Trace Element and Stable Isotope Geochemistry of Lwamondo and Zebediela Kaolins, Limpopo Province, South Africa: Implication for Paleoenvironmental Reconstruction

Abstract

The aim of the present study was the paleoenvironmental reconstruction of the prevailing environment under which the Lwamondo and Zebediela kaolin deposits were formed. Hence, this study reports deuterium and oxygen stable isotope values and trace and rare earth element concentrations for two samples of kaolin. Upper continental crust-normalised trace-element patterns reveal that large ion lithophile elements and high-field-strength elements are generally depleted in Lwamondo and Zebediela kaolins, whereas transition trace elements are generally enriched in these kaolins. Upper continental crust-normalised rare earth element (REE) patterns show that there is a slight enrichment of heavy REEs (HREEs) compared to light REEs (LREEs) in these kaolins. The δ18O and δD stable isotope values for kaolinite from Lwamondo ranged from 17.4‰ to 19.1‰ and from −54‰ to 84‰, respectively, whereas those values for kaolinite from Zebediela varied from 15.6‰ to 17.7‰ and from −61‰ to –68‰ for δ18O and δD, respectively. The REE patterns and the content of other trace elements indicate ongoing kaolinitisation in the Lwamondo and Zebediela kaolins with minimum mineral sorting. The sources of the kaolins varied from basic to acidic and these were derived from an active margin tectonic setting. Lwamondo kaolin was deposited in an oxic environment whereas Zebediela kaolin was deposited under suboxic/anoxic conditions. Based on the δ18O and δD values of the kaolinite, they formed in a supergene environment at temperatures generally below 40 °C.

Genesis and possible applications of Lwamondo and Zebediela Kaolins, Limpopo Province, South Africa

“…However, according to the Köppen-Geiger climate classification, Limpopo Province, where the studied kaolins are found, has an arid steppe hot climate characterised by temperatures above 18°C [43,44]. Previous estimation of the temperature of kaolinisation of studied kaolins showed that the Lwamondo Kaolin formed under temperatures of 26.9 ± 3.6°C, whereas the Zebediela Kaolin formed under temperatures of 36.6 ± 4.2°C [22]. This suggests that in the area, there has been a climatic change from humid when the kaolins formed to arid steppe currently.…”

“…Lwamondo and Zebediela kaolins are in Thulamela and Lepelle-Nkumpi Municipalities in Limpopo Province, South Africa. The geology of Lwamondo and Zebediela areas has been detailed in Raphalalani et al [22]. Lwamondo is mainly dominated by rocks of the Proterozoic Soutpansberg Group [23], whereas Zebediela is made up of rocks of the Proterozoic to Jurassic Transvaal Group [24,25].…”