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Abstract
The present study deals with the factors controlling the distribution of uranium, thorium and other elements in some shear zones of selected younger granites, south Sinai, Egypt.Four areas are selected for this purpose namely El-Regita, Ghazala, El-Rosis and Um Zeriq shear zones.
El-Rosis area is located to the southeast of the Katherina city and can be reached via Wadi Isbaiya while El-Regita area is located to the northeast of the Katherina Mountain and can be reached through Wadi El-Sheikh. Wadi Ghazala area is located in the southeastern part of Sinai Peninsula, and can be accessed through Wadi Watir while Wadi Um Zariq can be reached through Wadi El-Saada southwest Nuweiba city
The field and petrographic studies declare that El-Regita area is mainly covered by granodiorite and monzogranite where they intrude the neighboring rocks with sharp contacts. The monzogranite is medium to coarse-grained with pinkish colour and shows hypidiomorphic, myrmekitic and perthitic textures. It is mainly composed of potash feldspars, quartz and plagioclase, biotite and muscovite are present in lesser amount, while zircon, apatite and sphene are the accessory minerals.
Two important shear zones are observed in the monzogranite of El-Regita area, namely El-Regita shear zone and the pegmatite shear zone. The trend of the former one is nearly N 70o W and has dimensions 600m X 3m. Cu-quartz stockworks are developed along this shear zone and mainly associated with argillic alteration, hematization and the presence of clay minerals and kaolinite. The intersection of this shear zone with a doleritic dyke is marked by an enrichement of bluish and greenish copper minerals present as stockworks. Away from the doleritic dyke, hematitized spots are observed to contain cavities filled with calcite and highly radioactive canarian-yellow minerals. The pegmatite shear zone trends N 80o W and cutting through a zoned pegmatite body. Hematitization, kaolinization and high radioactive black mineral can be detected along the fracture system developed through the fissure and fault planes of shear zone along the zoned pegmatite.
El-Rosis area is mainly covered by granodiorite, syenogranite and alkali feldspar granite. The granodiorite is medium to coarse grained and exhibits granular hypidiomorphic texture. It consists essentially of plagioclase, K-feldspar, quartz, biotite, chlorite and/or hornblende. Epidote, sphene, apatite, zircon and iron oxides are accessories. Sericite, kaolinite and chlorite are secondary minerals. The syenogranite is composed essentially of quartz, alkali feldspar and plagioclase, with biotite, and accessories of iron oxides, zircon and apatite. The alkali-feldspar granite consists mainly of K-feldspar, quartz, plagioclase, muscovite and biotite. Zircon and apatite are accessories while chlorite, iron oxide and sericite are secondary The mineralized shear zone of El-Rosis area are included within the alkali feldspar granites and has N 60-70 W trend and show alteration products such as silicification, hematitization and kaolinization. Magnetite and Cu-minerals are generally associated with yellow coloured secondary uranium minerals present as cavity fillings. br>Ghazala area is mainly covered by highly jointed (NE-SW and NW-SE) monzogranite and syenogranite.