Mineralogy of Saudi Arabian Soils: Eastern Region

Abstract

Mineralogical properties of soils along a 500 km east-west transect of an eastern province of Saudi Arabia were examined. Mineralogical composition of soils along the eastern coastal playa near Al Qatif is mostly gypsum or calcite in the whole soil, and smectite among layer silicate minerals in the clay fraction (< 2µm). In soils of the Harad area palygorskite and smectite are the major layer silicate minerals. In the Al Kharj area kaolinite and smectite are the major clay minerals. Small amounts of chlorite occur in all soils studied although it varies in thermal stability and the amount is very small in Al Kharj 11 and Al Kharj Mountain surface soils. In the entire eastern region mica and vermiculite are present in the soil clays. The results of transmission electron microscopy and x-ray diffraction analyses show that acicular palygorskite is widely distributed in the eastern-region soils. Palygorskite is believed to originate from the underlying Mio-Pliocene limestone in the basin, and to be redistributed by alluvial and eolian processes.