Sherif KHARBISH
Geology Department, Faculty of Science, Suez University, Suez, 43518, Egypt; e-mail: sherifkhabrish@hotmail.com

METAMORPHISM AND GEOCHEMICAL ASPECTS ON NEOPROTEROZOIC SERPENTINITES HOSTED CHROME SPINEL FROM GABAL AL-DEGHEIMI, EASTERN DESERT, EGYPT

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Petrographic and geochemical studies of the chrome (Cr)-spinel in serpentinites from the Gabal Al-Degheimi, in the central Eastern Desert of Egypt, are made to evaluate their textural and compositionalvariations Cr-spinel cores do not appear to have re-equilibrated completely with the metamorphic spinelrims and surrounding silicates, suggesting relic magmatic composition unaffected by metamorphism.Accessory Cr-spinel in the serpentinites is characterized by Cr (0.60-0.78) and Mg (0.54-0.68). NormalizedREE patterns and the low abundances of Ti, Na, Nd, Sm, Lu and Hf of serpentinites and Cr-spinel corecompositions suggest that Gabal Al-Degheimi serpentinites are of ophiolitic origin and represent relicts of areduced depleted harzburgite to dunite mantle peridotites formed in an oceanic suprasubduction zone(marginal-basin) tectonic environment that experienced high degrees of partial melting in excess of 22%.Textural and compositional features of the Cr-spinels suggest transitional greenschist-amphibolite up tolower amphibolite facies metamorphism, which is isofacial with the country rocks.