南秦岭中、新元古代地层划分对比新认识

NEW KNOWLEDGE ABOUT DIVISION AND CORRELATION OF THE MID AND NEO PROTEROZOIC STRATA IN THE SOUTH QINLING

在运用板块动力学模式研究晚前寒武纪地层划分对比问题的基础上，根据南秦岭构造带区域地质的实际情况，提出在中、新元古代南秦岭曾经历了晋宁期造山作用和澄江期裂解作用两次重大构造事件，它们控制了区内不同岩石建造的形成和时、空分布。据此对区域内中、新元古代地层的划分对比提出了新的认识。

The latest study on the south Qinling orogenic belt has yielded some new under standings about the division and correlation of the Mid and Neo Proterozoic strata in this region. First,basic dike swarm is widespread in the basement massif of Precambrian.The whole rock Sm Nd isochron age of the dike swarm is 782±164Ma with εNd=1 5±1 0,and 40 Ar 39 Ar age of pyroxene and homblende in it is 750±4Ma and 694 4±21Ma,respectively. It shows a feature of continental tholeiite and is derived from a slightly depleted or underpleted mantle and is a product of breakup of old continent in about 800Ma±. Second,In Wudang area,the relationship of the rift sedimentary volcanic formation of Yaolinghe Group (late Sinian, 800Ma±)and the intermediate basement rock series of Wudang Group of Middle Proterozoic is of regionally angular unconformity.On the basis of discussion on the division and correlation of Late Precambrian strata in the south Qinling by the theory of plate tectonic dynamics,the authors concluded that the South Qinling Belt has undergone two big events a mountain building movement during the Jining period and a rifting movement during the Chengjiang period in Neo Proterozoic,which had controlled the construction and space time distribution of different rock units.A new division and correlation for the Mid and Neo Proterozoic strata in the South Qinling is therefore proposed.