Theories and evolution of granite formation

The traditional basalt differentiation theory has been superseded by the deep crustal melting theory. A four-stage evolutionary model proposed in 2024 indicates that:

Source rocks undergo partial melting at 800-900°C, producing an initial melt.

The melt undergoes amphibole-dominated fractional crystallization in a lower crustal magma chamber.

The silica-rich melt ascends along structural weak zones.

It intrudes into the middle and upper crust, forming batholiths or dikes.

Studies of the Gangdese island arc show that amphibole fractional crystallization controls the increase in SiO₂ content, and the residual melt, through apatite separation, increases the Sr/Y ratio, forming adakitic granitoids.