Metasomatic alteration and immediate exhumation of forearc peridotites of the Oeyama ophiolite

Abstract

Forearc peridotites from the Oeyama ophiolite show the following facts: formation of high-temperature metasomatic minerals such as amphiboles, phlogopite, olivine and orthopyroxene; a systematic variation of amphibole compositions corresponding with texture and mineral assemblage; the presence of fine-grained olivine veins penetrating primary olivine; and the presence of Mg-Fe diffusion zones in olivine host crystals of the veins. Based on texture, chemical compositions of minerals and diffusion models of olivine, it is inferred that the peridotites were subjected to a sequence of metasomatic alteration and plastic deformation, and that their exhumation took place during of immediately after the alteration.