Advances in tectonic genesis of Nadanhada terrane

The Nadanhada terrain is the most typical terrain in Northeast China. It is located on the West Bank of the Wusuli River in the east of Heilongjiang Province. The division of tectonic units in Nadanhada area includes five stages: geosynclinal fold zone, Mesozoic subduction zone around the Pacific Ocean, back-arc marginal sea, orogenic belt and terrain formed by the closure of forearc basin, and so on. During the Mesozoic, the northeastern China was affected by the Mongolia-Okhotsk Ocean closure and the subduction of the Paleo-Pacific Ocean, and a large-scale tectono-magmatic activity took place. At the same time, the Nadanhada terrane drifted from low latitudes and eventually grew on the eastern side of the Jiamusi massif. Therefore, the Nadanhada terrane was formed in an oceanic environment. During the Mesozoic, it was situated on the continental margin of East Asia and formed terrigenous turbidite at the trench. At the same time, it underwent continuous subduction and local accretion, and finally formed a complete sedimentary sequence including oceanic siliceous rocks and terrigenous melanges. The direction of the tectonic line of the Nadanhada terrane changes from north to south, from NNE to NNW, and then to NW, showing an arc structure protruding westward. The direction of the present tectonic line can not represent the direction of its formation. It is the direction after the transformation of Dunmi fault left-lateral strike-slip activity and Sikhot-Alin region whole rotation.