Genesis of granulite in Himalayan lower crust: Evidence from experimental study at high temperature and high pressure

Here we present an insight into the genesis of Himalayan granulitic lower crust based on the experimental studies on the dehydration melting of natural biotiteplagioclase gneiss performed at the temperatures of 770-980℃ and the pressures of 1.0-1.4 GPa. The experiments produce peraluminous granitic melt and residual phase assemblage (Pl+Qz+Gat+Bio+Opx±Cpx+Ilm/Rut±Kfs). The residual mineral assemblage is similar to those of granulites observed at the eastern and western Himalayan syntaxises, and the chemical compositions of characteristic minerals-garnet and pyroxene in the residual phase and the granulite are identical. Additionally, the modeled wave velocities of the residual phase assemblage are comparable well with those of the top part of lower crust beneath Himalayas.Hence, we suggest that (1) the top part of lower crust beneath Himalayas is probably made up of garnet-bearing intermediate granulite; (2) the formations of granulite and leucogranites in Himalayas are interrelated as the results of crustal anatexis; and (3) dehydration melting of biotite-plagioclase gneiss is an important process to form granulitic lower crust, to reconstitute and adjust the crustal texture. Moreover, experimental results can provide constraints on determining the P-T conditions of Himalayan crustal anatexis.