Can Archean granulites be direct crystallization products from a sialic magma layer?

Archean granulite terrains are generally dominated by charnockite-enderbite suites. These rocks are geochemically similar to the tonalite-trondhjemite-granodiorite (TTG) gneisses of Archean cratons. Following an open-system fractional crystallization model for formation of TTG crust through solidification from a shallow-level tonalitic magma ocean, we propose that such granulites could have formed by crystallization at depth at the base of the same magma layer, which is undergoing convection. -from Authors