MINERALOGICAL CHARACTERIZATION OF SOILS REPRESENTING THE CLAY PLAIN OF SUDAN

Abstract

Soil profiles were dug in the clay plains of Sudan and six profiles were selected in a transect from East of
Rahad River, across Gezira, and west of the White Nile. The objectives of this study were to investigate
the clay mineralogical characteristics of these soils, mineralogical forms and soil samples according to
genetic horizons. Twenty four soil samples and four genetic horizons were selected from the six soil
profiles; and were selected for identification of clay mineralogy by X-ray diffraction technique (clay
fraction method). The analysis of clay minerals was performed in two steps; the first step was the
separation of less than 2µ clay size fraction and the second step was the X-ray technique itself. Results on
mineralogical investigations for the primary clay revealed high content of quartz, and muscovite which
were also observed in the clay fraction of the soils. Proportions of smectite, kaolinite with relatively
higher values of smectite especially in the sub-soils were recorded, Illite and chlorite was lower. Part of
the White Nile and the remaining soils have been derived from the Ethiopian plateau which is dominated
by basic and ultra basic rocks; these rocks are dominant in smectite clays. Quartz, Muscovite and Illite are
the main primary minerals in the studied soils with minor amounts of Zeolite, Pyroxene and Calcite
minerals. The clay minerals showed Smectite, Kaolinite, Illite and Chlorite in variable amounts. From the
above results, we can conclude that the identified clay minerals in the studied soils are detrital and
originated from the Ethiopian Plateau and later on have mixed with limestone material during
transportation