Colloquim notice
Radiometric Studies of Beach Sands around the Cape Peninsula area of
South Africa
Speaker : Dr. A.K. Mohanty (Physics Group, iThemba LABS)
Date and venue: 2 pm, 13 March 08, iThemba LABS, J-block auditorium
Abstract
The present work focuses on the radiometric characteristics of beach sand deposits
in the Cape Peninsula area of South Africa, to study the provenance characteristics and its
depositional environment based on the radionuclide concentrations. Contrasting
radiometric characteristics were observed in two beach sand deposits from the False Bay
Group (FBG) and West Coast Group (WCG). Relatively higher content of
40
232
Th, 238U and
K concentrations are observed in FBG as compared to the WCG beach sediments. Lower
potassium concentration in the WCG sediments indicates the mineral sand particles were
derived from the sedimentary provinces. The Chi-square (  R2 ) values suggest that, the
distribution of radionuclides are widely scattered in the WCG as compared to FBG.
Transect samples show lateral variations of radionuclides such as thorium and uranium
concentrations, which are gradually increasing, while the potassium concentration
decreases from the shorelines towards the coast. The sedimentary provinces such as Cape
Supergroup and the Table Mountain Group, which occurs in close proximity to the West
Coast, are possible sources for these mineral sands. Based on the Th/U ratio, it is likely
that the beach sediments were deposited in a uranium fixation, and under reducing
conditions.
Keywords: Natural radioactivity; Gamma ray spectrometry, radionuclides, provenance,
beach sand, uranium fixation, west coast