Bosumtwi impact structure, Ghana: Geochemistry of impactites and target rocks, and search for a meteoritic component

available online at http://meteoritics.org 1493 © The Meteoritical Society, 2005. Printed in USA. Bosumtwi impact structure, Ghana: Geochemistry of impactites and target rocks, and search for a meteoritic component Xiongxin DAI1, 4, Daniel BOAMAH1, Christian KOEBERL1*, Wolf Uwe REIMOLD2, Gordon IRVINE3, and Iain MCDONALD3 1Department of Geological Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria 2Impact Cratering Research Group, School of Geosciences, University of the Witwatersrand, P. O. Wits, Johannesburg 2050, South Africa 3Department of Earth Sciences, Cardiff University, P.O. Box 914, Cardiff CF10 3YE, United Kingdom 4Current address: Department of Physics, Queen’s University, Stirling Hall, Queen’s Crescent, Kingston, Ontario K7L 3N6, Canada *Corresponding author. E-mail: [email protected] (Received 20 January 2005; revision accepted 13 July 2005) Abstract–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.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.