Geochemical evidence in clinopyroxenes from gabbroic sequence for two distinct magmatisms in the Oman ophiolite

In the Oman ophiolite, one of the best preserved and most studied ophiolites in the world, two distinct petrogenetic suites of gabbroic rocks from the layered gabbro sequence of the Wadi Haymiliyah section is established using trace element chemistry of Ca-rich clinopyroxenes. The earlier GB1 suite is characterized by plagioclase with lower An (Ca/(Ca + Na)) content and clinopyroxene with low large-ion lithophile elements (LILE) concentrations. The later DWGB2 suite contains plagioclase with rather high An content and clinopyroxene with high LILE. This difference in clinopyroxene chemistry can be extended to the extrusive rocks in this section: lower, (earlier) HV1 suite with low LILE clinopyroxene and upper (later) HV2 suite with high LILE clinopyroxene. Difference in LILE concentration of clinopyroxenes is essentially due to geochemical difference in parental magmas. The GB1/HV1 suites formed at fast-spreading MOR setting and DWGB2/HV2 suites at SSZ setting, supporting a model of transition from mid-oceanic ridge to supra-subduction zone settings of the Oman ophiolite. Our results indicate that geochemical signature of clinopyroxene is a very strong tool for identification of tectonic setting of ophiolites.