Thermochronology of cordilleran metamorphic core complexes: example of Song Chay massif in Northern Vietnam

Abstract

Based on the reconstruction of the thermal evolution of the Song-Chai granitoid massif (Northern Vietnam) the long-term existence of granitoid magma at deep levels of the Earths crust (H = 15-20 km, t ~ 20-50 Ma) is established. Geodynamic analysis and mathematical modeling of thermal history of the granitoid batholith cooling shows that the magmatic chamber should be considered as thermal trap on the lower level of the earths crust, preserving residual granite melts for a long time. Activation of the magmatic chamber occurs in post-collisional strike-slip tectonics zones and is associated by tectonic exhumation of large segments of the earths crust. Ultimately, this leads to the transformation of the batholith into Cordilleran type metamorphic core complexes, emplacement of residual rare-metal melts and the formation of commercial deposits.