Origin of the magnetite-sulfides composite grains in the Moho transition zone dunite from Wadi Thuqbah, the northern Oman ophiolite

Abstract

We found a sulfide-rich dunite from Wadi Thuqbah, the northern Oman ophiolite which is within the Moho transition zone. The dunite contains about 2 mode % magnetite-sulfides composite grains. The composite grains are composed of Pentlandite-pyrrhotite intergrowth (PPI), magnetite (Mt) and homogeneous pyrrhotite (HP). PPI shows complicated exsolutions of pentlandite and pyrrhotite, and is cut by Mt. The texture of PPI was formed by decomposition of MSS at low temperatures. Mt has not been added to chromian spinel grains, deny a possibility of later addition of Mt to sulfide composite grains. The magnetite-sulfide composite grains were possibly formed by solidification of separated sulfide-magnetite melt, the Mt has filled cracks of sulfide parts that suffered from brittle deformation.