Bosumtwi impact structure, Ghana: Geochemistry of impactites and target rocks, and search for a meteoritic component
Meteoritics and Planetary Science
Department of Geological Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria; Impact Cratering Research Group, School of Geosciences, University of the Witwatersrand, P.O. Wits, Johannesburg 2050, South Africa; Department of Earth Sciences, Cardiff University, P.O. Box 914, Cardiff CF10 3YE, United Kingdom; Department of Physics, Queen's University, Stirling Hall, Kingston, Ont. K7L 3N6, Canada
Major and trace element data, including platinum group element abundances, of representative impactites and target rocks from the crater rim and environs of the Bosumtwi impact structure, Ghana, have been investigated for the possible presence of a meteoritic component in impact-related rocks. A comparison of chemical data for Bosumtwi target rocks and impactites with those for Ivory Coast tektites and microtektites supports the interpretation that the Bosumtwi structure and Ivory Coast tektites formed during the same impact event. High siderophile element contents (compared to average upper crustal abundances) were determined for target rocks as well as for impactites. Chondrite-normalized (and iron meteorite-normalized) abundances for target rocks and impactites are similar. They do not, however, allow the unambiguous detection of the presence, or identification of the type, of a meteoritic component in the impactites. The indigenous siderophile element contents are high and possibly related to regional gold mineralization, although mineralized samples from the general region show somewhat different platinum-group element abundance patterns compared to the rocks at Bosumtwi. The present data underline the necessity of extensive target rock analyses at Bosumtwi, and at impact structures in general, before making any conclusions regarding the presence of a meteoritic component in impactites. © The Meteoritical Society, 2005.
crater; impact structure; impactite; meteorite; shock metamorphism