Mineralogical Appraisal of Sediments of Duricrust Suites and Pans around Jwaneng Area, Botswana|
Atlhopheng, Julius R. & Ekosse, Georges-Ivo E.
A mineralogical investigation of duricrust suites in Letlhakeng valley, and five pans around
Jwaneng in Botswana was undertaken in order to know the mineral assemblages and infer on their landscape
formation. In Letlhakeng, duricrusts comprised calcretes, silcretes and ferricretes. Calcretes were dominated by the
minerals: calcite, quartz and to a lesser extent dolomite. Silcrete mineralogy was dominated by quartz, opal, and
some occurrences of palygorskite, microcline and rutile. The intermediate forms of cal-silcretes yielded quartz,
muscovite, and kaolinite. Ferricretes occurred on an area of the valley capping, with minerals dominated by
goethite and haematite. The indurates are believed to have been formed through groundwater mechanisms. The
general lowering of the valley, led to precipitation of the duricrusts. The pans were dominated by calcrete and
silcrete only. The calcretes mineralogy was mainly calcite, dolomite and quartz. Illite-montmorillonite and
sepiollite were also present. Samples of pan clay floor, other than being dominated by calcite, dolomite and quartz,
also had sepiollite ferrian. Pans and valleys are accumulation sites, with polygenetic modes of genesis. The
duricrusts have undergone several alterations throughout time.