胶北地体侏罗纪花岗岩的成因及其构造意义  

Genesis of Jurassic granites in Jiaobei terrane and its tectonic implications

作　　者：周珊 孟凡雪 谢士稳[2] ZHOU Shan;MENG Fan-xue;XIE Shi-wen(College of Earth Sciences and Engineering,Shandong University of Science and Technology,Qingdao 266590,China;Beijing SHRIMP Center,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037.China)

机构地区：[1]山东科技大学地球科学与工程学院,山东靑岛266590 [2]中国地质科学院地质研究所北京离子探针中心,北京100037

出　　处：《岩石矿物学杂志》2021年第5期874-896,共23页Acta Petrologica et Mineralogica

基　　金：国家自然科学基金项目(41402167,41772193,41876037);自然资源部深地动力学重点实验室自主研究课题(J1901-20-9,J1901-8);山东省重大科技创新工程项目。

摘　　要：胶北地体中生代花岗岩广泛分布,以晚侏罗世最为发育,花岗岩形成时代、成因和地球动力学背景的深入研究对认识研究区构造演化有重要意义。本文选取胶北地体东部和北部侏罗纪花岗岩进行全岩主微量元素、锆石U-Pb年龄和O同位素研究,结果表明,花岗岩样品锆石U-Pb年龄主要分布在166~156 Ma之间,代表岩体的结晶年龄。此外,含有大量3 650~3 294 Ma、2 660~2 445 Ma、770~600 Ma和245~197 Ma的继承锆石。这些花岗岩具有埃达克岩的地球化学特征[高Sr/Y和(La/Yb)N值,低Y和Yb含量]。本次报道的侏罗纪花岗岩的锆石年龄和地球化学特征与前人报道的玲珑、栾家河花岗岩一致,表明胶北不同地区侏罗纪花岗岩的形成时代和成因没有明显的区别,胶北侏罗纪花岗岩可能由加厚地壳物质部分熔融而成。不同样品的继承锆石年龄分布特征和氧同位素组成具有明显的差异,结合前人资料,认为胶北侏罗纪花岗岩源区的物质来源存在差异,部分花岗岩的源区主要为胶北古老的基底,另一部分源区主要为深俯冲的扬子板块地壳岩石。古太平洋板块或Izanagi板块的俯冲作用可能直接或间接地诱发了加厚地壳的熔融。The Mesozoic granites,especially Late Jurassic,are widely distributed in Jiaobei terrane. To further understanding the formation age,genesis and geodynamic background of these granites has great significance to the crustal evolution of study area. In this paper,the major and trace elements,zircon U-Pb ages and O isotopes of the Jurassic granites in the eastern and northern Jiaobei terrane are reported. The results show that the zircon U-Pb ages of the granites studied in this paper are mainly distributed between 166 Ma and 156 Ma,representing the crystallization age of the granites. In addition,there are a large number of inherited zircons with age peaks of 3 650 ~ 3 294 Ma,2 660 ~ 2 445 Ma,770 ~ 600 Ma and 245 ~ 197 Ma. These granites shown adakite-like geochemical characteristics. The formation ages and geochemical characteristics of Jurassic granites in this study are similar to those of Linglong and Luanjiahe Jurassic granites from western Jiaobei terrane,indicating a similar source from partial melting of thickened continental lower crust. Furthermore,based on the variation of the U-P b age and O isotope of inherited zircons from different samples,we concluded that the Jurassic granites in Jiaobei terrane have multiple sources,some of them derived from the thickened continental lower crust in Jiaobei terrane and the others from subducted Yangtze block. Then,the subduction of Paleo-Pacific or Izanagi plate might play a direct or indirect role in causing the partial melting of the thickened continental lower crust.

关 键 词：胶北地体 花岗岩 锆石氧同位素 中生代岩浆活动 

分 类 号：P588.121[天文地球—岩石学] P597[天文地球—地质学]