湘西南落家冲钨锡矿床加里东期成岩成矿年龄的测定:对华南多旋回构造-岩浆活动与成矿作用的启示  

Sm-Nd dating of scheelite in Luojiachong W-Sn deposit,Miaoershan area,southwestern Hunan Province:Implications for polycyclic tectonic-magmatic activities and metallogenesis in South China

作　　者：杜云 田磊 郑正福 陈剑锋 张小强 王敬元 周立同 樊晖 李超 DU Yun;TIAN Lei;ZHENG Zhengfu;CHEN Jianfeng;ZHANG Xiaoqiang;WANG Jingyuan;ZHOU Litong;FAN Hui;LI Chao(Hunan Institute of Geological Survey,Changsha 410116,Hunan,China;Research Center for Petrogenesis and Mineralization of Granitoid Rocks,China Geological Survey,Wuhan 430205,Hubei,China)

机构地区：[1]湖南省地质调查所,湖南长沙410116 [2]中国地质调查局花岗岩成岩成矿地质研究中心,湖北武汉430205

出　　处：《地质通报》2022年第5期886-902,共17页Geological Bulletin of China

基　　金：中国地质调查局花岗岩成岩成矿地质研究中心开放基金课题(编号:PMGR202006);中国地质调查局项目《湖南上堡地区矿产远景调查(编号:1212011120809)》;《中国矿产地质志项目》(编号:DD20221695、DD20190379、DD20160346)。

摘　　要：落家冲钨锡矿床白钨矿中Sm、Nd含量高,Sm/Nd值小,Sm-Nd等时线年龄为401.5±9.4 Ma(2σ,MSWD=0.90),^(143)Nd/^(144)Nd初始值为0.5120214±0.0000098,表明该矿床形成于加里东晚期。白钨矿εNd(t)值为-1.91~-1.99,暗示矿床成矿物质主要来自地壳。对矿区主要赋矿花岗岩进行了锆石LA-ICP-MS定年,获得成岩年龄为423.7±2.7 Ma(2σ,MSWD=0.61),属于加里东晚期第一侵入次花岗岩,其主量元素含量及特征参数变化范围较大,源岩主要为古—中元古代基底地壳的砂屑岩和泥岩,并且可能还同化混染了部分晋宁期富Ca、Mg的岩浆岩。结合前人资料,认为苗儿山及整个华南地区发生了多旋回构造-岩浆活动与成矿作用。苗儿山岩体北段和南段的主要成岩成矿时代分别为加里东期和印支期,整体具有“北加里东、南印支”的成岩成矿格局。研究结果可为指导区内找矿工作与完善华南地区成岩成矿理论提供依据。The scheelite in the mining area has high Sm and Nd contents,low Sm/Nd ratio.Its Sm-Nd isochron age is 401.5±9.4 Ma(2σ,MSWD=0.90),and the initial ratio of^(143)Nd/^(144)Nd is 0.5120214±0.0000098,indicating that the deposit was formed in the Late Caledonian period.ScheeliteεNd(t)value is-1.91~1.99,suggesting that the ore-forming material of the deposit mainly comes from the crust.Zircon LA-ICP-MS dating of the main ore-hosting granite in the mining area shows that its petrogenetic age is 423.7±2.7 Ma(2σ,MSWD=0.61),belonging to the first intrusive episode of Late Caledonian granites.Its major element contents and characteristic parameters vary widely.Its source rocks are mainly sand clastic rocks and mudstones from the Paleo-Mesoproterozoic basement crust,and it may have assimilated and mixed some Jinningian Ca and Mg-rich magmatic rocks.Based on the results of this study and previous data,it is considered that the tectonic-magmatic activities and metallogenesis in Miaoershan area and South China are multicyclic.The dominant petrogenetic and metallogenic time of the northern and southern sections of the Miaoershan pluton are Caledonian and Indosinian respectively,showing an overall“Caledonian for north and Indosinian for south”pattern.This study aims to provide a basis for guiding the prospecting work in the area and improving the petrogenetic and metallogenic theory in South China.

关 键 词：白钨矿 SM-ND定年 加里东期 成矿作用 落家冲钨锡矿床 苗儿山岩体 湖南 地质调查工程 

分 类 号：P618.67[天文地球—矿床学] P618.44[天文地球—地质学]