Sr, Nd and Pb isotopic constraints in the genesis of a calc-alkaline plutonic suite in Oman Ophiolite related to the obduction process

Abstract

K-mineral bearing felsic intrusions in the Oman Ophiolite (mainly from the Khawr Fakkan Massif) have been studied for incompatible elements, and Pb, Sr, Nd isotopes. Metamorphic schists and quartzites having reached anatexis, belonging to the sole of the same massif are also studied for comparison. Both incompatible element and isotopic data indicate that these intrusive bodies are fundamentally different from oceanic plagiogranites. Hygromagmaphile elements are globally depleted relative to oceanic magmas but they present a relative enrichment in highly incompatible elements (Th, U and LREE). The least differentiated samples have a V positive anomaly indicative of high oxygen fugacity during genesis. The lead isotopic compositions are characterized by radiogenic lead enrichment suggesting the effect of a crustal component similar to that of the metasediments of the metamorphic soles. On the other hand, the initial Sr and Nd isotopic compositions are dominated by a mantle component. Melting of the metamorphic sole would best account for the genesis of these intrusions. -from Authors