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 bas in to the north of the Tongbo-Dabie Mountains, anti elongate intermontane b asins in East Qinling, were filled by marine to terrestrial sediments, in w hich the fauna and flora communicated from North China, South China, and We st 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 Qinlin g. As the remnant basins filled, submarine fan deposition shifted to the we st 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 i n Songpan-Ganzi. and the new oceanic crust provided more spare for submarin e fans. I,ater, a Triassic subduction zone was developed along the western margin of Songpan-Ganzi. and the rising island are provided a smaller amoun t of detritus to its backarc basin in the east, which became part of Songpa n-Ganzi. During the Early and Middle Triassic, the Dabie-Sulu high mountain ranges blocked the monsoon fi om blowing to the north, and, therefore, typ ical redbeds were deposited in North China for at least 15 million years, w hereas the deposits of the same age in South China are: still shallow-marin e and littoral facies with coal measures. In the Late Triassic and Jurassic , the Dabie-Sulu mountain range was leveled to low hilly country. The monso on blew to the north very easily, and coal measures were deposited all over North China. In Songpan-Ganzi, the Triassic submarine fan deposits were fo lded and metamorphosed during latest Triassic time, and the Songpan-Ganzi f old belt was formed. The Cenozoic Himalaya and its relationship with submar ine fans in the Indian Ocean is similar to the Triassic Dabie-Sulu mountain range and its relationship with the Songpan-Ganzi submarine fans. Huge sub marine fans and ultrahigh-pressure metamorphism are consequences of contine nt-continent collision, but the involved continents should have considerabl e sizes.