云南蒙自白牛厂多金属矿床锡石原位LA-MC-ICP-MS U-Pb年代学  

LA-MC-ICP-MS U-Pb Geochronology of Cassiterite from the Bainiuchang Polymetallic Deposit,Yunnan Province,China

作　　者：李开文[1,2] 张乾[1] 王大鹏[1] 蔡伊[1,2] 刘玉平[1] 

机构地区：[1]中国科学院地球化学研究所矿床地球化学国家重点实验室,贵州贵阳550002 [2]中国科学院大学,北京100049

出　　处：《矿物学报》2013年第2期203-209,共7页Acta Mineralogica Sinica

基　　金：矿床地球化学国家重点实验室"十二五"项目群(SKLODG-ZY125-04);国家自然科学基金(批准号:40872074);国家重点基础研究发展计划(2007CB411408)

摘　　要：云南蒙自白牛厂多金属矿床位于个旧与都龙矿床之间,由于缺少年代学数据,多种成因观点相持不下。利用锡石原位LA-MC-ICP-MS U-Pb法对采自沉积作用最为显著的白羊矿段的两个锡石样品进行年代学研究,得出238U/207Pb-206Pb/207Pb等时线年龄分别为(87.4±3.7)Ma(MSWD=9.0)和(88.4±4.3)Ma(MSWD=9.9),与薄竹山花岗岩锆石U-Pb年龄(84.1±2.6～87.83±0.39)Ma在误差范围内一致,说明锡的成矿与岩浆作用关系密切。结合南岭地区其他锡多金属矿床锡石TIMS U-Pb年代学研究,锡石U-Pb定年在锡多金属矿床直接定年中具有很大优势,而原位LA-MC-ICP-MS U-Pb法定年在该类型矿床的年代学研究中更是开辟了一条新途径。由于锡石普通铅含量较高,在校正过程中会影响数据可靠性,因此该方法需进一步完善,以满足精确定年的需要。The Bainiuchang polymetallic deposit in Yunnan Province,China,is located geographically between the Gejiu deposit and the Dulong deposit.The cause on the genesis of the deposit is controversial due to the lack of reliable chronology data.This article reports the first precise in situ LA-MC-ICP-MS U-Pb age of cassiterite from the Baiyang ore block,which performs the most obvious characteristic of sedimentary.The results show that the 238U/207Pb-206Pb/207Pb isochron ages of two cassiterite samples are（87.5±3.6） Ma（MSWD=7.8） and（87.9±3.1） Ma（MSWD=8.1）,respectively.A comparison of the U-Pb cassiterite ages with zircon U-Pb ages of（84.1±2.687.83±0.39） Ma from Bozhushan granite demonstrates that there is a close relationship between tin mineralization and magmatism.Combined with the results of TIMS U-Pb chronology from other tin-polymetallic deposits in Nanling area,there is a great advantage on direct dating of tin-polymetallic deposit with cassiterite,and it provides a new way for dating the same type deposit with the method of in situ LA-MC-ICP-MS U-Pb.With higher common lead in cassiterite,this method entails further study to meet accurate age dating.

关 键 词：锡石 原位LA-MC-ICP-MS U-PB年代学 云南 白牛厂矿床 

分 类 号：P579[天文地球—矿物学] P597[天文地球—地质学]