GEOLOGY, MINERALOGY, AND GEOCHEMISTRY OF THE DYKES TRAVERSING WADI HAFIYA AREA, EASTERN DESERT, EGYPT

Wadi Hafiya area is dissected by enormous number of dykes and veins of different composition. In the present work only one hundred major dykes were investigated in detail recording their strike, length, width and dip. Also, studying their petrography, opaque mineralogy as well as their geochemistry. The studied dykes are categorized under three groups namely: mafic, intermediate and felsic.
The mafic dykes are represented by basalts and dolerites. They are of three main trends N35°W, N5°E and N85°WE. Their average length is 3.5 km. they generally from negative topography regarding the surrounding host rocks. Petrographically, they show ophitic, sub-ophitic and rare porphyritic texture. Their opaques (about 9% of the rock) are represented by ilmenite, magnetite and pyrite. They were originated from low- to medium-k tholeiitic magma.
The intermediate dykes are represented by andesite and rarely trachy-andesite. They are of two main trends N35°W, N85°E. Their average length is 4.3 km. they show the same topography as the host rocks. Petrographically, they show porphyritic and pilotaxitic textures. Their opaques (about 7% of the rock) are represented by magnetite, ilmenite and pyrrhotite. They were originated from medium- to high-k subalkalic magma.
The felsic dykes are represented by rhyolite, aplite and quartz-feldspar porphyry. They are of three main trends N45°E, N85°E and N45°W. They form prominent ridges with average length 3.6 km.  Their opaques (3%) are mainly represented by ilmenite, magnetite and pyrite. They were originated from high-k subalkalic magma.
From the different characteristics and the cross-cut relationships it is concluded that, these dykes were formed at different periods represented by intrusion of old mafic dykes then the intermediate ones and then the felsic ones and finally other mafic ones.