[SCG56-P10] First geochemical and mineralogical results of Oman Crust-Mantle transition: holes CM1A and CM2B characterization aboard DV-Chikyu_ Oman Drilling Project, Phase 2 Leg3
Keywords:Oman crust-mantle transition, gabbros, dunite, harzburgite, Oman ophiolite, XRF, XRD, ICP-MS, LA-ICP-MS, Chikyu_OmanDP
Samples from holes CM1A and CM2B have a large petrological and chemical variability, mainly reflecting the different rock types, especially across the crust-mantle transition. CM1A and CM2B volatile element contents reflect extensive serpentinization linked to interaction with H2O-rich fluids, and abundant carbonate veins downhole, suggesting an association between CO2-rich fluids and serpentinization. Whole-rock and ortho- and clinopyroxene trace element abundances are similar to Oman ophiolite compositions described in previous studies. All gabbroic domains display nearly parallel REE patterns with a strong depletion in HFSE relative to REE. Dunites display variable trace element contents and REE patterns, negative or positive anomalies in Eu and commonly moderate to strong positive anomalies in U, Pb, Sr and Ti. The variation of REE concentrations and patterns observed in Oman dunites could be explained by melt-rock reactions leading to dunite formation, after the dissolution of orthopyroxene in harzburgite and interaction with interstitial melt.