Study On The Tectonic Thermal Evolution History Of The Nadanhadaling And Hulin Areas In Eastern Heilongjiang

Eastern Heilongjiang province belongs to the easternmost part of the Central Asian orogenic belt,which is an important part of the continental margin of Northeast Asia.Therefore,the thermal evolution history of Mesozoic-Cenozoic is the key to understand intracontinental orogeny.Since the Paleozoic,eastern Heilongjiang province has been influenced by the Paleo-Asian Ocean and Paleo-Pacific tectonic domain,whose tectonic evolution is relatively complex,thus it has become a hot area for geologists to study.Although some low-temperature thermochronological studies have been carried out in Northeast China,the research methods mainly focus on fission track,the analysis of lower temperature apatite(U-Th)/He and higher temperature zircon(U-Th)/He are relatively weak,especially the quantitative study of cooling and exhumation process is lacking,which leads to the lack of effective constraints on the thermal evolution history of Mesozoic-Cenozoic.In this paper,apatite fission track,zircon and apatite(U-Th)/He datings are used to study the tectonothermal evolution history of granites in the Nadanhadaling and Hulin areas of Northeast China.Thermochronological data and thermal history simulation results show that there are two periods of rapid exhumation and cooling events in the Nadanhadaling area:late Early Cretaceous late Cretaceous(110?70 Ma)and Paleocene Eocene(60?40 Ma).The exhumation rates are 98?164 m/Myr^-1,38?52 m/Myr^-1,and the cooling rates are 3.42?4.81?/Myr^-1 and 1.43?1.83?/Myr^-1,respectively.Due to the influence of sedimentation,the exhumation cooling in the Hulin basin has been relatively slow since Mesozoic.It mainly experienced a continuous cooling and exhumation process since Late Cretaceous(?100-56 Ma)and Eocene(?56 Ma),with exhumation rates of 63 m/Myr^-1 and 20 m/Myr^-1and cooling rates of 2.20?/Myr^-1 and 0.70?/Myr^-1,respectively.Combined with the analysis of regional structure and stress,this paper proposes that the direct causes of rapid uplift and exhumation in the Nadanhadaling and Hulin areas in the east of Heilongjiang Province are the regional compression and the multi-stage activities of Dunhua-Mishan fault zone.The internal driving force is mainly caused by the subduction of the Paleo-Pacific plate.The first stage of cooling and exhumation was caused by the NW subduction of the Paleo-Pacific plate superimposed on the Okhotsk block and collided with the East Asian continental margin;The second stage of cooling and exhumation was caused by the retreat of the plate of the Pacific subduction,which made the East Asian continental margin in an extensional setting,resulting in a large area of exhumation in Northeast China.This study enhances the understanding of the Mesozoic Cenozoic tectonic thermal evolution history of the East Asian continental margin,and is of great significance for understanding the tectonic deformation process and mechanism of the orogenic belt within the continent.