Vertical Alteration Zoning And Elements Distribution Of Tiegelongnan Porphyry-Epithermal Deposit,Tibet

Tiegelongnan porphyry–epithermal deposit in Tibet is the first deposit with the characteristics of high sulfur epithermal mineralization superimposed on porphyry-type mineralization discovered in the Qinghai–Tibet Plateau,which has important scientific research value and exploration significance.In this paper,four typical boreholes(ZK1604,ZK3205,ZK3220,ZK4804)that have been constructed in this mining area are selected for drilling core recording.At the same time,the system's full–hole core rock geochemical samples are collected for 49 elemental analysis tests,combined with vertical direction.The alteration zoning study identified the distribution characteristics of the elements in the various alteration zones of the ore body,explored the causes of element enrichment–loss,and summarized the exploration geochemical markers of the deposit.Through detailed drilling core logging and microscopic identification,the vertical geological characteristics of Tiegelongnan deposit are as follows: the surface is covered by volcanic rocks without alteration and mineralization,and discontinuous ancient weathering crust can be seen under the overburden.Under the overburden,it can be successively divided into three alteration zones from shallow to deep: advanced argillization zone?beresitization zone and potassium silicate zone.The shallow part(elevation: 4500~4850m)is the advanced argillization zone,where kaolinite–dickite–alunite alteration assemblages is developed.The mineralization assemblage is dominated by Cu–S systematic minerals such as pyrite–bornite–enargite–covellite–digenite.The middle part(elevation 4100~4500m)is the beresitization zone,characterized by the development of sericite–silicification alteration assemblages and etrahedrite–tennatite–pyrite–bornite–chalcopyrite mineralization assemblages.In the deep part(elevation?4100m)is the potassium silicate zone,which develops alteration assemblages such as biotite–potassium feldspar.The mineral assemblages include pyrite–chalcopyrite–porphyry–molybdenite.Geochemical characteristics of elements show that the characteristic enriched elements in the shallow advanced argillization zone are Co,As,Sb,Sn,In,Hg,Sr,S,V,Te,and the characteristic deficient elements are Be,Cs,Ta,Nb,Mn,Zn.The positive correlation between Mn and Zn can be used as the basis for dividing the advanced argillization zone.Y,Tl,Ti,U,Ba,Sc,Ga,V and other elements are enriched in the central beresitization zone,while As,Li and other elements are depleted.The abnormal enrichment of Tl and Ga and the positive correlation between Tl–Ga and Tl–Th elements can be used as the basis for dividing the beresitization zone.The enriched elements in the deep potassium silicate zone are Re,Mo,Be,Ni,Cr,Ce,W,Hf,Zr and other elements,and the deficient elements are Sr,Hg,Bi,Cs,In,Ga,V,TFe and other elements.Re and Mo elements are not only closely related to mineralization in this zone,but also to the degree of positive correlation between them,which can be used as a marker of potassium mineralization and a basis for the division of potassium silicate zone.