Geology and tectonics of the Songpan-Ganzi fold belt, southwestern China

In the Late Paleozoic, the Sine-Korean (North China) and Yangtze-Cathaysian (South China) cratons collided. The Carboniferous and Permian foreland basin to the north of the Tongbo-Dabie Mountains, anti elongate intermontane basins in East Qinling, were filled by marine to terrestrial sediments, in which the fauna and flora communicated from North China, South China, and West China. In Triassic Lime. the Dabie-Sulu Mountains became a Himalaya-type mountain range as a result of continent-continent collision anti doubling of the crust. Marked exhumation of this mountain range shed huge amounts of detritus to the west. First filled were the remnant ocean basins in Qinling. As the remnant basins filled, submarine fan deposition shifted to the west to gradually Till the Songpan-Ganzi area. Songpan-Ganai is surrounded by continents with pre-Sinian basement. The Sinian anti Paleozoic strata anti their fauna anti flora are of Yangtzean affinity. Beginning in the Permian. a mid-ocean-ridge triple junction was developed in Songpan-Ganzi. and the new oceanic crust provided more spare for submarine fans. I,ater, a Triassic subduction zone was developed along the western margin of Songpan-Ganzi. and the rising island are provided a smaller amount of detritus to its backarc basin in the east, which became part of Songpan-Ganzi. During the Early and Middle Triassic, the Dabie-Sulu high mountain ranges blocked the monsoon fi om blowing to the north, and, therefore, typical redbeds were deposited in North China for at least 15 million years, whereas the deposits of the same age in South China are: still shallow-marine and littoral facies with coal measures. In the Late Triassic and Jurassic, the Dabie-Sulu mountain range was leveled to low hilly country. The monsoon blew to the north very easily, and coal measures were deposited all over North China. In Songpan-Ganzi, the Triassic submarine fan deposits were folded and metamorphosed during latest Triassic time, and the Songpan-Ganzi fold belt was formed. The Cenozoic Himalaya and its relationship with submarine fans in the Indian Ocean is similar to the Triassic Dabie-Sulu mountain range and its relationship with the Songpan-Ganzi submarine fans. Huge submarine fans and ultrahigh-pressure metamorphism are consequences of continent-continent collision, but the involved continents should have considerable sizes.