Geochemistry, Petrogenesis and Metallogenesis of the Wadi Qutabah Gabbroic Intrusion and Associated Ni-Cu Deposits, North West Yemen

The Wadi Qutabah gabbroic intrusion associated with magmatic Ni-Cu sulfide deposit is located in the northwest of Yemen, about 60 km. of Sana’a City. Petrographic examination shows the gabbroic rocks are composed mainly of plagioclase, clinopyroxene orthopyroxene and hornblende. Two main types of sulfide mineralization have been recognized within gabbroic rocks; disseminated and massive sulfides. The principal ore minerals are pyrrhotite, pentlandite, chalcopyrite and magnetite. The chemical compositions of the gabbroic rocks represent SiO2 (47.68 - 53.13 wt. %), MgO (1.97 - 9.98 wt. %) Al2O3 (16.57 - 26.76 wt. %), Fe2O3 (2.0 - 13.35 wt. %) and TiO2 (0.54 - 3.07 wt. %). The results of chemical analysis of the sulfides represent Ni (0.40 – 1.54 wt. %), Cu (0.06 – 2.46 wt. %) and Co (0.08 – 0.180 wt. %). The Wadi Qutabah gabbroic intrusion is enriched in light rare earth elements (LREE) relative to heavy rare earth elements (HREE), and exhibit positive Nb, Ta and Ti anomalies and negative Zr and Hf anomalies. Major oxide, trace element and REE data are suggestive of oceanic island evolved basalt as the parent for these gabbros. The mineralogy and tectonic discrimination diagrams suggest within plate basalt tholeiitic.