This thesis reports the results of a mineralogical and geochemical study of pans situated in the
Northern Cape Province with special emphasis on the clay minerals. From east to west the
depth and size of the pans increase and associated with this increased maturity the abundance
of salt (halite and thenardite) and the quantity of green sediment are also enhanced.
Chemically the sediments are dominated by SiO2 that also dilutes Fe2O3, K2O, Na2O, Al2O3
and MgO (when associated with dolomite) concentrations. Authigenic calcite, dolomite,
analcime and loughlinite (Na-sepiolite) occur in some of the pans to the west and FTIR
spectrometry indicates that all the pans host glauconite and/or celadonite. However, smectite,
illite/smectite interstratification, kaolinite and/or chlorite and loughlinite only occur in some
pans. The glauconite and/or celadonite does not occur as discrete mineral grains, but forms
part of the fine-grained matrix common to all of the pans and no evidence of any precursor
minerals were observed. The pan environment appears to present a closed, saline setting that
is conducive for the direct precipitation of a mica with a chemical composition between that
of glauconite and celadonite. The influence of the water-table on the formation of the
glauconite and/or celadonite appears to be significant, as the highest abundance of salt is
invariably associated with the position in the profile where the sediment appears to reach its
most intense green colour. In the case of Koi Pan, the celadonite component of the solid
solution seems to increase as the green colour intensifies. Loughlinite in Koi Pan and Brak
Pan sediments also appear to be authigenic and it is suggested that it forms after precipitation
of low Mg calcite that leads to Mg enrichment of the system and consequent sepiolite
formation associated with minor dolomite. Thermoluminescence ages obtained from the Koi
Pan sediment range between 37ka and 48ka before present at a depth of ~120cm below the
surface, while for Brak Pan, at roughly the same depth, an age of between 110ka and older
than 150ka before present was obtained. This may suggest different sedimentation rates in the
pans or much younger ages and thus faster formation of glauconite and/or celadonite in Koi
Pan since it is suggested that the mineral is authigenic. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2010.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/5355 |
| Date | January 2010 |
| Creators | Roelofse, Tiani. |
| Contributors | Cloete, M., Dunlevey, J. M. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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