True K-feldspar granites in oceanic crust (Masirah ophiolite, Sultanate of Oman): A UPb and SmNd isotope study

This paper presents UPb and SmNd isotope data of various rock types from the Masirah ophiolite, Sultanate of Oman. The study aimed at delineating the source and genesis of K-feldspar granites which are emplaced in the oceanic crust. Theses granites clearly intruded the sequence prior to its obduction and show initial Pb and Nd isotopic compositions which exclude significant continental crust contribution during their generation. Both geochronological and geochemical data are in conflict with the assumption of a continuous differentiation process for granite generation, i.e. the granites are not the final differentiation chain products of oceanic crust generation. Their emplacement into previously thinned oceanic crust and their possible genetic relationship with partly explosive alkaline volcanism suggest that the Masirah granites were generated by partial melting at depth as a consequence of transtensional movements associated with transform faults. These faults may have favored deep hydration of the crust which initiated melting, probably enhanced by heat transfer from a nearby hotspot.