The genesis of the calc-alkaline rock suite

Abstract

The derivation of an island arc calc-alkaline suite from an alkaline parental magna source is suggested from petrological and mineralogical evidence in the Lesser Antilles. Possible sources are discussed, and a partial melt from the Upper Mantle, rather than a descending oceanic crustal plate preferred. The consequence of the incomplete melting of a plate in a subduction zone is the production of local heterogeneity in the Upper Mantle, leading to geographical chemical differences in magmas produced in partial melting episodes. The calc-alkaline trend apparently reflects the physical as much as the chemical environment of fractionation. Show more