| The Mohe Basin is located in the northern part of the Erguna massif,and the northern part is the Mongolian-Okhotsk orogen.It is the only way for the Chinese scholars to understand the Mesozoic geology of the Mongolia-Okhotsk orogen.The Mohe Basin was mainly affected by the closure of the Mongolian Okhotsk Ocean during the Late Jurassic to Early Cretaceous.Since the Cretaceous,the Mohe Basin has been mainly affected by the subduction of the Pacific plate to Eurasia.There are large-scale uplift differences in the basin.This paper uses the comprehensive interpretation of apparent density,apparent magnetic susceptibility,magnetotelluric and seismic data,regional tectonic geomorphology analysis,apatite fission track dating and thermal history simulation to comprehensively analyze the main fault properties and basin structure in the Mohe Basin.Determine the uplift difference of the Mohe Basin since the Cretaceous.Through the comprehensive interpretation of apparent density,apparent magnetic susceptibility,magnetotelluric and seismic data,it is found that the Mohe Basin mainly develops three structural styles: shovel normal faults,slope-flat reverse faults and shovel reverse faults,and imbricates are formed under their combination.Shaped thrust nappe structure,thrust triangle structure,duplex structure combination and half graben.The extensional structures developed during the Cretaceous and later periods should have developed on the basis of thrust nappe.Since the Cretaceous,the sediment unloading area in the Mohe Basin is a rift controlled by a positive fault formed by the extension and retraction of a thrust fault or a negative topography controlled by the inversion of the reverse fault.In this paper,the fission track dating method is used to find that the apparent age of the apatite fission track shows five peaks of 42 Ma,60Ma,80 Ma,98Ma and 132 Ma.The majority age is 82.57 Ma,and the overall average track length is 9.79μm.The apparent age of the eastern part of the basin is relatively concentrated and stable,and the age of the western part of the basin changes drastically.It is inferred from the distribution of apparent age that the exhumation process in the western part of the basin is more complicated and the intensity is generally greater.Using apatite fission track thermal history simulation,it is found that there are two inflection points in the thermal history of the Mohe Basin since the Jurassic,which can be divided into three sections,the first inflection point is at 120 Ma,the second inflection point is at 23 Ma;the whole is before 120 Ma,it is the cooling uplift stage,120-23 Ma is the warming up subsidence stage,and since 23 Ma is the cooling uplift stage.Combining structural geomorphology,apatite fission track age,and thermal history simulations,it is found that there are a large number of obvious uplift differences in the Mohe Basin.During the subsidence stage,the thermal history in the Mohe Basin reflects the uplifting,exfoliation and subsidence and the interphase distribution of buried samples reveals that Mohe The basin has been an intermountain basin since the Cretaceous.Analyze the dynamic mechanism of the Mohe Basin based on the regional background,it is believed that the inflection point of the Mohe Basin cooling end of 120 Ma since the Jurassic period represents the end time of the Mongolia-Okhotsk Ocean closure.The cooling uplift of the Mohe Basin since 23 Ma is related to the strong back-arc expansion of the Japanese basin caused by the Pacific plate activity,and the rapid uplift of 10 Ma is related to the accelerated subduction of the Pacific plate. |
