Primitive basaltic melts included in podiform chromites from the Oman Ophiolite

In an attempt to characterize the composition of the parental melts of ophiolitic chromitites and their tectonic setting, we have undertaken a study of polymineralic solid inclusions trapped in chromites from the Oman Ophiolite (Sumail nappe). High-temperature experiments performed on inclusions show that they result from post-entrapment crystallization of homogeneous basaltic melts with primitive compositions (Mg# = 63.5–66.8). The primary nature of the inclusions, demonstrated by their distribution outlining the crystallographic zones of mineral growth, indicates that the trapped melts represent small amounts of the parental liquids of the host chromites. Homogenised melt inclusions show depleted trace element patterns, with significant Nb depletions, characteristic of a subduction-related origin. These observations indicate that chromite deposits from Oman harzburgitic ophiolites may have formed in a geodynamic setting akin to present-day back-arc basins.