Provenance of Cretaceous trench slope sediments from the Mesozoic Wandashan Orogen, NE China: Implications for determining ancient drainage systems and tectonics of the Paleo-Pacific

The Wandashan Orogen of NE China is a typical accretionary orogen related to Paleo-Pacific subduction. The Raohe Complex, as a major part of the orogen, consists of mid-Triassic to mid-Jurassic radiolarian chert and intraoceanic igneous rocks in an accretionary prism overlain by weakly sheared terrestrial-sourced clastic trench slope sediments. Sensitive high-resolution ion microprobe U-Pb dating and LA-MC-ICPMS Hf isotopic analysis of detrital zircons from the terrestrial-sourced Yongfuqiao Formation sandstone show that most zircons are Phanerozoic (90%): 140-150Ma (10%), 180-220Ma (25%), 240-270Ma (15%), 300-360Ma (15%), 391-395Ma (3%), and 450-540Ma (20%), whereas 10% are Precambrian in age. About 90% of the zircons have e<inf>Hf</inf>(t) values ranging from +11.1 to -12.8. This suggests that the major provenance of the trench slope sediments was from the adjacent eastern segment of the Central Asian Orogenic Belt and the Jiamusi Block. The age of the Yongfuqiao Formation is constrained to the earliest Cretaceous, which represents the accretion time of the mid-Triassic to mid-Jurassic oceanic complexes. When compared with the Mino Complex in Japan and the Tananao Complex in Taiwan, three different provenances are identified suggesting three ancient drainage systems which transported sediments from NE China, North China, and South China to the Paleo-Pacific subduction-accretion system

The late Paleozoic to Mesozoic evolution of the eastern margin of the Central Asian Orogenic Belt in China

© 2015 Elsevier Ltd. The north-east Central Asian Orogenic Belt (CAOB) in China records terminal closure of the Paleo-Asian Ocean in the mid- to late Permian along the Solonker-Xar Moron-Changchun suture. This marks the end of the overall northward movement of the Chinese blocks from a peri-Gondwana position toward Siberia and a switch in tectonic processes to those dominated by activity associated with the Paleo-Pacific plate to the east. Four distinct changes in tectonic regime can be recognised here in the late Paleozoic to early Mesozoic: (i) north-south compression resulted in orogenesis and gave way to post-collisional extension at ~260-250. Ma with the emplacement of A-type granites; (ii) almost coeval with this, there was an the onset of east-west extension from 250 to 225. Ma along the extreme eastern margin of the CAOB, when a seaway opened between the Songliao and Jiamusi/Khanka blocks; (iii) the onset of westerly-directed compression, associated with subduction of the Paleo-Pacific plate from ~210. Ma, resulted in re-amalgamation of the Jiamusi/Khanka block with the CAOB by ~190-180. Ma and the massive generation of Jurassic I-type granitoids throughout the region; finally (iv) a change to east-west extension from ~140. Ma onward resulted from roll-back of the Paleo-Pacific plate. This latter event was accompanied by the emplacement of S-type granitoids and the development of sedimentary basins and core complexes. It also accompanied a more widespread thinning or delamination of the lithosphere across most of north-east China during the Cretaceous