Saleh and El-Nisr
Greener Journal of Geology and Earth Sciences Vol. 1 (2), pp. 023-042, September 2013.
ISSN: 2354-2268 © 2013 Greener Journals
Manuscript Number: 081213777
Tow Mica Granites, Southeastern Desert, Egypt: Geochemistry and Spectrometric Prospecting
Gehad M. Saleh*1 and Said A. El-Nisr2,3
1Nuclear Materials Authority, P.O.Box: 530 El Maadi, Cairo, Egypt.
2Geology Department, Faculty of Science, Alexandria University, Egypt.
3Consultant at the Strategic Studies Center- AbdelAziz King Univ.-Saudi Arabia.
*Corresponding Author’s Email: drgehad_m @ yahoo.com
Tow mica granites of the Abu Rusheid - Eir Arib district in the Southeastern Desert of Egypt, cut pre-existing faults, and their contacts with the country rocks are sharp and lack contact metamorphism. They were intruded into a low - to high grade metamorphosed ophiolitic mélange and a high - grade metamorphosed meta-sedimentary succession of biotite schist. Petrographically, the phase is strikingly similar and consists of alkali feldspar, quartz, plagioclase, muscovite and biotite. Zircon, garnet, apatite, allanite, titanite and opaque’s are accessories. Abu Rusheid - Eir Arib tow mica granites are characterized by strongly peraluminous compositions; contain miarolitic cavities and pegmatitic patches, suggesting the release of aqueous fluids from the down going slab during subduction. The investigated rock has low K/Rb and high Zr /Y ratios reflecting a typical mature continental - arc environment. The REEs pattern is characterized by fractionated LREEs and relatively flat HREEs with pronounced negative Eu anomalies. The geochemistry of REEs reflects the behavior of accessories and key major minerals such as garnet and feldspars, and may therefore give valuable information about the conditions of partial melting, melt segregation and crystallization of granite magmas in different crustal regimes. The study presents the surface distribution of the total gamma radiation Tc, K, U and Th in Abu Rusheid - Eir Arib two – mica peraluminous granites. The geochemistry of Zr/U, Zr/Th, Ce/U and Ce/Th against either U or Th in suite exhibits significant negative correlations, indicating that both elements are not preferentially hosted in accessory zircon or monazite, but could be associated with major rock forming minerals such as biotite, muscovite, plagioclase and quartz, or U is situated within labile sites within the granites. The distribution of uranium, thorium and their ratios in the garnetiferous granite reveal that this granite is considered as fertile granites and reflects the amount of remobilization that took place within the granites.
Keywords: Tow mica granites, Magmatic differentiation, Total gamma radiation and Egypt.