Crater-fill impact breccia and basement rock samples from the 1.07 Ma Bosumtwi impact structure (Ghana) were recovered for the first time in 2004 during an International Continental Scientific Drilling Program (ICDP)–sponsored drilling project. Here, we present detailed results of major- and trace-element analyses of 119 samples from drill core LB-08A, together with the chemical compositions of melt particles from suevite. The meta-graywacke and phyllite/slate crater basement rocks can be easily distinguished from each other on the basis of their bulk chemical compositions. A comparison of the chemical compositions of crater-fill and fallout suevites, as well as between proximal and distal impactites, reveals that LB-08A suevites have higher MgO, CaO, and Na 2 O contents than fallout suevites and, similarly, that the CaO and Na 2 O contents are higher by a factor of approximately two in LB-08A suevites than in Ivory Coast tektites. Noticeable differences occur in Cr, Co, and Ni contents between the different impactites; higher abundances are observed for these elements in distal impactites. The observed differences in composition in the various impactites mainly reflect mixing of different proportions of the original target lithologies, as can be seen in the differences in the clast populations between crater-fill and fallout suevites. However, the original impactite compositions may have also been modified by postimpact alteration, particularly in the proximal impactites. Melt particles in suevite show significant differences in major-element compositions between the different samples investigated, but also within a given sample, indicating that they represent melts derived from different lithologies.

The ca. 2.45 Ga pyritic uraniferous quartz-pebble conglomerate (UQC) of the Matinenda Formation of the Elliot Lake Group, Huronian Supergroup, was used in this study to investigate the origin of pyrite. A laser-microprobe was used for analysis of the sulfur isotopic compositions of individual pyrite grains, and an electron-probe microanalyzer was used for analysis of the trace element compositions of pyrite grains with overgrowth texture. We found a variation in δ 34 S values among pyrite crystals (73 analyses) of various size and morphologies that occur in a small (∼1 cm 3 ) rock chip: the total range in δ 34 S is −9.0‰ to +5.5‰ with respect to CDT (Cañon Diablo Troilite) with a mean value of +0.6‰ ±2.1‰ (1σ). The widest range of ∼15‰ is found among euhedral pyrite grains whereas variations of ∼4‰ to ∼6‰ are common in anhedral, subhedral, and rounded grains of pyrite. These values are in marked contrast to the δ 34 S values of pyrite from the Matinenda Formation that were obtained by previous investigators using bulk-rock sulfur isotope analyses. We found variable concentrations of Co (below detection to 4700 ppm), Ni (to 1900 ppm), and As (to 3400 ppm) among individual pyrite crystals and within single grains with overgrowth textures. These elemental concentrations are markedly different between core and overgrowth parts of pyrite. We demonstrate that the pyrite grains in the Paleoproterozoic UQC have been isotopically, chemically, and morphologically modified by post-depositional processes, suggesting that the pyrite grains have undergone multiple generations. The results of the present study cannot be explained solely by a detrital process. Therefore, one cannot use the preserved morphology and chemistry of pyrite (and possibly uraninite) to represent the original features at the time of deposition to support the hypothesis of an anoxic atmosphere prior to 2.2 Ga.