ACCRETION AND DISPERSION OF TERRANE STRUCTURE IN HUBEI PROVINCE

1.The characteristics of three outliers in western Hubei The Huangling terrane,dated at 1981 Ma,is an Archean-Proterozoic upper amphibolite-facies terrane,which has a superposition relationship with the Shennong terrane.The Shennong terrane,dated at 1332 Ma.is represented by a sequence of neritic sedimentary rocks,dominated by Proterozoic magnesian carbonate rocks which have been slightly metamorphosed.The Wudang terrane, dated at 1336 Ma,is a lower-upper greenschist-facies terrane consisting mainly of basic-acid volcanic-sedimentary rocks. 2.The convergence of terranes By the end of the Proterozoic,the Huangling terrane,Shennong terrane and Wudang terrane drifted and converged along the Sichuan old land,covered by Sinian and lower Archean. 3.Continental dispersion Continental dispersion resulted in the formation of fractured depressions such as the Nanyang-Xiaugfan-Dongting fractured depression.The three above- mentioned terranes were split and dispersed,causing the blocks of various sizes to move eastwards,forming the Yangpo terrane,Dagu terrane and Tong- bai terrane. 4.The contact zones and juncture zones of the terranes are composed of migmatites and late Proterozoic,Paleozoic,Mesozoic and Cenozoic sediments. The fractured depressions and faults within the terranes are closely related to seismie activity.