Mineralization Study Of Mengya'a Lead-zinc Deposit,Tibet

In this paper,Mengya'a Pb-Zn deposit on the north margin of Gangdise was the research object,and two different genetic types of ore bodies in the mining area was analyzed detailed.By exhaustive studies of deposit,the author analyzed mineralogical characteristics of skarn,geochemical character of the porphyry related to mineralization,metallogenic epoch of two types orebody,and identitfied the charater and origin,determined formation mechanism of the deposit,established the mineralization model.Mengya'a mining area have two different types of mineralization:skarn and porphyry mineralization.Skarn-type orebody(No.14 ore body)mainly layered bedded bedding produced in the limestone,the limestone strata of sandstone of the Upper Carboniferous-Lower Permain,while the porphyry-type mineralization(No.13 ore body)mainly as veins,stockwork veinlets disseminated produced in the Miocene granite porphyry body.Skarn-type ore mineralization is complex,but it has significant relationships among generations,and can be divided into skarn phase,quartz-sulfide phase and supergene oxidation phase and mineralization is mainly developed in the quartz-sulfide phase.Temperature measurement of the fluid inclusions show that mineralization phase temperature of skarn-type orebody is 220?315?,salinity is 0.88?7.59%NaCleqv and mineralization phase temperature of porphyry orebody is 275?335 ?,salinity is 4.0?5.5%NaCleqv.H-O isotopes of quartz and S-Pb isotopes of sulfide show that the fluid and material are both from magma.Meanwhile,H-O isotopes also indicate that there is a large number of atmospheric precipitation in the fluid,and may lead to the precipitation of sulfides.Ar-Ar dating of alteration muscovite in skarn shows that Mengya'a skarn-type mineralization formed in 54.6±0.4 Ma,India-Eurasia collision stage.However,the formation of porphyry-type mineralization is 13.7±0.2 Ma by zircon U-Pb dating,India-Eurasia collision stage.The research of geochemistry and isotope geochemistry shows that Miocene granite porphyry originated from crustal material,and the difference between porphyry-type mineralization in this mining area and porphyry copper deposit on Gangdise is controlled by source material.