HR: 1400h
AN: V53B-12    [Abstracts]
TI: Petrologic characterization of A-type granites from southern Sinai, Egypt
AU: Ibrahim, T
EM: elsahabi@yahoo.com
AF: 1. Nuclear Materials Authority, Maadi-Kattamya Road, P.O. Box 530; Maadi, Cairo, Egypt
AU: * Ren, M
EM: ren@geo.utep.edu
AF: 2. Department of Geological Sciences The University of Texas at El Paso , 500 W. University Ave, El Paso, TX 79902, United States
AU: Goodell, P
EM: goodell@geo.utep.edu
AF: 2. Department of Geological Sciences The University of Texas at El Paso , 500 W. University Ave, El Paso, TX 79902, United States
AU: Ragab, A
EM: elsahabi@yahoo.com
AF: 1. Nuclear Materials Authority, Maadi-Kattamya Road, P.O. Box 530; Maadi, Cairo, Egypt
AB: Samples from three locations, Sharm El-Sheikh, Wadi Yahmid, and North Nuweiba area, in southern Sinai, Egypt, have been studied to evaluate them as source rocks for potential uranium deposits. The petrographic and electron microprobe study show that the majority of the rocks are medium grain amphibole alkali feldspar granite and amphibole alkali feldspar quartz syenite. Based on the composition, the amphiboles are mainly the sodic- calcic amphiboles: ferro-barroisite and ferro-richterite. Ferrohedenbergite, biotite, and sphene appears in some samples. The alkali feldspars show perthitic structure with about equal amount of end member orthoclase and albite. The accessory minerals, which are usually included in amphiboles, are zircon, apatite, ilmenite, and magnetite. The major REE accessory phase is chevkinite. The chevkinite usually altered and changed to rutile and thorite in the altered rocks. The two oxide geothermometry give around 700 Celsius degree and oxygen fugacity -18. The reduced condition agrees with the mineral assemblages. The fine grained rocks are mainly amphibole alkali feldspar syenite and amphibole alkali feldspar quartz syenite. The amphibole is the calcic ferro- hornblende, clinopyroxene is ferro-augite. The alkali feldspars are orthoclase and albite; the two feldspars show micrographic texture. The albite has up to 1 percent CaO content. The SiO2 contents of the whole-rock chemistry range from 62 to 77 percent. The agpaitic index are larger than 1. The trace elements show an A-type granite characteristic. The rocks have low Ba, Rb, and Sr; moderately high Zr, Y and REE. The REE pattern show slightly LREE enrichment with low to medium Eu anomaly. The large Eu anomaly rocks show strong alteration. At the same time, the breakdown of amphibole and the chevkinite and zircon which it hosts releases uranium while Ti and Th are left behind. Thus, evolution of uranium source rock in granites is demonstrated by amphibole and accessory mineral alteration studies.
DE: 1065 Major and trace element geochemistry
DE: 3620 Mineral and crystal chemistry (1042)
DE: 3640 Igneous petrology
DE: 3651 Thermobarometry
SC: Volcanology, Geochemistry, and Petrology [V]
MN: 2007 Joint Assembly