Apatite fission track thermochronologic constraint on Late mesozoic uplifting of the Fenghuangshan basement uplift
Li Jianhua1,2 Zhang Yueqiao1,2 Dong Shuwen3 Shi Wei1,2 Li Hailon1,2
1.Institute of Geomechanics|Chinese Academy of Geological Sciences|Beijing 100081；2.Key Laboratory of Neotectonic Movement and Geohazard|Ministry of Land and Resources|Beijing 100081；
3.Chinese Academy of Geological Sciences|Beijing 100037
8 rock samples were collected from the Fenghuangshan basement uplift zone of the northern Dabashan tectonic beltApatite fission track(AFT)dating were carried out and their timetemperature thermal modelings were performedThe results show the uplifting history can be divided into two stages since Early Cretaceous：late Early Cretaceous slow uplifting(135±5～95±5 Ma)，Late Cretaceous rapid uplifting(95±5～65±5 Ma).The biotite 40Ar/39Ar plateau age from mylonite in the Dabashan ductile shearing zone documents there was a rapid uplifting in the age of 165.7±1.9 Ma～161.2 Ma，it was related to intensive intracontinental orogenesis of the MtsDabashanThe late Early Cretaceous slow uplifting represented a period of relative stability after Late Jurassic intracontinental orogenesisThe Late Cretaceous rapid uplifting was concomitant with postorogenic extension and collapse of the Dabashan tectonic belt，featured by the development of rifted basins along the Qinling orogenic beltThis Late Mesozoic uplifting history of Fenghuangshan basement uplift can be compared with those of the adjacent basement uplift zones such as the Huangling and Hannan terrains，but differs significantly from the Wudang terrain of southern Qinling，indicating an unhomogeneous uplifting process of the Qinling orogenic belt in Late Mesozoic periodOne rock sample was collected from the foreland structural zone，its timetemperature thermal modeling result shows a similar uplifting history between the Fenghuangshan basement uplift zone and the foreland structural zone since Early Cretaceous.