摘要
大别山区是扬子和中朝大陆板块之间的碰撞造山带,由扬子大陆板块中的前陆褶冲带、俯冲盖层和俯冲基底、包含在俯冲基底中的含柯石英和金刚石的超高压变质帝、变质蛇绿混杂岩带、中朝大陆板块南缘的弧前复理石推覆体以及其北缘的反向褶冲带、北部边缘为磨拉斯的后继盆地组成。古大别海洋板块于早古生代向北俯冲时,中朝大陆板块南缘可能出现过火山弧和弧后盆地。卷入前陆褶冲带的地层以及榴辉岩的Sm/Nd同位素定时表明,两个大陆板块的强烈碰撞发生在中生代早期。
The Dabie Mountains are believed to be a collisional orogen between the Yangtze and Sino-Korean continental plates in eastern China. It is composed, from south to north, of the foreland fold-thrust belt, the subducting cover and basement of the Yangtze continental plate, the tectonic or metaophiolitic mélange belt, the fore-arc flvsch nappe, the back thrust belt and the inherited basin in which there may be a buried volcanic arc and a relic back-arc basin. Eclogites containing coesite and diamond inclusions and lenticular jadeitite were found at many outcrops in the subducing basement of the Yangtze continental plate. Sm-Nd isotopic dating of coesite- and diamondbearing eclogites gives their formation ages of 243.9±0.2 Ma, 224.0±20 Ma, and 221.20±142 Ma, with initial 143Nd/144Nd ratios of -3.4, -5.4 and -17 respectively. The fore-arc flysch was formed during the Palaeozoic as evidenced by fossil remains. The grade of metamorphism of the meta-ophiolitic mélange belt along the suture zone between the two continental plates is in general increases from south to north. An early mineral assemblage in the eclogite and related rocks is represented by some relict barroisite and crossite inclusions in garnets, and the minerals later than the coesite and diamond are plagioclase, amphibole, biotite, and sometimes also chlorite. The Yangtze continental plate must have thrust northwards under the Sino-Korean along the suture zone during the Mesozoic, following the northward subduction of an oceanic plate in Palaeozoic times. This should also have involved a complex tectonic, metamorphic process by which the subducting continental plate moved to a maximum depth of more than 120 km and then further gradually uplifted and exposed near the surface (Fig. 7).
出处
《地质学报》
EI
CAS
CSCD
北大核心
1992年第1期1-14,T001,共15页
Acta Geologica Sinica
基金
国家自然科学基金(批准号4870162)
关键词
碰撞造山带
构造
变质带
大别山
Collisional orogen, ultra-high pressure metamorphic belt, ophiolitic mélange belt, coesite, diamond.
