Pb-Ag-Au-Hg-As-Zn. Bi,Cu and Mo are the front element assemblage, and Hg,As and Zn are divided into the trailing assemblage. The appearance of this sequence is certainly due to the strong denudation of upside of the ore body, the revelation of trailing characteristics and the front halo's overprint of blind ore body in the deep place.4. According to the change regularity of axial zoning evaluation of primary haloes, we establish the connection model about front halo, trailing halo and gold mine. The model reflects that the occurrence of the ore body is gentle dipping, that is, there is no trend of steep-dipping in the deep place. The trailing halo of upside and the front halo of underside are superimposed, as a result, the stacked primary halo shape of reappearance and side appearance comes into being.The further study of geochemical characteristics and prediction of blind ore body for this type of gold deposits can provide important geochemical information to look for and explore hidden ore body. This research is of generally instructive significance to develop the potential of Southern Tianshan tectonic belt.