Metallogenetic Mechanism And Ore-forming Potential Evaluation Of The Zhaxikang Antimony(Sulfur Salts) Polymetallic Deposits In Tibet

The Zhaxikang deposit is a special super-lager or large antimony(sulfur salts) deposit in North Himalaya Metallogenic Belt, butthere are many bifurcations and controversies in the genesis of this deposit, which severely hinder us to understand the genesis and metallogenetic regularity of antimony(sulfur salts) polymetallic deposit in this mineralization belt, and cause some adverse impact on determiningthe regional prospecting direction. For that reasons, after carrying out a lot of field geological works, the geological and geochemical characteristics of the Zhaxikang antimony(sulfur salts) polymetallic deposit have been studied and analyzed in-depth in this paper, through using the theories and research methods of structural geology, mineralogy, petrology, mineral deposit and geochemistry of ore deposit. And then, the mineralization-prospecting model of this deposit has been established initially by combining the geological, pygeophysical, geochemicaland remote sensingcharacteristics. All industrial ore-bodies of the Zhaxikang deposit are occurred within the nearly NS- and NE-striking faults in Lower Jurassic Ritang Formation, which are controlled by strata and tectonic. The Ritang Formation is dominated by carbon-bearing calcareous slates, providingconditions of wall rock for mineralization. The nearly NS- and NE-striking faults are important structures for transmitting and depositing ore, which control the emplacement of ore body. The wall-rock alteration is dominated by silication and Fe-Mn carbonatization. Thetypomorphic study of typical sulfide minerals has shown that, this deposit has dual characteristics of strata-boundorsedimentary-reformation types, suggesting that some part of ore-forming materials are provided by ore-bearing strata. The results of element geochemistry have shown that, As, Sb and Ag elements related with mineralization in this ore-bearing strata are enriched intensively, which have close relationship with seafloor hydrothermal activity, and are one source of ore-forming materials. In this mining area, the diabaseshows same element geochemical features with the basalts from Zhela Formation and Sangxiu Formation, as well as the late Jurassicintermediate-basic dike in Cona area, indicating that these diabase could be the products of interaction between lithosphere and mantle plume or hotspot.The isotopic compositions of S, Pb, C, H and O have shown that, the ore-forming fluids dominated by meteoric water; The ore-forming elements, such as Sb, As and Ag, were sourced from the strata of Ritang Formation, while the Pb and Zn elements might be came from crystalline basement. H isotopic compositions of fluid inclusions have shown that, this mining area has nearly uplifted to the modern altitude during mineralization time. It’s inferred that this deposit had formed in Miocene epoch after combining and analyzing the pervious studied results of ancient elevation. The research results of fluid inclusions have suggested that, the homogenization temperatures and densities have no obvious change from early mineralization stage to later ore-forming stage, but the salinities show the trend of decreased first and increased later, with total characteristics of lower salinity fluid. The boiling events took place duringthe major mineralization stage, which serves as the main reasons for the precipitation and enrichment of ore-forming materials in this deposit. After studying and analyzing the comprehensive ore-prospecting information of geology, geophysics, geochemistryand remote sensing, the results have shown that, the comprehensive ore-prospecting indicators for include NS- and NE-striking faults, Ritang Formation, gasson on exposing surface, wall-rock alteration, and geochemical or geophysical anomalies. And then, the potentiality assessment of mineral resources has been carried out for discovering the Zhaxikang-type deposit in this metallogenic belt, and 3 metallogenic prospects have been delineated, which are composed of 3 preferable ore-finding areas(M1~M3), 7 permissive ore-finding areas(L1~L7) and 6 probable ore-forming areas(N1~N6), suggesting that the broad prospects of further prospectingexist in the deep area of the Zhaxikang mining area and nearby regional metallogenic belt.