胶北地体侏罗纪花岗岩的成因及其构造意义

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...

Genesis of Jurassic granites in Jiaobei terrane and its tectonic implications

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-Pb 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.