The exhumation and uplift of the southern Shigu complex since Early Cretaceous evidenced by zircon and apatite fission track

The Shigu complex lies on the southeastern margin of the Tibetan Plateau,and is mainly distributed in Shigu and Zhongdian areas. The complex has experienced polyphase superposition of metamorphism and deformation. In order to reveal the low temperature thermal evolution and exhumation history at the shallow crustal level of the complex and correctly understand the exhumation and tectonic evolution of the metamorphic dome in eastern Tibet,the authors collected zircon and apatite fission track samples for the fission track analysis along the Shigu Town-Labazhi section. The analytical results show that the Shigu complex firstly experienced a slow cooling and exhumation from Early Cretaceous (133~145Ma) to Oligocene (31Ma),and a relatively rapid cooling process started from Oligocene. Time-temperature history simulated by inverse modeling of apatite fission track also reflects a relatively rapid cooling process at the second stage. From regional structural analysis,it is suggested that the far-field effects of the collision between the Lhasa and Qiangtang plates may have strongly affected the Early Cretaceous exhumation of the complex. Furthermore,the Indian-Eurasian collision and post-collisional effects had profound effects on the Cenozoic exhumation of the complex.