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中国东部晚中生代A型花岗岩的构造制约

王德滋 赵广涛 邱检生   

  1. 南京大学地球科学系
  • 收稿日期:1995-06-20 修回日期:1995-06-20 出版日期:1995-12-20 发布日期:1995-12-20

THE TECTONIC CONSTRAINT ON THE LATE MESOZOIC A-TYPE GRANITOIDS IN EASTERN CHINA

Wang Dezi1, Zhao Guangtao2, Qiu jiansheng1   

  1. 1. Department of Earth Sciences, Nanjing University; 2. Institute of Mineral Resources, Ocean University of Qingdao
  • Received:1995-06-20 Revised:1995-06-20 Online:1995-12-20 Published:1995-12-20

摘要: 沿中国东部出露一条晚中生代巨型A型花岗岩带。根据时、空分布特点,可将其肢解为两期五带;第一期居岩时代为135~100Ma,包括下扬子带、苏鲁带、山海关带和碾子山带;第二期成岩时代为100~70Ma,位于中国东南沿海的闽浙带。它们不仅表现出不同的岩石组合特征,而且在岩体位形态上也呈现出明显的区域性变化。研究表明:第一期A型花岗岩产于东亚具有宽广剪切活动的活动大陆边缘(160~100Ma),其形成与大陆边缘内部的剪切挤压陆-陆碰撞造山带有关,并受压剪应力背景下转换拉张的制约,岩浆定位于被拉长的P剪切拉伸桥及P、R、T三组剪切交汇的拉张塌陷处;第二期A型花岗岩产于斜向俯冲边缘(1O0~70Ma)外侧增生地体拼贴带中,其形成与库拉板块向欧亚太陆俯冲导致的弧后扩张有关,岩浆定位于地壳差异升降之陷落处,此外,拉张背景下的拉张程度可能是制约A型花岗岩形成并影响岩浆性质、侵位方式等特征的重要因素之一。

Abstract: A giant Late Mesozoic A -type granitoid zone occurred in east China can be divided into five sub-zones of two episodes. The products of the first episode (135~ 100M a) include lower Yangzi zone, Northern Jiangsu-Jiaonan zone, Shanhaiguan zone and Nianzishan zone, and those of the second one (100~ 70M a) are located at the Southeastern coast of China named Fujian-Zhejiang zone. They exhibit not only various rock assemblages but also obvious regional change in their emplacement patterns of the intrusives for the different zones and episodes. The study indicates that the A-type granitoids of the first episode were produced in the continent-continent collision transpression orogenic zone in the eastern Asia active continental margin where wide shearing tectonics was well developed (160~100M a), and emplaced in the places where the extensional jogs of P-shears and the collapse in the junction of P,T, and R shear zones were developed, which was generated by the intensive transtension in the pressure-shear stress field setting. The A-type granitoids of the second episode were produced in the collisional zone of the accretional terrane in the oblique subduction continental margin of southeast China, and related to the back-arc extension resulted from the Kula plate subducted beneath the Euroasian plate (100~70M a). The magmas emplaced in the areas of collapse which was generated by the differential uplifting and depression of the crust. Moreover, the extensional degree is possibly one of the important factor that constrained the formation of the A-type granitoids and affected the characteristics of the magma nature and emplacement.