Chapter 3 Tectonic Framework and Phanerozoic Geologic Evolution of China

Abstract The geologic framework of China is dominated by three major Precambrian continental blocks (North China, South China, and Tarim) and their surrounding orogenic belts. The Phanerozoic tectonics of China are represented by three orogenic systems that formed via amalgamation of these blocks and subduction/accretion along most of their margins. These orogenic systems include the Early Cambrian to early Mesozoic Altaids in the north, the Early Cambrian to Cenozoic Tethysides in the south, and the Mesozoic to present Nipponides in the east. The Altaids in northern Xinjiang, Beishan, Alxa, Inner Mongolia, and northeastern China comprises a huge orogenic collage of the Central Asian orogenic belt. The Altaids formed by substantial Phanerozoic continental growth by ocean closure and terrane accretion in the Permian-Triassic until its termination by collision with the Tarim and North China blocks in the Permo-Triassic. Southward subduction of the Mongol-Okhotsk oceanic plate beneath the North China block led to widespread magmatism and deformation in the Mesozoic. The Tethysides that occupy most of the area south of the Tarim and North China blocks acted as a major bulwark against the collision of several continental blocks, including the South China block. The western Tethysides in China is occupied by the Kunlun-Altyn-Qilian and Himalaya-Tibetan orogens that record a long amalgamation history involving the evolution of the Proto-, Paleo-, and Neo-Tethys Oceans. The Tethys Ocean was finally terminated by collision between the Indian continent and the southern margin of the Eurasian continent, giving rise to the bulk of the Tibetan Plateau. The development of the eastern Tethysides in China was dominated by Triassic amalgamation between the South China and North China blocks, which gave rise to the Qinling-Dabie-Sulu orogens, and coeval collisions with microcontinental blocks such as the Indochina block in the southeastern Tibetan Plateau. The evolution of the Nipponides started in the late Paleozoic to Triassic along the eastern margin of the Chinese mainland as a result of subduction of the Paleo-Pacific Ocean. The development of the Nipponides in the Jurassic led to extension of the Altaids in northeastern China and deformation along complicated compressional and strike-slip structures in the eastern North China block. This was followed by delamination of the lower crust of the eastern half of the North China block in the Early Cretaceous. The latest development of the Nipponides in the past few million years led to formation of marginal seas and back-arc basins off coastal China, and to recent continent-arc collision in Taiwan Island. The early Paleozoic history of China was dominated by separation of the Tarim, North China, and South China blocks from Gondwanaland and their drift across the Panthalassic Ocean. The Tarim-Alxa-North China-South China backbone that formed in the Permian-Triassic played an important role in the construction of China. According to the temporal-spatial history of the Tarim-Alxa-North China-South China block and its surrounding orogens, we postulate that most of the Paleo-Asian Ocean originally belonged to, or was part of, the Paleo-Pacific (Panthalassic) Ocean. Therefore, only two major oceanic plates were responsible for the construction of the Chinese landmass in the Phanerozoic, i.e., the Pacific (Panthalassic) and the Tethys. The Pacific Ocean encompassed a major long-lived, external ocean, and the Tethys Ocean was an internal ocean within Pangea.