GEOMORPHOLOGY, CHARACTERISTICS AND MINERALOGY OF SOME SOILS IN EL-FARAFRA OASIS, NEW VALLEY GOVERNORATE, EGYPT

The studied area belongs to El-Farafra Oasis, New Valley Governorate. It is representing an area of about 372062 feddans. The aim of this work was to study the geomorphology, characteristics and mineralogy of some soils in El-Farafra Oasis, New Valley governorate, Egypt. Visual interpretation of 2 sentinel images and digital elevation model (DEM) were used to produce the geomorphic units and soil maps of the studied area. Two geomorphic units were identified namely plateau and depression floor. Eighty-two minipits and eighteen soil profiles were chosen to represent the main soil mapping units in the studied area. Soil samples were collected from the representative soil profiles for physical, chemical and mineralogical analysis. The results could be summarized as follows: X-ray diffraction analysis indicated that kaolinite is alternatively dominated in the studied soils (about 80 %) followed by smectite. Illite, interstratified minerals and chlorite are found as the lowest abundant clay minerals in these soils. The mineralogical composition of the sand fraction indicated that, the light fraction is composed almost entirely of quartz which constitutes about 95%. Feldspar minerals (orthoclase plagioclase and microcline) are detected in trace amounts. The presence of feldspars indicates that, the soils are young from the pedological point of views. Heavy minerals are generally dominated by opaque’s (about 55 %). Non-opaques are mainly dominated by pyroboles (pyroxenes + amphipoles) followed by ultra-stable minerals (zircon, rutile and tourmaline), Para metamorphic minerals (garnet, kyanite, staurolite, silimanite) and epidote. While the other minerals (biotite andalusite, glaucohite and apatite) are detected in less pronounced amounts. Distribution of the resistant minerals (biotite and amphipoles) weathering ratio, values indicate that, the soils are generally heterogeneous either due to their multi-origin or due to a subsequent variation along the course formation.