桂北一洞锡多金属矿床LA-MC-ICP-MS锡石U-Pb测年及其地质意义  

LA-MC-ICP-MS cassiterite U-Pb dating of Yidong tin polymetallic deposit in North Guangxi and its geological significance

作　　者：冯毅[1,2] 覃小锋 王宗起[3] 马收先[3] 宫江华[3] 张诚[1,2] FENG Yi;QIN Xiaofeng;WANG Zongqi;MA Shouxian;GONG Jianghua;ZHANG Cheng(College of Earth Science,Guilin University of Technology,Guilin 541006,Guangxi,China;Guangxi Key Laboratory of Exploration for Hidden Metallic Ore Deposits,Guilin University of Technology,Guilin 541006,Guangxi,China;Institute of Mineral Resources,Chinese Amdemy of Geological Sciences,Beijing 100037,China)

机构地区：[1]桂林理工大学地球科学学院,广西桂林541006 [2]桂林理工大学广西隐伏金属矿产勘查重点实验室,广西桂林541004 [3]中国地质科学院矿产资源研究所,北京100037

出　　处：《矿产与地质》2020年第3期477-485,共9页Mineral Resources and Geology

基　　金：中国地质调查局项目“重要矿种关键问题调查与矿产地质专题填图试点”(DD20160124)资助。

摘　　要：桂北一洞锡多金属矿床位于扬子板块东南缘、江南造山带西段的宝坛地区,一般认为其成因上与平英复式岩体具有密切关系。但由于缺乏直接的成矿年龄数据,其形成年龄主要是通过平英复式岩体的成岩年龄间接确定的,因此其成矿年龄还存在较大的争议。利用锡石微区原位LA-MC-ICP-MS U-Pb测年方法,对采自一洞锡多金属矿床韧性剪切带内矿体的锡石样品进行测年分析,获得锡石的207Pb/206Pb-238U/206Pb谐和年龄为(829.0±15.0)Ma(MSWD=31),该年龄值与笔者获得的平英复式岩体中含锡元素最高的第四期次(含)电气石中细粒黑云母(二长-)碱长花岗岩(Pt3ξγT^4)的形成年龄[(831.1±7.1)Ma]在误差范围内基本一致。表明锡多金属矿的成矿物质可能主要来源于平英复式岩体的第四次岩浆作用,而后期的构造活动使锡多金属元素从源岩中运移出来,并在韧性剪切带中富集成矿。Yidong tin polymetallic deposit in North Guangxi is located at Baotan area in the southeastern margin of Yangtze plate and the western part of Jiangnan orogenic belt.It is generally considered that its genesis is closely related to Pingying compplex rock mass.However,due to the lack of ore-forming age data,its ore-forming age is mainly determined indirectly through the diagenetic age of Pingying complex rock mass,so there is still a considerable controversy over its metallogenic age.In this paper,the in-situ LA-MC-ICP-MS U-Pb dating method in cassiterite micro-area is used to carry out dating analysis on the cassiterite samples collected from the orebodies in ductile shear zone in Yidong tin polymetallic deposit.The concordant age of 207Pb/206Pb-238U/206Pb of cassiterite is(829.0±15.0)Ma(MSWD=31).Within the error range,the age value is basically consistent to the formation age[(831.1±7.1 Ma)]of middle-fine-grained biotite(monzonitic)alkali-feldspar granite of the fourth phase,bearing tourmaline(Pt3ξγT^4)with the highest tin content in Pingying complex rock mass obtained by the author.It is indicated that the tin polymetallic ore-forming materials may be mainly derived from the fourth magmatism of Pingying compplex rock mass,and the later tectonic activity causes the tin polymetallic elements to migrate out of the source rock and enrich in the ductile shear zone.

关 键 词：一洞锡多金属矿床 LA-MC-ICP-MS锡石U-Pb定年 成矿年龄 桂北 

分 类 号：P618.44[天文地球—矿床学] P597[天文地球—地质学]