The Isotope Geochemistry Research Of The Zhaxikang Sb–Pb–Zn–Ag Deposit In Southern Tibet

The Zhaxikang Sb–Pb–Zn–Ag deposit is the only super-large deposit within the North Himalayan Polymetallic Metallogenic Belt to date.Although many scholars have conducted extensive research on the Zhaxikang deposit,the genesis is still controversial.The main viewpoints involve hot spring,magmatic hydrothermal fluid,MVT and SEDEX overprinted by hot spring geneses.In this article,based on the research of regional metallogenic and deposit geological characteristics,we systematically collected the previous traditional isotopic data to analyse again,and carried out the non-traditional isotopic and isotope chronology research,to provide more comprehensive and credible evidence for ore genesis.The C–O,H–O–Si,S–Pb,He–Ar and Sr isotopic data indicate that both the Pb–Zn,Sb–Ag and Sb–Hg metallogenic periods have obvious crustal genesis.The Pb–Zn metallogenic period is related to the submarine volcanism with the submarine hydrothermal deposition?metasomatism?genesis;and the Sb–Ag and Sb–Hg metallogenic period may relate to the later magmatic-hydrothermal process,which overprinted the Pb–Zn metallogenic period and leached out the ore-forming elements from wall-rock.The Fe–Zn isotopic fractionation models show that the ore-forming fluids of Pb–Zn metallogenic periods has the?⁵⁶Fe_i and?⁶⁶Zn_i of–0.5‰^–1‰and–0.28‰⁰‰,which only coincide with the seafloor hydrothermal fluid system(?⁵⁶Fe values:–1.79‰⁰.04‰;?⁶⁶Zn values:–0.28‰⁰.96‰).The sphalerite has the Cd concentrations?1183²199 ppm?,Zn/Cd ratios?248⁴21?,?^114/110Cd values?–0.51‰¹.01‰?only found in exhalative system.The U–Pb age?218±10 Ma?of zircons from Mn–Fe carbonate,Sm–Nd age of Mn–Fe carbonate?173.7±7.4 Ma?,Rb–Sr age of sphalerite?147±3.2 Ma?are just in line with the time of three extensive seafloor volcano-magmatic events during synsedimentary epoch?220¹30 Ma?in the region.The U–Pb age?62±8.2 Ma?of few young zircons from Mn–Fe carbonate,Re–Os age?47.7±7.9 Ma;43.1±2.5 Ma?are during the syn-collision epoch of India-Eurasian Plate?60⁴2Ma?,when a series of orogenic Au–Sb deposits occurred in the region.In addition,the Ar–Ar age of stage 5 sericite and ESR age of stage 5 quartz are both in accordance with the magmatic-hydrothermal metallogenic event related to the leucogranite during the post-collision orogenic epoch?25 Ma to now?.To sum up,there are three pulse of mineralization events in Zhaxikang deposit:?1?T₃–K₁:The Pb–Zn metallogenic period?Stage 1 to 2?,which generated Mn–Fe carbonate and Pb–Zn sulfides with the submarine hydrothermal deposition?metasomatism?genesis related to the submarine volcanism during synsedimentary epoch.?2?E₁–E₂:Sb–Ag metallogenic period?stage 3 to 4?,which is related to the mineralization of regional orogenic Au–Sb deposits during the syn-collision epoch,overprinted the Pb–Zn metallogenic period and generated quartz-calcite-sulfides-sulfosalt minerals.?3?N₁:Sb–Hg metallogenic period?stage 5 to 6?,which is related to magmatic-hydrothermal process during post-collision orogenic epoch and generated quartz-calcite-sulfides?Stage 5 to 6?.