Recycled oceanic crust as a source for tonalite intrusions in the mantle section of the Khor Fakkan block, Semail ophiolite (UAE)

摘要: Abstract Several types of felsic granitoid rocks have been recognized, intrusive in both the mantle and crustal sequence Semail ophiolite. models proposed for source this suite tonalites, granodiorites, trondhjemites intrusions, however their genesis is still not clearly understood. The sampled Dadnah tonalites that intruded section ophiolite display arc-type geochemical characteristics, are high siliceous, low-potassic, metaluminous to weakly peraluminous, enriched LILE, show positive peaks Ba, Pb, Eu, negative troughs U, Ti occur with low δ18OH2O, moderate eSr eNd values. They crystallized at temperatures range from ∼550 °C ∼720 °C pressure ranging 4.4 kbar 6.5 kbar. isotopic ages our tonalite samples between 98.6 Ma 94.9 Ma, slightly older overlapping age metamorphic sole. Our field observations, mineralogical, petrological, geochemical, melt inclusion data suggest formed by partial melting (∼10%–15% continuous or ∼12% batch melting), accumulation plagioclase, fractional crystallization (∼55%–57%), interaction host harzburgites. These were end result subsequent contamination mixing ∼4% oceanic sediments ∼96% lithosphere subducted slab. This MORB-type slab composed ∼97% recycled crust ∼3% overlying mantle. We a possible protolith these was basaltic lavas melted during initial stages supra-subduction zone (SSZ), which forming synchronously spreading ridge axis. melts mildly modified due degree lithospheric Subsequently, emplaced upper part geochemically distinct other granitoids south.