Growth Of The NE-most Tibetan Plateau By The Minshan Fault-related Fold Dominated In-sequence Imbricated Thrust System:Structural And Geochronological Constraints

Tibetan Plateau,as the“Roof of the World”,has been at the center of debate about the links between earth surface uplift,crustal thickening and rock deformation,as well as the Asian monsoonal climate.Both as the growth front,the north and the eastern edges of the Tibetan Plateau behaved different uplifting and deformational modes.To fulfill this inconsistency,we choose Minshan at the northeastern Tibetan Plateau as the main research region.Minshan is characterized by high-relief topography,the NS-striking fault-related fold system,and distinctive NW-to NEstriking deformational traces.It connects the east Kunlun fault to the north and Longmenshan thrust belt to the east.However,the initiation of enhanced uplifting,the kinematics of the main structures,and its relationship with the Cenozoic growth of the northeastern Tibetan Plateau is not yet understood.In this contribution,detailed structural investigation focuses on three important faults in the Minshan,the NSstriking Minjiang and Huya faults,and the EW-striking Xueshan fault in between,as well as their related folds.The results reveal two sequences of deformation: top-to-the south D1 deformation and top-to-the east superimposed D2 deformation.Moreover,new low-temperature thermochronological data(i.e.AHe,AFT,ZHe,and ZFT)suggest two phases of cooling event in the Minshan:(1)the Late Jurassic to Late Cretaceous(~150-100 Ma)moderate cooling event pervasive in the northeast Tibetan Plateau,which builds the pre-Cenozoic proto-plateau and may represent the southward propagation of the Qinling orogenic belt;and(2)the rapid cooling during the early-mid Miocene(~20-15 Ma)mainly along the Minjiang faults,and late Miocene(~7.5-5 Ma)cooling mainly along the Huya faults,respectively.The tendency of eastward younger apparent cooling ages is consistent with eastward insequence imbricate thrusting of the Minshan fault-related fold thrust system.Thus,we propose a new tectonic model that the NE-most Tibetan Plateau has been eastward growing mainly by the Minshan fault-dominated in-sequence imbricated thrusting since ~20-15 Ma.