Uprising period and elevation of the Wenyu granitic pluton in the Xiaoqinling District, Central China

Abstract

Xiaoqinling District is an important gold-producing area in China. It ranks second to Jiaodong with regard to gold deposits. The uprising period of the Wenyu granitic pluton and the wall-rocks of the deposit, as well as the mineralizing depth and reserved place of gold ore bodies, are significant to ore exploration. Fission-track (FT) analysis of zircons and apatites of granitic rocks from the Wenyu granitic pluton shows that apatite FT (AFT) data modeling indicates a rapid cooling rate of 20°C/Ma from 138 to 120 Ma after emplacement at 138 Ma. Thermal evolution and inversion curves suggest a secondary phase of fast cooling and uprising from 45 to 35 Ma, and 35 Ma, respectively, with a cooling rate of 6.7°C/Ma and a denudation quantity of ∼4.3 km. The last cooling phase took place from <4 Ma, with an average cooling rate of ∼11.3°C/Ma and a denudation amount of 1.3 km. Total exhumation quantity of 5.6 km and uprising elevation of 7.3 km are similar to the estimated results of fluid inclusions from the Dongtongyu and Wenyu gold deposits. The 39Ar/40Ar dating of sericite from the fault planes of the Xunmadao-Xiaohe and Taiyao faults demonstrate two uprising activities of the ore-host metamorphic complex. The Huashan and Wenyu granitic plutons intensively occurred during 77 and 45 Ma, respectively. These data sets are valuable for understanding the uplifting process and for preserving gold ore bodies in the Xiaoqinling area, as well as for further studies on tectonic evolutions of the Taihua Complex and the Qinling-Dabie Orogen.