Silicic Magma Formation in Overthickened Crust: Melting of Charnockite and Leucogranite at 15, 20 and 25 kbar

Two models of silicic magma formation have been experimentally tested: (1) generation of A-type granite magma by partial melting of crustal source rocks at depths >50 km; (2) production of syenite magma by partial melting of quartzofeldspathic rocks at pressures >15 kbar. Melting experiments at 15, 20 and 25 kbar were performed on Archaean biotite-bearing charnockite of opx-bearing granodiorite composition, and on leucogranite. Most experiments were conducted with oxalic acid (OA) to provide 2 wt % H