Metallogenesis Of Au-Sb-Pb-Zn Mineralization In Tethys Himalaya Belt, South Tibet, China

The Mazhala Sb-Au deposit,the Zhaxikang Pb-Zn-Ag-Sb polymetallic deposit and Jisong Pb-Zn deposit have been chosen to detailed research metallogenesis of the Tethyan Himalaya.Methods of field geological investigation,detailed petrographic and mineralographic studies,fluid inclusion test,ore-forming fluid C-H-O analysis,S and Pb isotopic measurement of single minerals and Ar-Ar dating of sericite as well as summarizing former research results have been done to outline the metallogenic model of Tethyan Himalaya belt.Deposits of late collisional setting are controlled by tectonics strictly,consisting of nearly EW-striking faults with its secondary faults,facture zones,dense fissure zones,interlayer slip zones and NS-striking fault systems.Wall rocks are Mesozoic half to deep-sea clastic sediments that is full of Au?Sb?Pb?Zn?Cu?Ag?As?Hg?Mn ore-forming elements.The Mazhala Au-Sb deposit is controlled by nearly EW-striking fault fracutures and NW-striking axial plane cleavage.Minerals contain native gold,stibnite,pyrite,arsenopyrite,quartz and calcite,which can be divided into pyrite-arsenopyrite stage,quartz-stibnite stage and quartz-calcite stage.The Zhaxikang quartz-sulfide veins are controlled by NS-striking normal fault system.Minerals include ganela,sphalerite,rhidochrosite,pyrite,Pb-Sb sulfosalt minerals,stibnite,Mn-siderite,arsenopyrite,quartz and calcite.This deposit have two period-mineralization containing Early course-grained Pb-Zn sulfide veins that are overprinted by later Sb-bearing mineralization to form sulfursalts or fill open space to form quartz-stibnite veins.The Jisong veins are controlled by NE-striking faults fractures.Minerals consist of galena,sphalerite,pyrrhotite,chalcopyrite,arsenopyrite,pyrite,quartz and calcite,which can be divided into galena-arsenopyrite-pyrite stage,pyrrhotite-sphalerite-chalcopyrite-qua-rtz stage,quartz-calcite-pyrite stage and quartz stage.Fluid inclusion microthermometry shows these three deposits are low to medium temperature and salinity.The Mazhala formed at temperature of 180??~320?,concentrating at 270-300?,and salinity is 0.2-9.6%wt(NaCl eqv.);Early sulfides period of the Zhaxikang varied 200-240?,salinity changes 3-10%wt(NaCl eav.).while Sb-bearing period had temperature of 180-340? and salinity of 7-12.4%wt(NaCl eqv.).The Jisong temperature concentrated at 270-310? and salinity focused on 4-8%wt(NaCl eqv.).Fluid pressure calculation indicates ore-forming depth and pressure increased from Mazhala to Zhaxikang and Jisong.Gangue minerals H-O data suggests that fluid mixing process has taking place of three deposits.The Mazhala and Jisong are mixing of metamorphic fluid with rock formation water.And the Zhaxikang is mixing of meteoric water with rock formation water.The Mazhala is-4.1-+2.6‰,indicating igneous-source sulfur.The Zhaxikang has high positive?34Sv-CDT that is similar to sediments sulfides',indicating sedimentary-source sulfur.The Jisong is a little positive and between Mazhala and regional sediments,suggesting mixing of igneous and sedimentary sulfides sulfur.The Mazhala Pb isotope indicates sediments and magama material source.The Zhaxikang early period come from wall rock,Sb-bearing period is from metamorphosed basement and former sulfide bodies.The Jisong Pb isotope indicates former igneous rock source of materials.In all,these ores formed at 20-12Ma,belonging late collsional stage.Anatexis of deeper crust induced igneous magma in late collisional stage of Himalaya,which emplaced along the main detachment faults and tectonic weak belts of metamorphic core complex.This resulted in fluid convective circulation within crust for higher geothermometry both in north and south sides.As near the metamorphic core complex,igneous water was relatively strong to form gold deposit,where a little farther to form Sb-Au deposit,and Sb deposit formed in middle area with rock-formation fluid mixing with meterioc water.When the Sb-bearing fluid met former residual Pb-Zn sulfides,remobilization process has taken place to form Sb-Pb-Zn polymetallic deposit.At last,vein-type Pb-Zn deposit formed near main detachment faults dued to igneous water mixing with rock-formation fluid.