Exhumation of the Dahinggan Mountains, NE China from the Late Mesozoic to the Cenozoic: New evidence from fission-track thermochronology

Abstract

Zircon and apatite fission-track (FT) analyses were used to reveal the exhumation of Phanerozoic granitoid intrusions in the Dahinggan Mountains, northeastern China. Zircon FT ages ranging from 84 ± 5 to 97 ± 8 Ma, and apatite FT ages from 47 ± 3 to 67 ± 4 Ma with mean track lengths between 12.3 ± 2.3 and 13.3 ± 2.2 μm, respectively, were obtained for the Phanerozoic granitoids sampled along a south–south-west to north–north-east transect across the Dahinggan Mountains. Three cooling stages from the Late Mesozoic to the Cenozoic have been identified in the studied region based on FT results and modeling. Stage one was a rapid cooling period from the closure temperature of zircon FT to the high temperature part of the apatite FT partial annealing zone (∼210–110 °C) during ∼90–57 Ma. Stage two was a relatively slow cooling period (∼110–60 °C) occurred between ∼57 Ma and 20 Ma, suggesting that the granitoids had been exhumed to depths of ∼1–2 km. The final stage was a cooling period (60–20 °C) occurred since the Miocene, which bring studied samples to the Earth’s surface at an accelerated exhumation rate. The estimated maximum exhumation is ∼5 km assuming a steady-state geothermal gradient of 35 °C/km. Our results indicate that this exhumation is possibly led by the Pacific plate subduction combined with intracontinental orogeny associated with asthenospheric upwelling.