Chromite-rich and chromite-poor ophiolites: the Oman case

Abstract

Chromite deposits in Oman belong dominantly to the concordant structural type, meaning that these have been intensely deformed by plastic flow and tectonically rotated to become parallel to the peridotite foliation. This occurred soon after their formation within the transition zone below the ridge of origin. Subconcordant and discordant pods are also present. The latter have preserved delicate magmatic structures showing that they have only been little deformed after their formation in melt-carrying conduits. Regionally, the chromite deposits have been dominantly found, so far, in restricted areas. Maqsad, one of the largest chromite districts, was also an area of mantle diapirism below the ridge of origin. The chromite deposits are restricted to the Harzburgite Ophiolite Type (HOT) in which chromium has passed into the melt. Although Oman belongs to the HOT group, it seems to have been a particularly fast spreading HOT. It is suggested that in such a situation the transition zone could have remained too hot to allow for abundant chromite formation. -from Authors