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应用LA-ICP-MS锆石U-Pb定年和锆石Hf同位素、微量元素以及锆石Ti含量温度计方法,对浙西南华夏地块基性-超基性变质岩进行了研究.由锆石U-Pb定年获得了该地区变质基底岩石的形成年龄和变质年龄.原岩形成时的岩浆结晶锆石的U-Pb年龄约为1.85Ga,εHf(t)主要集中在-7~-3,二阶段Hf模式年龄为2.9~3.4Ga,指示源区物质可能由太古代地壳物质重熔再循环所形成.变质新生锆石的U-Pb年龄为260~230Ma,Ti含量温度计显示其变质结晶温度为610~720℃,与岩相学观察到的事实一致,证明华夏地块在印支期经历了角闪岩相变质作用,为华南二叠-三叠纪期间的构造演化提供了时间约束.该变质作用可能与古太平洋板块俯冲到华南板块之下导致的地壳变形加厚有关.印支期变质事件的认识对理解华南乃至整个东南亚地区在晚古生代-早中生代的构造演化具有重要意义.
The basic-ultrabasic metamorphic rocks of the Huaxia block in southwestern Zhejiang Province were studied by LA-ICP-MS zircon U-Pb zircon dating, zircon Hf isotopes, trace elements and zircon Ti content thermometers. -Pb dating, the age and metamorphic age of the metamorphic basement rocks in this area are obtained.The U-Pb ages of magmatic zircons during the formation of protoliths are about 1.85Ga, and εHf (t) are mainly concentrated in the range of -7-3, The stage Hf model ages range from 2.9 to 3.4 Ga, indicating that the source material may be formed by the remelting of Archean crustal materials. The U-Pb ages of the metamorphic zircons range from 260 to 230 Ma, and the Ti content thermometers show that the metamorphic crystallization temperature is 610 ~ 720 ℃, consistent with the observations of petrography that the Cathaysian Block underwent Amphibolite facies metamorphism during the Indosinian, providing time constraints for the tectonic evolution during the Permian-Triassic period in South China. The metamorphism may have something to do with the thickening of the crust caused by the subduction of the Paleo-Pacific plate to the south China plate. The understanding of the Indosinian metamorphic events is of great significance in understanding the tectonic evolution of the Late Paleozoic-Early Mesozoic in southern China and the entire Southeast Asia.