Lithospheric delamination controls the Mesozoic Magmatic Province in South China

It is known that the current lithosphere of the South China Block is as thin as 60-70 km, yet what mechanisms modified the lithospheric structure remain highly controversial. Here we apply a new joint seismic inversion algorithm of body wave arrival times, surface wave dispersion data and teleseismic receiver functions to image lithosphere velocity structure of South China. Tabular high-velocity anomalies are imaged at depths of ~90–150 km in the asthenosphere beneath the convergent belt between the Yangtze and Cathaysia blocks that remain weakly connected with the stable Yangtze lithosphere. Based on obtained seismic images and available geochemical data, we interpret these detached fast wavespeed anomalies as partially destabilized lower lithosphere that initially delaminated at 180–170 Ma and has relaminated to their original position after warming up in the mantle by now. We conclude that delamination is the most plausible mechanism for the lithospheric modification and the formation of a Mesozoic Basin and Range-style magmatic province in South China by triggering adiabatic upwelling of the asthenosphere and consequent lithospheric extension and extensive melting of the overlying crust. Moreover, it also has a major control on the rich deposits of various metals in South China.