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 trachy- dacite 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.