EVOLUTION OF THE PAN-CATHAYSIAN LANDMASS GROUP AND EASTERN TETHYAN TECTONIC DOMAIN

Based on the theory of plate tectonics,the present paper separates,according to the affinity,unity and independence of the global palaeocontinents,landmasses and microland-masses,the global palaeocontinents during the whole time of the Palaeozoic into three landmass groups,i.e.the Gondwana,Laurasis and Pan-Cathaysian landmass groups,all of which are described with the emphasis on the formation and evolution of the Pan-Cathaysian landmass group.The independence and unity of the Pan-Cathaysian landmass group are manifested in:(1)the united continent consisting of the Yangtze,Cathaysia(in-cluding the Yellow Sea-East China Sea-South China Sea oldland),Sino-Korean,Qaidam, Tarim,Kunlun-North Qangtang-Qamdo-Indosinian landmasses during the latest Early Palaeozoic;(2)the independent Cathaysia flora during the middle-late Late Palaeozoic,and (3)the westward migration of the Yangtze-Cathaysia and Sino-Korean landmasses as the bulk of the Pan-Cathaysian landmass group,resulting in the simultaneous obliteration of the Palaeo-Tethyan Ocean on the northern and southern sides of the landmass group,and the final formation of the global Pangea during the latest Late Palaeozoic and Early Meso-zoic.Four stages are recognized for the formation and evolution of the Pan-Cathaysian landmass group;(l)The divergence stage of all the global landmasses at the end of the Late Precambrian to Early Palaeozoic;(2)the partly Convergence stage of the landmasses and the formation of the initial Pan-Cathaysian landmass group during the latest Early Palaeozoic;(3)the divergence and rifting stage of the southwestern margin of the Pan-Cathaysian landmass group during the Late Palaeozoic,and (4)the collision and conver-gence of the Pan-Cathaysian landmass group with the Laurasis landmass group during the latest Late Palaeozoic to Early Mesozoic.In the eastern Tethyan tectonic domain,the Palaeo-Tethys not only has inherited the features of the Proto-Tethys,but also possesses the newly emerging features.The Mid-Tethys marks the beginning of a new tectonic cycle in the divergence-convergence megacycle of the Pangea rather than the continuation and development of the Palaeo-Tethys.This paper deals finally with the geodynamic mecha-nisms for the divergence and convergence of various landmasses,and reorganization and disintegration of the Pangea.In other words,the internal material of the earth migrated to-ward the southern semisphere,giving rise to the expansion of the southern semisphere and disintegration of the Pangea.The southward migration of the internal material of the earth also caused the northward movement of the material in the asthenosphere,leading to the northward movement of the microlandmasses.In addition to the vertical circulation and convection,the horizontal eddy motion of varying sizes also occurred in the creeping as-thenosphere,resulting in the rotation,convergence (the formation of the Pangea) and rapid divergence (the disintegration of the Pangea) of the landmasses.