湘东南铜山岭铅锌多金属矿床成矿时代与成矿物质来源——Sm-Nd等时线年龄和Pb同位素证据

摘要

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 Pb-Zn polymetallic deposit. In addition, ore-forming material probably contained mantle components hosted in the granodiorite of the Tongshanling Pb-Zn polymetallic deposit.%铜山岭铅锌多金属矿床位于扬子地块湘南-桂东北坳陷与华夏地块粤北坳陷的拼贴部位,是中国南岭多金属成矿区代表性矿床之一.为确定矿床成矿时代,挑选铜山岭铅锌多金属矿床中含矿矽卡岩的石榴子石进行Sm-Nd同位素定年,获得的等时线年龄为173±3Ma,指示成矿作用发生于燕山早期.对金属硫化物矿物进行了Pb同位素分析,其206Pb/204Pb、207Pb/204Pb、208Pb/204Pb平均值分别为18.602、15.701、38.729,表明成矿物质来源于相对富集铀铅、略微亏损钍铅的上地壳源区.从(207Pb/204Pb)i-(206Pb/204Pb)i铅同位素演化模式图可知,寄主花岗闪长岩是铜山岭铅锌多金属矿床的重要物质来源,且成矿物质中可能含有寄存在花岗闪长岩中的地幔组分.