Geochemical studies of abyssal lavas recovered by DSRV Alvin from eastern Galapagos rift, Inca transform, and Ecuador rift. 3. Trace element abundances and petrogenesis.

Abstract

Glassy to sparsely phyric submarine lavas were recovered from 9 Alvin dive sites located along the E Galapagos rift and at the intersection with the Inca transform. Magma mixing has occurred on a small scale in the evolved liquids and can partially explain the chemical characteristics of basaltic andesites. All data point to extensive amounts of fractional crystallization during the evolution of these lavas; however, mantle heterogeneity and other processes such as partial melting, open-system fractional crystallization, and convection-driven thermogravitational diffusion may also play minor roles in influencing magmatic evolution. Three subrift, accretionary magmatic domains result from the interplay of transform effects and attempted propagation. The chemistry of lavas is a direct consequence of the magmatic domain that prevails along an accretionary boundary. -from Authors