Formation of discordant chromitite as an early sub-arc mantle process: An example from northern Oman ophiolite

Abstract

Ophiolitic chromitites are classified into two types, concordant and discordant, in terms of structural attitude with surrounding mantle harzburgite. Spinel chemistry of discordant chromitites, dunite envelopes and surrounding harzburgites from Oman ophiolite, indicates that discordant chromitites were formed by arc-related magma. In a deeper mantle section along Wadi Hilti, two types of harzburgites, arc-type and oceanic-type, are exposed near the discordant and concordant chromitites in the same cliff, respectively. Contact of two types of harzburgites shows a gradual change in spinel chemistry. This indicates that pre-existing oceanic harzburgite was modified by arc magma.