The Exhumation Process of Mufushan Granite in Jiangnan Uplift Since Cenozoic: Evidence from Low‐Temperature Thermochronology

Abstract

AbstractJiangnan uplift located in the collision zone between Yangtze and Cathaysia block is the key to interpret the tectonic evolution of South China block. The Cenozoic thermal history and the uplift processes of Mufushan pluton are constrained by the combination of analysis of apatite fission track and (U‐Th‐Sm)/He ages with modeling of fission track length distribution. Based on the analysis of thermochronological dating and regional tectonic setting, the authors probed into the relationship between the thermochronological evolution and the tectonic development. The exhumation of plutons arrived at about 4800 m since 80 Ma, and the uplift processes were not uniform in space, and different plutons had somewhat different uplift processes. Thermal history modeling of the AFT data shows that the Mufushan pluton experienced three episodes of cooling event, two rapid exhumation events happened in Upper Cretaceous‐Paleocene (about 80∼50 Ma) and Upper Miocene (since 10 Ma). There is a period of relative thermal stability between 50 and 10 Ma. The first stage of rapid uplifting during 80∼50 Ma in this region is coeval with extension episode of Mid‐Upper Yangtze during Himalayan which resulted in the formation of fault basin and exhumation of shoulder block; the Upper Miocene rapid cooling since 10 Ma is attributed to the westward movement and subduction of Pacific plate. The uplift and exhumation of Mufushan pluton since Late Yanshanian led to a good deposition response in basins and the cooling events of three phases just coincided with the regional tectonic settings of study area.