Thermal history and exhumation processes in the Chinese South Tianshan: constraints from 40Ar/39Ar and (U-Th)/He ages

The Chinese South Tianshan (CSTS) on the southwestern margin of the Central Asian Orogenic Belt (CAOB) is a vital tectonic location to elucidate the links between the prevailing Cimmerian collisional orogenic process and uplift mechanisms in the whole CAOB. To constrain the CSTS exhumation processes, we determined systematic zircon U-Pb, biotite and K-feldspar 40Ar/39Ar and apatite (U-Th)/He ages of plutons from Hark and Erbin Mountains in the CSTS and the Bachu Uplift in the Tarim Basin (for comparative study). The results reveal spatial and temporal disparities in the CSTS thermal history and exhumation processes, which can be classified into three stages. Stage I (P-1): intrusive bodies experienced magmatic cooling episodes after emplacement, revealing a deeper emplacement location for the pluton in Hark Mountain than in Erbin Mountain and the Bachu Uplift. Stage II (P-2-K): Hark Mountain experienced rapid cooling and exhumation processes (3.0 degrees C/Ma, 0.14 mm/year) compared with the Erbin Mountain (2.0 degrees C/Ma, 0.09 mm/year) and Bachu Uplift (1.8 degrees C/Ma, 0.07 mm/year), resulted from the Qiangtang-Kunlun collision and Qiangtang-Lhasa collision in the south. Stage III (Cz): Rapid Cenozoic exhumation in the CSTS weakened eastward; the latest and most rapid uplift occurred in Hark Mountain to the west (8.6 Ma, 5.5 degrees C/Ma), after the eastern Ouxidaban pluton (31.1 Ma) and Erbin Mountain (56.4 Ma, 0.8 degrees C/Ma), possibly related to the remote effects of the India-Eurasia collision. Further, the northern Bachu Uplift could have been rigid enough that could transmit the driving forces in southern Eurasia from south to north during the Cenozoic.