Source of Metallogenic Material of Lawu Zn-Cu Polymetallic Deposit in Gangdise Metallogenic Belt, Tibet: Sulfide LA-MC-ICP-MS in-situ S Isotope Constraint

Lawumedium skarn type Zn-Cu polymetallic deposit is located in the eastern section of the Middle Gangdise Pb-Zn polymetallic metallogenic belt.The deposit is dominated by Cu-Pb-Zn mineralization, accompanied by W-Sn mineralization,obviously different from the Pb-Zn-Ag deposits developed in the same region.The Zn-Cu polymetallic ore bodies are mainly produced in the skarn of the contact zone between the monzogranite and carboniferous system, and occur in the hornfels sandy slate.To find out the source of ore-forming materials, the authors carried out the in-situ S isotope analysis by LA-MC-ICP-MS.The results are as follows:in Lawu deposit, the δ³⁴S_v-CDT values in pyrite is-2.57‰~-1.17‰, averaging-1.65‰; theδ³⁴S_v-CDT values in chalcopyrite is+1.32‰~+2.74‰, averaging+1.73‰; theδ³⁴S_v-CDT values in galena is+0.84‰~+1.53‰,with an average value of+1.09‰. The in-situ S isotope distribution is relatively concentrated, the δ³⁴S_v-CDT is-2.57‰~+2.74‰,averaging +0.09‰. Comprehensive analysis shows that the composition of isotopic sulfide in Lawu Zn-Cu polymetallic ore deposit is similar to that of the lead-zinc polymetallic deposit extensively developed in this area,relating to S-type granite caused by the orogenic collision of Indiacontinent and Eurasia.Ore-forming material was a typical skarn type deposit,rather than the sedimentary exhalative deposit previous studies suggested.