浙江嵊州地区陈蔡岩群变质岩的锆石年代学研究:江绍结合带对华南印支期造山运动的响应

Zircon geochronology of the metamorphic rocks of Chencai Group in Shengzhou area, Zhejiang Province:The response of the Jiangshan-Shaoxing suture zone to the Indosinian orogenic event

陈蔡岩群是华夏地块西北缘的主要前寒武纪变质基底,蕴含着有关江绍结合带构造演化的丰富信息,长期为众多学者所关注。作者最近通过路线调查和地质剖面测制,将研究区"陈蔡岩群"解体为条带状黑云斜长片麻岩、侵入其中的二长花岗岩及后期基性岩脉等。黑云斜长片麻岩的锆石年龄数据可分为多组,其中以约1800 Ma、约700Ma、220 Ma三组最为集中,前者给出了片麻岩继承锆石年龄的峰值,中者给出了片麻岩原岩时代的上限,后者为变质年龄;二长花岗岩年龄为220 Ma,与前述变质年龄对应,均为印支期构造热事件,显示了江绍结合带对华南印支期造山运动的响应。

Chencai Group is the main Precambrian basement at the northwest edge of Cathaysia. Researchers have focused on the study of Chencai Group over a long period of time because of its abundant information about the evolution of Jiangshan-Shaoxing suture zone. The authors divided the Chencai Group into banded biotite plagiogneiss, monzonitic granite and mafic dikes which intruded into the plagiogneiss. The zircon ages of biotite plagiogneiss are mainly concentrated around 1800 Ma, 700 Ma and 220 Ma. The age of about 1800 Ma is the peak value of inherited zircon in gneiss. The age of about 700 Ma is the minimum formationtime of gneiss protolith, and the age of about 220 Ma is the metamorphism age of gneiss. Monzonitic granite crystallized at 220 Ma.Metamorphism and magmation resulted from the tectonothermal event during Indosinian period, which responded to the Indosinian orogeny of South China.