The petrology of two back-arc basins of the northern Philippine Sea.

Abstract

Rather than mantle upwelling driven largely by separation of crustal plates, mantle counterflow and hydrous remelting above a descending slab are considered mainly responsible for convection in back-arc basins. Differences in the chemistry of contemporaneous basement rocks drilled in the Shikoku and Minami-Daito back-arc basins are attributed to differences in the influence on magmatic processes exerted by thick oceanic lithosphere and the absence of a well-defined spreading centre in the Minami-Daito basin, as distinct from the relatively thin lithosphere and well-developed spreading centre in the Shikoku basin. -M.S.