Platinum group elements in the ICDP cores from the Bosumtwi crater, Ghana

Introduction: The Bosumtwi crater has a diameter of 10.5 km and is located in the center of Ghana in West Africa (6o 30’ N and 1o 25’ W). Its age is 1.05 Ma and it forms a well preserved impact structure with a well defined rim. Its center is occupied by the closed basin of Lake Bosumtwi. The target rock is essentially composed of Proterozoic (2.1 to 2.2 Ga) units of the Birimian Supergroup that consists of lower greenschist facies metasediments, schists, phyllites, graywackes, quartzite and a minor granitic component. The Bosumtwi crater is the probable source of the Ivory Coast tektites and microtektites recovered from drillings in the East Tropical Atlantic [1]. The Bosumtwi crater was drilled in the Summer and Fall of 2004 by the International Scientific Drilling Project (ICDP) [2]. Two cored holes (LBO7A and LBO7B) located in the crater center (Fig. 1) penetrated through the lake sediments into impactite lithologies. The goal of this study was to identify the type of projectile responsible for the formation of the Bosumtwi crater based on PGE elemental ratios [3].