Metallogenic epoch and ore-forming material source of the Tongshanling Pb-Zn polymetallic deposit in southeastern Hu'nan Province:Evidence from Sm-Nd isochron age and Pb isotope

The Tongshanling Pb-Zn polymetallic deposit is located in the collage part between the southern Hu'nan-northeastern Guangxi depression in the Yangtze Block and the northern Guangdong depression in the Cathaysia Block.It is one of the representa-tive deposits in the Nanling metallogenic province.In order to determine the metallogenic epoch of the Tongshanling Pb-Zn polymetallic deposit, the authors analyzed garnets in mineralized skarn from the deposit using Sm-Nd isotopic system and obtained an isochron age of 173±3Ma which corresponds to early Yanshanian.The metal sulfides were analyzed using Pb isotope compositions and their average ratios of ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, ²⁰⁸Pb/²⁰⁴Pb are 18.602, 15.701 and 38.729, respectively, indicating that they were mainly derived from relatively uranium lead-enriched and slightly thorium lead-defected upper crust.According to analyzing the dia-gram of (²⁰⁷Pb/²⁰⁴Pb)_i-(²⁰⁶Pb/²⁰⁴Pb)_i, the hosted granodiorite seems to have been an important material source for the Tongshanling PbZn polymetallic deposit.In addition, ore-forming material probably contained mantle components hosted in the granodiorite of the Tongshanling Pb-Zn polymetallic deposit.