东秦岭商丹地区武关岩群斜长角闪片岩LA-ICP-MS锆石U-Pb年龄及其地质意义

摘要

There lacks accurate chronology information about the plagioclase-amphibole schist from the Wuguan Group of Mianyuzhui Unit in Shangdan area, East Qinling, which cause the formation age and tectonic attributes of Wuguan Group cannot to be understand.The LA-ICP-MS U-Pb dating on the zircons from the plagioclase-amphibole schist yield four age clusters of ~2.45Ga, ~1.7~2.0Ga, ~0.95Ga, ~0.85Ga.Except for the youngest one group of zircon ages, the others indicate that these zircons were inherited from the crustal materials during the ascending of basaltic magma, which were sourced from the protolith magma of plagioclase-amphibole schist and recorded the growth process of South Qinling.This result suggests that the crystal age of plagioclase-amphibole schist's protolith is ~730Ma, corresponding to the break-up of the Rodinia supercontinent in Middle-LateNeoproterozoic.%东秦岭商丹地区武关岩群鮸鱼咀斜长角闪岩单元中的斜长角闪片岩缺乏较为精确的年代学资料,制约着对武关岩群形成时代及其构造属性的认识.利用LA-ICP-MS锆石U-Pb同位素测年技术对武关岩群中斜长角闪片岩进行锆石U-Pb年龄测定,所得年龄数据显示出大致5组年龄,分别为~2.45Ga,~1.7~2.0Ga,~0.95Ga~0.85Ga,~0.71~0.74Ga,除年龄值最新的一组锆石外,其余锆石均属于斜长角闪片岩的原岩岩浆在上升过程中捕获自地壳物质的继承锆石,记录了南秦岭地区基底增长的过程.据此认为斜长角闪片岩的原岩(玄武岩)的形成时代应为~730Ma,与新元古代中晚期Rodinia超大陆的裂解有关.