Spinels from cumulus and non-cumulus members of the 0thris ophiolite display a considerable variation in composition. Cumulus pierites and gabbros contain either a primary chromite and/or a reaction spinel formed by reaction with co-existing sili?ate,-" (Cr--A1 varia tion) or intercumulus liquid (Cr--Fe variation). Non-cumulus peridotites contain spinels which vary along a Cr--A1 trend. Harzbur...

[1] One process for the formation of continental crust is the accretion of arc terranes at continental margins. A longstanding problem with this model is that although the composition of the continental crust is andesitic, the majority of arc lavas are basaltic. Moreover, those arc lavas that are andesitic tend to be evolved (lower Mg #) compared to the continental crust. Continental crust can ...

The Neoproterozoic rocks of the Bir Madi area, south Eastern Desert, comprise a metagabbrodiorite complex (GDC) and a tonalite-granodiorite suite (TGrS). The GDC has a weak tholeiitic to strong calc-alkaline character and is made up of olivine gabbro, hornblende gabbro, diorite and monzodiorite. The olivine gabbro is characterized by abundance of augite and labradorite with pseudomorphic serpen...

Current knowledge on the solidus temperature for carbonated eclogites suggests that carbonatitic liquids should not form from a subducted oceanic lithosphere at sub-arc depth. However, the oceanic crust includes a range of gabbroic rocks, altered on rifts and transforms, with large amounts of anorthite-rich plagioclase forming epidote on metamorphism. Epidote disappearance with pressure depends...