The timing and mechanisms of the uplift of the Tibetan Plateau are important for understanding orogenic geodynamics and environmental responses. Potassic−ultrapotassic volcanic rocks across the Tibetan Plateau have often been utilized to trace the plateau’s uplift due to their close association with lithospheric thinning. However, it remains unclear whether significant exhumation occurred during the eruption of these volcanic rocks. This study examines a newly identified Miocene pyroxene syenite intrusion containing granite xenoliths in eastern Qiangtang, Tibetan Plateau, integrating thermochronology, thermal modeling, mineral analyses, and thermodynamic simulations. The results indicate that the thermochronological ages of the pyroxene syenite largely match its crystallization age, and it experienced a period of rapid cooling at ca. 12−10 Ma. This cooling phase was associated with substantial exhumation of the pyroxene syenite, as inferred from the crystallization depth of 10−13 km, which was determined using clinopyroxene and biotite barometers. Thermodynamic modeling has identified four drivers of exhumation: (1) surface erosion, (2) lithospheric delamination, (3) magmatic underplating, and (4) Indian plate underthrusting. Collectively, these processes drove middle−late Miocene exhumation of the syenite and at least 700 m of surface uplift in eastern Qiangtang. Our study helps not only to elucidate the geodynamic mechanisms driving the uplift of the Tibetan Plateau, but also to interpret thermochronological data.
Gong et al. (Mon,) studied this question.