秦岭造山带秦岭岩群斜长角闪岩的年代学、地球化学特征及其地质意义

Geochronology and Geochemical Characteristics of the Amphibolites from the Qinling Group of Qinling Orogenic Belt and Their Geological Implications

本文对秦岭造山带秦岭岩群的三个斜长角闪岩(变质沉积岩)样品进行了岩石学、锆石U-Pb年代学和岩石地球化学研究,限定了秦岭岩群的形成时代,讨论了秦岭岩群的构造背景及归属问题。锆石定年结果显示了971 Ma、1222 Ma和840 Ma三个最大沉积年龄。秦岭岩群是一个杂岩体,秦岭岩群至少存在中元古代(较老组成部分)和新元古代早期(较新组成部分)的岩性单元。秦岭岩群变质沉积岩的锆石年龄峰主要集中在中元古代-新元古代早期,具有与扬子块体和华北块体明显不同的锆石年代学特征,秦岭岩群在中元古代-新元古代早期为独立发展的微陆块。结合秦岭岩群的年代学特征及前人的研究结果,秦岭岩群中的变质沉积岩应沉积于弧相关的构造环境。

This paper presents a study on petrology,zircon U-Pb dating and geochemistry of three amphibolites(meta-sedimentary rock)samples from the Qinling Group,which permits to constrain their formation ages,tectonic setting and tectonic affinity.Zircon dating results show three maximum depositional ages of 971 Ma,1222 Ma and 840 Ma of this rock.The Qinling Group is considered to be a complex with units of the Mesoproterozoic(older components)and early Neoproterozoic(newer components).The age peaks of the meta-sedimentary rocks from the Qinling Group are mainly clustering at Mesoproterozoic to early Neoproterozoic,which are different from the Yangtze Block and North China Block.Research suggests that the Qinling Group formed in a microcontinent with distinct evolution during Mesoproterozoic to early Neoproterozoic.Combined with the geochronological characteristics and previous research,this study deems that the meta-sedimentary rocks in the Qinling Group deposited in a arc-related tectonic environment.