Study On The Devonian Tectonic-Lithofacies Palaeogeography In Tibet And Its Adjacent Areas

This paper is mainly based on Tibet 1:250000 and 1:200000 regional geological survey. In this paper, the author comprehensively collected materials and used domestic and foreign monographs and articles as well as the basic field research, to re-determine the system of Devonian strata in Qinghai-Tibet Plateau and establish the classification system of tectonic facies and sedimentary facies. According to Sedimentology , Tectonics , Stratigraphy and paleomagnetics , the study was emphasized by combining tectonic facies and sedimentary facies analysis with plate tectonics and multi-arc basin system as the guiding theory, reflecting the strata, lithofacies and tectonic setting in Devonian, reshaping the distribution pattern of the continent and marine, space allocation relationship between Orogenic belt and Multi-arc basin in that geological time. Recovered the geographical features of Qinghai-Tibet Plateau and ancient sedimentary basins in Devonian. Composed the geographical map of Qinghai-Tibet Plateau.The study received the following understandings:Part one: We summarized and integrated the system of Devonian tectonic units system of Qinghai-Tibet Plateau into 12 macrofacies, 22 facies, merged into 5 great Combinations,3 major systems, in order to meet the requirements of the study on the Devonian Tectonic-LithofaciesPalaeogeography of Tibet and its adjacent areas.Part two: Devonian Tectonic setting of Qinghai-Tibet Plateau was summarized as a main ocean and two continental margin systems. The marine is the original Paleo-Tethys Ocean, which has subducted since Devonian. The two Continental Margin Systems were the north part of the Pan-Cathaysian continental margin and the south part of Gondwana continental margin. After orogenic collision in Early Paleozoic,most northern areas has been converted to continent. The southern boundary of Pan-Cathaysian continent is Kunlun active continental margin arc. Ocean basin, Brahmaputra integrated assemblage-zone which in the south of Gondwana continent, did not open. Himalayas and Gangdise masiff as a single entity, constitute Gondwana passive continental margin epicontinental sedimentary.