【摘要】 目的探讨黄陵地区TTG片麻岩的形成时代和成因。方法采用激光剥蚀—等离子质谱(LA-ICP-MS)分析技术测定基性岩脉中锆石的U-Pb年龄。结果①辉绿岩脉中继承锆石的U-Pb和谐年龄为3 037 Ma,与TTG片麻岩中继承锆石的年龄(3 051 Ma)和斜长角闪岩的年龄(3 150Ma)基本一致,指示TTG花岗质岩浆可能源于斜长角闪岩的部分熔融,部分熔融作用可能与辉绿岩脉所代表的幔源玄武质岩浆的底侵作用有关。②辉绿岩脉中结晶锆石的U-Pb年龄为2 913 Ma,与TTG片麻岩的侵入年龄(2 947 Ma)基本相同。这不仅符合辉绿岩脉的走向与TTG片麻岩片麻理的延伸方向整体一致、局部切割的事实,也说明TTG片麻岩的侵入年龄和改造为片麻岩的年龄应为2 947~2 913 Ma。③表征黄陵地区原始古不整合面的构造运动称为"水月寺运动",同位素年龄值2 600~2 500 Ma。结论辉绿岩脉中变质锆石的U-Pb年龄为2 511 Ma,可能是与"水月寺运动"相伴随的热变质事件的反映。更多还原

【Abstract】 Aim To discuss the forming age and genesis of TTG gneiss.Methods The U-Pb isotopic dating of zircons from mafic dikes by laser ablation-ICP-MS methods.Results Some research results may be summed up as follows:(1)According to the U-Pb concordant age of 3 037 Ma on the xenocrystic zircon from mafic dikes,the U-Pb concordant age of 3 051 Ma on the xenocrystic zircon from TTG gneiss,and the whole-rock Sm-Nd isochron age of 3 150 Ma on the amphibolites in the Kongling Group,it is proposed that the TTG granitic magma was derived from amphibolite melting and may be related to the underplating of basaltic magma.(2)According to the two approximately equality ages of the U-Pb upper intercept age of 2 913 Ma on the magmatic zircon from mafic dikes and the U-Pb weighted mean age of 2 947 Ma on the magmatic zircon from TTG gneiss,it is not only an answer to that they are conformity between mafic dikes and TTG gneiss in structure,but also it is concluded that the TTG granite intruded and transformed to gneiss at 2 947~2 913 Ma simultaneously.(3)The Shuiyuesi movement occured at about 2 600~2 500 Ma to represent the ancient unconformity surface in Huangling area.Conclusion The 6 analyses were made on 6 metamorphic zricon from the mafic dikes and give a weighted mean age of 2 511 Ma,the age is interpreted to represent the age of zircon formed during the metamorphic event which may be related to Shuiyuesi movement.The Kongling group,a important part of the crystalline basememt block for the Yangtze platform,is exposed in the Northern Huangling faulted upwarping in western Hubei Province.It consists of basement gneisses,including mainly of grey gneisses(TTG),amphibolites and supracrustal rocks composed of khondalite series.The TTG geniss is the major constituent part of the Kongling metamorphic complex and is intruded by mafic dikes.For the first time,U-Pb geochronology of zircons from mafic dikes by laser ablation-ICP-MS is presented and its geological implication is discussed.更多还原