ON THE PROPERTY OF THE BASEMENT FORMATION IN THE PALEOZOIC BASINS OF THE YANGTZE AREA

The basement duplex structures are widely developed in the Paleozoic basins of the Yangtze Area. The intermediate metamorphic and hypometamorphic basements in the lower structural level mainly consist of the metamorphic rocks attributed to the Archaean-Lower Proterozoic granulite-amphibolite facies and amphibolite-greenschist facies with the isotopic ages of 2500-3100 Ma and 2000-2500 Ma respectively, revealing the formation of continental core and blocks in two different stages. The epimetamorphic basements of the upper structural level are Composed of the Middle Proterozoic metamorphic rocks of low-grade greenschist facies with the isotopic ages of 1000-2000Ma. The intra-sialic orogenesis at the end of the Middle Proterozoic and the A-subduction unified the whole area as an immature pan-continent of which the northern and western developed into cratons with low stability.