Cenozoic exhumation of the North Qinling Range: Insights from apatite and zircon (U-Th)/He thermochronology

Abstract

The Cenozoic uplift of the North Qinling Range has profoundly influenced climatic and ecological patterns across northern and southern China. However, key aspects of this orogenic event, including its principal phase(s) of exhumation, total magnitude, and detailed evolutionary processes remain poorly constrained. We present a series of apatite and zircon (U-Th)/He ages from a drill core and surface relief of Zhongnan Mt., in the middle part of North Qinling Range. Comparative analysis of apatite (U-Th)/He age discrepancies between drill core and surface samples provides a perspective to figure out variation of isotherms and then helps figure out that fault activity and topographic wave length were dominant controls on isotherm geometry in the study area. The composite vertical pseudo-transect constructed from apatite and zircon (U-Th)/He ages indicates a very fast cooling period since at least ∼ 82.7 Ma and lasted to 77 Ma, followed by a relatively slow cooling stage until 49 Ma, and then a slow cooling period to 33 Ma. These three exhumation stages are widely documented in the adjacent region, with the subduction of the Pacific Plate considered the primary driving mechanism.