الفهرس 
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Abstract
The Studied rod Umm Elfarag pegmatites occur as vein or dyke-like bodies intersecting the younfer pink granit or the older grey granite host rocks . All these pegmatite are muscovite-bearing type.
he main findings and conclusions of the present study can be . outlinf:d in the following items:
1- Th~ studied Rod Umm EI Farag pegmatites occur as vein or dyke -like bodies intersecting the younger pink granite or the older grey granite host rocks. All these pegmatite are muscovite - bearing type.
2- All the studied pegmatites of Rod Umm EI Farage area are of the zoned type, and somewhat similar in composition. The characters of each of these zones can be summarized as follows:
- The border zone occurs at the contact with the granitic host rocks and is mainly composed of albite and quartz with relics of microcline within some albite crystals.
- The wall zone consists mainly of albite, microcline perthite with a few amount of muscovite
The formation of muscovite - bearing pegmatites of Rod Umm EI Farag area is related to two subsequent process starting as late magmatic and terminated as hydrothermal stages. The magmatic stage of pegmatite formation is most probably related to the development of pink granite host rock as a late magmatic stage of these younger granites. This is indicated from the field relations and association of aplite selvage in contact with pegmatite in the pink granite host rock. A post·magmatic hydrothermal stage includes the substitution of the early formed pegmatite minerals of the late magmatic stage is indicafed from the transformation of the early formed microcline to albite (albitization) and subsequent formation of muscovite (greisenization). This is proved from’the presence of relics of the early formed microcline within albite aggregates and also from the presence of veinlets of either microcline perthite or albite within the late formed muscovite.
4- The formation of the first recorded euxenite, minor fluorite, topaz, beryl in the muscovite - bearing pegmatite in this area is most probably related to the later withdrawals of more aqueous pegmatitic fractions of the pegmatite melts.
5- A bimetasomatic effect between the older grey granite host rock and the pegmatite is indicated from the presence of some almandine garnet in the outer pegmatite zones at their contact surface with the grey granite. Garnet is most probably formed after biotite, that commonly occurs in the grey granite and also noted from the presence of relics of the mineral biotite within some garnet crystals. Again, it is also chemically proved by the relative enrichment in Ca, Mg and Sr ( which are present in appreciable amounts in the grey granite) in the outer pegmatite zone and at the contact surfaces between them. On the other hand, the contact effect of pegmatite on the grey granite host rock is illustrated by the addition of excess quartz