湘东锡田垄上锡多金属矿床^(40)Ar/^(39)Ar同位素定年研究  

^(40)Ar/^(39)Ar isotopic dating of the Longshang tin-polymetallic deposit, Xitian orefield, eastern Hunan

作　　者：马丽艳[1] 付建明[1] 伍式崇 徐德明[1] 杨晓君[1] 

机构地区：[1]中国地质调查局宜昌地质调查中心,湖北宜昌443003 [2]湖南省地质调查院株洲矿产地质调查所,湖南株州412007

出　　处：《中国地质》2008年第4期706-713,共8页Geology in China

基　　金：中国地质调查局地质大调查项目(1212010533307;1212010813061)资助

摘　　要：垄上锡多金属矿床是湘东锡田锡矿田中的一个大型矿床,矿体赋存在锡田复式花岗岩体与泥盆系中统棋梓桥组的接触带中。笔者以白云母为测试对象,利用40Ar/39Ar同位素定年方法,精确厘定了该矿床的形成时间。结果表明:垄上矿床2个白云母样品的40Ar/39Ar坪年龄分别为(155.6±1.3)Ma、(157.2±1.4)Ma,等时线年龄分别为(155.4±1.7)Ma(MSWD=0.74)、(156.5±1.7)Ma(MSWD=1.4),与该矿田中的荷树下锡多金属矿床的成矿年龄(150Ma)在误差范围内一致,也与锡田复式岩体早期花岗岩侵入时间(151～165Ma)吻合。因此得出以下认识:湘东锡田地区主要锡多金属矿床的成矿年龄为150～160Ma;成矿作用与区内的锡田复式花岗岩体关系密切,它们都是华南燕山早期大规模成岩成矿作用高峰期的产物。The Longshang tin-polymetallic deposit, located in the Xitian area, eastern Hunan, is a large one of the Xitian tin orefield. Its orebodies occur in the contact zones between the Xintian composite granite and carbonate rocks of the Middle Devonian Qiziqiao Formation. In this study, ^40Ar/^39Ar isotopic dating of muscovite was carried out in order to determine accurately the mineralization age of the deposit. The results show that the ^40Ar/^39Ar plateau ages of two muscovite samples from the deposit are 155.6±1.3 Ma and 157.2±1.4 Ma respectively and their isochron ages are 155.4±1.7 Ma （MSWD=0.74） and 156.5±1.7 Ma （MSWD=1.4） respectively, which agree within the error limits with mineralization age （150 Ma） of the Heshuxia tin-polymetallic deposit reported previously in the same ore field and are also in accordance with the early intrusive stage of the Xitian composite granite （151-165 Ma）. Based on these age data, this paper suggests that the mineralization age of the tin- polymetallic deposit in the Xitian ore field is 150-160 Ma and that their mineralization is closely related to the Xitian composite granite. Both are products during a peak stage of large-scale rock- and ore-forming processes in the early Yanshanian in South China.

关 键 词：地球化学 ^40Ar/^39Ar同位素定年 锡多金属矿床 垄上 湘东 

分 类 号：P597.3[天文地球—地球化学]