Late-Paleozoic tectonic evolution and oil-gas potentiality in northeastern China

The three important events of tectonic-magmatism developed during Paleozoic in northeastern China, with the peak ages of 500Ma、320Ma and 250Ma, respectively. The granites with age of 500Ma are distributed in all tectonic units in the area and associated with the simultaneous high grade metamorphic rocks, representing Caledonian orogeny in northeastern China. The granites with age of 320Ma are mainly distributed in the Da-Xinganling Mountains, in NE trending, with a continuous geochemical evolution from subduction to post collision. It was an important event that an united continent(Jiameng continent) formed in northeastern China and neighbors. The granites with age of 250Ma are for the most part distributed in south and east parts of northeastern China. They are originated by extension after collision of North China continent and Jiameng continent. During Late-Carboniferous to Early-Permian, the south part of the united Jiameng continent was a passive continent margin connecting southwards with Paleo-Asia Ocean,where developed a series of faulted basins filled by terrestrial volcanics and sediments in north part and marine volcanics and sediments in south part. In Middle Permian, the faulted basins subsided continuously, a large marrine basin formed in the centre-south part of the Jiameng continent, where large thick sediments of marine carbonate and mudstone formed. In Late Permian-Early Triassic, as collision of North China and Jiameng continents along E-W trending Xilamulunhe fault and paleo sea basin extincted, a terrestrial sediment basin was formed in south part of the Jiameng continent. These Late Paleozoic basins are filled with thick sediments of mudstones and for the most part covered by Mesozoic-Cenozoic basins, it is worthy to be considered as a new field for oil-gas exploration.