Cenozoic thermal-rheological evolution of the coastal cathaysia block of East Asia: geodynamic implications

The thermal-rheological structure of the continental lithosphere is an important indicator of geodynamic processes. Tectonic compression and extension may change thermal-rheological structure of lithosphere. However, the thermal-rheological evolution over geological time may be difficult to determine because of overprints of subsequent geological events. Mantle xenolith temperature and pressure conditions can differentiate the lithospheric thermal structure over geological time and indicate the lithospheric rheological strength. Chronological and temperature-pressure condition data from 11 mantle xenoliths in Cenozoic basalts from the Wuyishan terrane (WYT) and coastal terrane (CT) on both sides of the Zhenghe-Dapu Fault (ZDF) in the Cathaysia Block indicate that these terranes have experienced distinct thermal-rheological evolution since the Eocene. Moreover, the thermal-rheological evolution of the CT and WTY were differently influenced by the West Pacific tectonic domain, respectively, because the ZDF has been relatively active since 23 Ma and thus has partly accommodated and thus reduced the tectonic impact of Eurasia-Pacific convergence. Therefore, we classified the thermal-rheological structural evolution of the Cathaysia Block into three stages (35.5–20 Ma, 20–6.5 Ma, and 6.5–0 Ma) that sequentially recorded the opening and closing dynamics of the northeastern margin of the South China Sea and uplift of Taiwan Island on the eastern margin of Eurasia.