滇西北羊拉铜矿床赋矿围岩的时代和物源区特征:锆石LA-MC-ICP-MS U-Pb年龄的制约  

Detrital Zircon LA-MC-ICP-MS U-Pb Age and Provenance Characteristics of Ore-hosting Rocks in Yangla Copper Deposit,Northwestern Yunnan

作　　者：杨德庭 王彦斌[1,2] 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]北京离子探针中心,北京100037

出　　处：《地质论评》2015年第3期694-707,M0002,共15页Geological Review

基　　金：国家重点基础研究发展规划(编号2009CB421001);国土资源部公益性行业科研专项(编号201011027-1C);中国地质调查局项目(编号1212011121066)的成果

摘　　要：滇西北德钦县羊拉铜矿床赋矿围岩沉积时代的确定对深入研究羊拉铜矿的矿床成因、形成时代和构造背景具有重要的地质意义。笔者等对羊拉铜矿区里农矿段赋矿围岩绿泥板岩进行了LA-MC-ICP-MS锆石U-Pb年龄测定,获得的碎屑锆石年龄范围为306～2606 Ma,主要年龄峰约为345 Ma、429 Ma、1446 Ma、1515 Ma和1829 Ma。其中约345 Ma的最年轻的主要年龄峰限定了羊拉铜矿床赋矿围岩的沉积时代为石炭纪,并非前人认为的泥盆纪。约345 Ma的岩浆事件最为强烈,对应金沙江洋盆扩张的时代,其伴随的海底火山-喷流沉积作用可能发生于石炭纪,石炭纪的海底火山喷流-沉积作用在羊拉铜矿床的形成过程中起了主导作用,而后期花岗闪长岩体对原生层状铜矿体的叠加改造主要集中于三叠纪。此外,绿泥板岩中约为1446 Ma、1515 Ma、1829 Ma和2423 Ma的古老碎屑锆石年龄峰,暗示了金沙江缝合带羊拉铜矿区变质沉积岩的沉积物源可能来源于扬子陆块。To better understand the genesis,the formation age and the tectonic setting of Yangla copper deposit,we aim to obtain the detrital zircon ages of chlorite slate（ the ore-hosting rock of KT2 ore body in Linong ore block） by LA-MC-ICP-MS U-Pb dating. The obtained U-Pb geochronological data show that the youngest age of the detrital zircon of chlorite slate is about 306 Ma,and the detrital zircons U-Pb result is mainly concentrated at345 Ma,429 Ma,1446 Ma,1515 Ma and 1829 Ma. The depositional age of chlorite slate is constrained to later than 345 Ma,suggests the protolith of chlorite slate was deposited in the Carboniferous,shouldn＇t be thought to be Devonian in age. The highest peak in the histogram of detrital zircons ages is about at 345 Ma,suggests the magmatic event is strongest,and may coincide with the seafloor spreading and initial Jinshajiang ocean basin forming. Carboniferous syn-depositional mineralization related to seabed volcanism is the main metallogenesis of Yangla copper deposit,while stratiform copper ore body are mainly effected by the superimposed reformation with the emplaced of granodiorite at Triassic. In addition,the data of detrital zircon population at 1446 Ma,1515 Ma,1829 Ma and 2423 Ma suggest that the provenance of the meta-sedimentary rock are mainly derived from the Yangtz Block materials.

关 键 词：绿泥板岩 赋矿围岩 沉积时代 锆石U-Pb年龄 羊拉铜矿 滇西北 

分 类 号：P618.41[天文地球—矿床学] P597.3[天文地球—地质学]