The mineralogical and geochemical study of the Etosha meteorite from the North-West University collection

Abstract

The Etosha meteorite, which is part of the North-West University (NWU) collection, was found in 1970 in the Etosha National Park in Namibia. Although the meteorite has been described by previous researchers, its re-evaluation was crucial so as to be able to update the mineralogy, geochemistry and classification concerned, using modern analytical techniques. Meteorite geochemistry is very important, as it assists in understanding our solar system, which should lead to the expansion of knowledge regarding the previous and future biological and chemical evolutions that have taken place on Earth. Furthermore, the classification of meteorites is also crucial, as it enables the grouping of meteorites, and facilitates the associated understanding and description. Polished sections of the Etosha meteorite were prepared and analysed, so as to be able to determine (1) the mineralogy and geochemistry through X-ray diffraction (XRD), portable X-ray fluorescence (pXRF) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS); (2) the petrographic characteristics through reflected light microscopy; and (3) the mineral chemistry through electron probe microanalysis (EPMA), as well as the classification of the Etosha meteorite. The results obtained in this study show that the Etosha meteorite contains 85-89 wt. % Fe, 5-7,8 wt. %Ni with minor amounts (± 9 wt. %) of P, Co, Cu, Cr, S and other elements. The Etosha meteorite is comprised of kamacite (α-FeNi), taenite (ɣ-FeNi), cohenite (Fe3C), schreibersite ((Fe,Ni)3P) , rhabdite ((Fe,Ni)3P), magnetite (Fe3O4) and a possible iron phosphate. The average kamacite bandwidth is approximately 2,35 mm, classifying the meteorite as a coarse octahedrite, which does not correspond with the findings made in previous studies that classified it as a medium octahedrite. The Ga (57,01 ppm), Ge (189,77 ppm) and Ni concentrations classified the Etosha meteorite chemically as an IIAB iron meteorite. Sub-Saharan Africa hosts many different meteorites, with the majority of meteorite discoveries having occurred in the north-western, southern and eastern parts of the region. The total mass per country, as well as the number of finds made, corresponds with this trend. Chondrites are the most common meteorite discovered, with achondrites, irons and stony-irons being second, third and fourth most common, respectively speaking. The Etosha meteorite was identified as one of eight IIAB iron meteorites found in the region, with three of the meteorites being discovered in Southern Africa, with the closest to the Etosha meteorite being the Okahandja meteorite (Namibia), with two meteorites having been discovered in South Africa, namely the Kopjes Vlei meteorite and the Hex River Mountains meteorite.