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：第一期成岩时代为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，而且在岩体侵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带的活动大陆边缘（１６０～１００Ｍａ），其形成与大陆边缘内部的剪切挤压陆一陆碰撞造山带有关，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（１０～７０Ｍａ）外侧增生地体拼贴带中，其形成与库拉板块向欧亚大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。
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(135～100Ma) include lower Yangzi zone,Northern Jiangsu-Jiaonan zone,Shanhaiguan zone and Nianzishan zone,and those of the second one(100～70Ma) 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 (160～100Ma ), 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(10070Ma). 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.
出处
《高校地质学报》
CAS
CSCD
1995年第2期13-21,共9页
Geological Journal of China Universities
关键词
A型花岗岩
构造制约
晚中生代
花岗岩
A-type granitoid, tectonic constraint, Late Mesozoic, east China
