GEOLOGY AND PETROLOGY OF ABU DURBA-ABU HASWA GRANITOID ROCKS, SOUTHEASTERN SINI, EGYPT

Anbar, Mohamed M.; El-Naggar, Wifky S. A.; El Nahas, Atef A.; Darwish, Mostafa M.

doi:10.21608/djs.2005.158267

GEOLOGY AND PETROLOGY OF ABU DURBA-ABU HASWA GRANITOID ROCKS, SOUTHEASTERN SINI, EGYPT

Document Type : Research and Reference

Authors

¹ Geology Dept., Fac. Sci.,Tanta Univ., Egypt

² Nuclear Materials Authority, Cairo, Egypt

10.21608/djs.2005.158267

Abstract

The present work deals with the plutonic suite of Gabal Abu Durba-Gabal Abu Haswa area in the southwestern part of Sinai along the Gulf of Suez. It comprise an elongate granitoid belt covering collectively about 35km² and trending NW. this suite comprises two phases of granitoids where phase II younger granites (granodiorites) and phase III (monzogranite and alkali feldspar granite), intruded into dacite, rhyodacite, rhyolite and equivalent pyroclastics of the Dokhan volcanic type.
Geochemically, the granitoids of Gabal Abu Durba-Gabal-Abu Hasw area seem to have originated from metaluminous to peraluminous calc-alkaline magmas with many chemical features similar to I-type granites.
The granitoiditic magmas were developed in an island arc tectonic setting whears the granitic ones were developed in a within-plate tectonic setting. The studied granitoids were generated at somewhat intermediate depths (9-21 km) equivalent to 3-7 kb under temperature ranging from 760°-840°. This is consistent with the high k/Rb ratios, and the low k/Ba ratios indicate involvement of ocean sediments in magma generation.
The concentrations of U and Th in the granitoid rocks were controlled by magmatic processes which are clear from the positive relation between U and Th and U-Zr in addition to weak negative relation between U and k/Rb observed. They are also controlled by the presence of some accessory minerals (zircon and apatite) and iron oxides. Iron oxides and hydroxides are known to absorb U from circulating fluids.