Origin Of Large Wehrlitic Intrusions From The Wadi Barghah To Salahi Area In The Northern Oman Ophiolite

Wehrlitic intrusions constitute an important element of oceanic lower crust of the Oman Ophiolite, and numerous such dunite and plagioclase wehrlitic intrusions cut gabbro units in the northern Salahi Block of this ophiolite. For the first time, we describe a large wehrlitic intrusion (the Barghah complex) that has disturbed and folded surrounding gabbro units around this complex. The Barghah complex contains many gabbro blocks that record evidence of magma mingling. The crystallization sequence of the wehrlitic intrusions is olivine followed by co-crystallization of plagioclase and clinopyroxene. The forsterite content of olivine and the Mg# of clinopyroxene are more evolved than in rocks from the Moho Transition Zone (MTZ). TiO2 and Na2O contents of clinopyroxene are similar to those of the MTZ and are characterized by wide compositional variability over a narrow range of Mg#, which is indicative of melt-mantle interaction. Compositional co-variation of plagioclase and olivine in the wehrlitic intrusions has a similar signature to that of V1 magmatism (ocean ridge stage). In light of these observations, we conclude that the wehrlitic intrusions are the product of off-axis magmatism. Inversion tectonics that led to a transition from spreading to compression may have accelerated the emplacement of the wehrlitic intrusions.