Petrography, mineralogy, and fluid inclusions of Rod El-Biram muscovite pegmatites, Central Eastern Desert, Egypt.

Abstract

Wadi Rod El-Biram pegmatites belong to muscovite pegmatite, which are located at the Central Eastern Desert between latitudes 25o 8` 30`` and 25o 11` N and longitudes 34o and 34o 10`E. They occur as rounded or elongated zoned masses and they invade both alkali-feldspar granites and ophiolitic serpentinites. The zoned bodies consist of a) wall zone, which is composed mainly of albite and muscovite. Greisenized pockets are recorded between alkali-feldspar granites and the wall zone, b) the intermediate zone consists mainly of K-feldspar with subordinate quartz and muscovite, c) the core zone consists mainly of amoeboid-shaped milky quartz, which may enclose isolated flakes and/or nests of muscovite. The heavy minerals contain garnet, fluorite, zircon, and rutile minerals. Garnet may be derived either by crystallization with muscovite as an alternative to biotite from volatile enriched melt or by assimilation from country rocks. Fluid inclusions are represented by coexisting of two-phase and three-phase inclusions. The estimated conditions of trapping using the intersection of isochors are at temperature range between (360-420 oC), and pressure between (600-2100 bars). Rod El-Biram muscovites have primary magmatic origin. The trend of the granitic rock and the associated pegmatites in Rod El-Biram is not compatible with the fractional crystallization, so the pegmatites have a different source rather than the granitic melt. These S-type pegmatites may have originated by partial melting of a metasedimentary source. The chemical composition K-feldspars and physical testing confirms the suitability of the feldspars from Rod El-Biram pegmatites for floor rather than wall ceramic tiles.