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

    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

    • 摘要: 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。

       

      Abstract: 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.

       

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