RELATION BETWEEN MINERALOGY, GEOCHEMISTRY AND DURABILITY OF SOME ALKALINE ROCKS, SOUTH EASTERN DESERT, EGYPT

The use of mineralogical characteristics, chemical analysis and mechanical characteristics in addressing the behavior of some alkaline rocks to resist weathering action is discussed in the present research paper. The alkaline rocks outcropping at two selected areas in the southern Eastern Desert, namely Hamrat Salma and Abu Khrug are studied. Field relation, petrography and chemical analysis of the rocks in areas, durability and unconfined compressive strength were done. Durability and unconfined compressive strength tests evaluate the resistance of the studied alkaline rocks to natural weathering. The studied alkaline rocks in both areas are classified mineralogically and chemically as trachyte, and syenite. In Hamrat Salma, the alkaline rocks are represented by trachyte, whereas in Abu Khrug area, they are discriminated to trachydacite and syenite. All the studied alkaline rocks have alkaline affinity and emplaced in anorogenic tectonic regime. The results of compressive strength and durability of Hamrat Salma trachyte and Abu Khrug syenite showed very strong strength. The lowest value was obtained from syenite with xenoliths and trachyte of Abu Khrug showing medium strength. Negative relation between uniaxial compressive strength and durability is recorded. The existence of xenoliths, veins and porphyritic texture create a weak relationship. There is a linear relationship between compressive strength and some major oxides (SiO2, Al2O3 and Na2O) for the rock types. Also, a direct relation between durability and (Fe2O3, K2O) was recorded.