An orocline in the eastern Central Asian Orogenic Belt

The Central Asian Orogenic Belt (CAOB) is the largest accretionary orogen in the world with considerable Phanerozoic juvenile crustal growth. The eastern segment of the CAOB is occupied by NE China and its adjacent areas, which locates in a triangle area surrounded by Siberian Craton to the northwest, North China Craton (NCC) to the south and Pacific oceanic plate to the east. Therefore, the NE China is a key area to study the geological evolution of multiple tectonic systems and overprinting, which has become a hot research topic. In the past five decades, especially the last two decades, there have been many detailed geological investigations carried out and a lot of new data reported in NE China. A progress has been achieved in tectonic evolution, however, there are still many open questions and arguments dealing with the tectonic models, correlation of tectonic units, amalgamation of different blocks and their tectonic affinity. In this study, we did a detailed review of the tectonic evolution of NE China and regional comparison and correlation of the different tectonic units in the eastern segment of CAOB. We re-subdivided NE China into two old blocks of Erguna block (EB) and Jiamusi block (JB) with Precambrian basement and three accretionary terranes of Xing'an accretionary terrane (XAT), Songliao accretionary terrane (SAT) and Zhangguangcai accretionary terrane (ZGCAT), which are separated from each other by the Xinlin-Xiguitu suture (XXS), Hegenshan-Heihe suture (HHS), Longfengshan suture (LFS) and Mudanjiang-Yilan suture (MYS), respectively. The ZGCAT is dominantly composed of early Paleozoic magmatic arc materials and minor late Paleozoic igneous rocks with an old Yichun mini-block, while the SAT consists dominantly of the late Paleozoic magmatic rocks with two small old blocks of the Xilinhot and Longjiang mini-blocks. According to the tectonic correlation and comparation of different tectonic units, we established a new orocline tectonic model for the eastern CAOB: 1) the XAT and ZGCAT accreted to the southern (present position) margin of Ereendavaa-Erguna-Mamyn block (EEMB) and Bureya-Jiamusi-Khanka block (BJKB) with the closure of Xinlin-Xiguitu-Heilongjiang ocean during the early Paleozoic; 2) Subsequently, the SAT accreted to the southern (present position) margin of integrated XAT-ZGCAT terrane with the closure of Hegenshan-Nenjiang-Longfengshan ocean during the late Paleozoic. These initially W-E linear shaped accretionary orogenic belts were ultimately bent southward through Paleozoic time and constituted a huge Paleozoic orocline, NE China Orocline, which collided with NCC by a scissor-like style closure of Paleo-Asian Ocean (PAO) from west to east along the Solonker-Xar Moron-Changchun-Yanji suture (SXCYS) during the late Permian-middle Triassic. The NE China Orocline, together with Tuva-Mongol Orocline and Kazakhstan Orocline in the western CAOB, constituted a huge multiple orocline tectonic system in the CAOB during the Paleozoic era. Our study will contribute to the understanding on tectonic evolutions of CAOB and the NE Asian, and suggests that the orocline should be a common tectonic model for accretionary orogeny.

Automated summary

The Central Asian Orogenic Belt (CAOB) in the eastern segment, particularly in NE China, plays a crucial role in understanding the geological evolution of multiple tectonic systems and overprinting. Through detailed geological investigations and regional comparisons, a new orocline tectonic model has been established to explain the tectonic evolution in the region. This study contributes to the understanding of the tectonic evolution in CAOB and NE Asia, suggesting that oroclines may be a common tectonic model for accretionary orogeny.