S2: Water Rock Interaction (Special Session)

[S2P-02] Formation conditions of epidote in lower crustal olivine gabbros of the Oman ophiolite

*Yamato Tateishi¹, Toshio Nozaka¹ (1. Okayama Univ.)

Keywords:Oman Drilling Project, lower crust, olivine gabbro, alteration, epidote

In the Oman Drilling Project Holes GT1-3, epidote is distributed widely in upper levels of the lower crustal section but exclusively within or in proximity to veins and cataclastic zones in lower levels. In lower-level olivine gabbros, prehnite and chlorite replacing plagioclase show a close association with serpentine replacing olivine, whereas epidote, if any, never coexists with serpentine. Thermodynamic modeling indicates that epidote could form at conditions with higher oxygen fugacity than serpentinization and prehnite formation conditions.