PAN-AFRICAN PLUTONIC SUITE OF UM SHAGHIR AREA, QUSSEIR DISTRICT, EASTERN DESERT, EGYPT: SUBDUCTION ZONE MAGMTISM

Heikal, Mohamed T.S.; El-Naggar, Wifky A.; ElNahas, Atef A.

doi:10.21608/djs.2005.158261

PAN-AFRICAN PLUTONIC SUITE OF UM SHAGHIR AREA, QUSSEIR DISTRICT, EASTERN DESERT, EGYPT: SUBDUCTION ZONE MAGMTISM

Document Type : Research and Reference

Authors

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

² Nuclear Materials Authority, Cairo, Egypt

10.21608/djs.2005.158261

Abstract

The present work deals with the plutonic suite including granitoid gabbro-dioritic rocks at Wadi Um Shaghir area. This suite comprises mappable intrusive bodies of granodiorite-tonalite association in combination with gabbro-diorite complex. No direct contact has been noticed between the two types of rocks.
Geochemically, the granitoids originated from peraluminous calc-alkaline magma with many chemical parameters similar to I-type granites. On the other hands, the studied gabbroids exhibit calc-alkaline nature with chemical characteristics identified to phase I of gabbros described by Heikal et al. (2000). Both types of magmas were developed in an island arc tectonic settins.
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 the weak negative relation between U and K/Rb were obtained.
The granitoids like subduction-related rocks are enriched in LILE and depleted in HFSE suggesting their derivation by partial melting of subarc mantle source region highly metasomatized by aqueous fluids. The abnormally high Ba-content might suggest incorporation of plagic sediments into the melting zone. The dioritic rocks are enriched in both LILS and HFSE suggesting the metasomatizing fluids in the mantle source region were derived from rutile-free subducted slab causing enrichments in HFSE.