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

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 pm, 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 (similar to 210-110 degrees C) during similar to 90-57 Ma. Stage two was a relatively slow cooling period (similar to 110-60 degrees C) occurred between similar to 57 Ma and 20 Ma, suggesting that the granitoids had been exhumed to depths of similar to 1-2 km. The final stage was a cooling period (60-20 degrees C) occurred since the Miocene, which bring studied samples to the Earth's surface at an accelerated exhumation rate. The estimated maximum exhumation is similar to 5 km assuming a steady-state geothermal gradient of 35 degrees C/km. Our results indicate that this exhumation is possibly led by the Pacific plate subduction combined with intracontinental orogeny associated with asthenospheric upwelling. (C) 2011 Elsevier Ltd. All rights reserved.