MINERALOGICAL STUDIES ON CLAY AND SAND FRACTIONS AS WELL AS HOMOGENEITY OF SOILS IN SOUTH TUSHKA AREA, EGYPT

Abstract

The present work was carried out to study the mineralogical composition of the clay and sand fractions of some soils located at Tushka area between Latitudes 22 o 00 \ and 23 o 28 \ N, and longitudes 30 o 00 \ and 32 o 00 E. To fulfill this objective Landsat 8 image and digital elevation model (DEM) of the studied area were used to define the geomorphic units of the studied area. The geomorphic units of the area under consideration could be grouped and described as Young Alluvial Plain, Old alluvial Plains, Pedi Plain, Playa and Aeolian Plain. The different geomorphic units were represented by 26 soil profiles. The obtained results indicate that, the studied soils are dominated by Kaolinite clay mineral followed by montmorillonite, interstratified minerals and illites. Also, chlorite minerals are presented in variable frequency depending on the parent material of these soils. The minerals assemblage are interpreted in terms of lithology and depositional environments. The mode of formation of the pre-wet climatic condition is in contrast to the present aridity status. Mineralogical composition of the sand fraction showed that, light minerals are the major component and mainly dominated by quartz which constitutes more them 89%. Feldspars are depicted with a few amounts not exceed 11% and represented by plagioclase, orthoclase and microcline. On the other hand, heavy minerals are dominated by opaques which constitute from 33% to 60.3%. Non-opaque minerals are dominated by pyroboles (pyroxene + Amphiboles,) followed by very stable minerals (Zircon, rutile and tourmaline). Slightly stable minerals (garnet and epidote) and stable minerals (staurolite, kyanite, silimanite and andalusite) are found in less pronounced amounts. The frequency distribution of very stable minerals (Zircon, rutile and tourmaline) and weathering ratios lead to conclusion that, the studied soils are heterogeneous either due to their multi-origin and\ or multi-depositional regimes.