MINERALOGY OF THE SAND FRACTION AND ITS BEARING ON SOIL GENESIS AND FORMATION OF WADI EL-NATROUN DEPRESSION SOILS, WESTERN DESERT, EGYPT

The objective of the current work is to identify the mineralogical composition of the sand fraction of wadi El-Natroun Depression soils in order to evaluate the genesis and degree of homogeneity of soils of the study area.

Landsat ETM+ image (2018) and digital elevation model (DEM) were used in Arc 10.8 software to produce the geomorphic map of wadi El-Natroun area. The landscapes include four units i.e table land, wadi terraces, wadi depression and alluvial plain. Fifteen soil profiles were selected to represent the main geomorphic units. Soil samples have been collected for mineralogical analysis.

The obtained results indicate that the mineralogical composition of the sand fraction consists of light and heavy minerals. The light minerals are the major component and mainly dominated by quartz which constitutes more than 90%. Normal quartz grains with homogenous straight extinction are common indication acidic plutonic parent rocks (mainly granitic rocks).

The other members of light fraction are feldspars (orthoclase and plagioclase series), mica (muscovite) and few calcite. The heavy-minerals are composed of opaque and non-opaque minerals. Opaque minerals are generally the major heavy fractions constituent in all the examined soils. These minerals are essentially composed of iron oxide minerals (e.g. magnetite, illimanite and hematite). The ultra stable minerals (zircon, rutile and tourmaline) mainly dominate the non-opaque minerals followed by igneous minerals (amphiboles, pyroxenes and epidotes). However, the metamorphic minerals (granite, kyanite, staurolite, sillimanite, and andalusite) are detector in considerable portions. This suggests that the studied soils are still young, poorly developed and immature from pedological point of view.

The heavy minerals distribution show that Wadi El-Natroun area is receiving sediments derived from mixture of two important provenances, the first is dominated by sedimentary rocks, and the second provenance is dominated by igneous and metamorphic.