Mineralogical and geochemical studies of impact melt products from the Chesapeake Bay and the Lake Bosumtwi impact structures (ICDP)

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ICDP performed two successful core drilling projects into (i) the Lake Bosumtwi impact structure (1.07 Ma old, Ø~10.5 km), Ghana, and (ii) together with USGS, the Chesapeake Bay impact structure, Virginia (35 Ma, Ø~80 km). Both excellently preserved craters belong to only four known craters associated with microtektite and tektite strewn fields. This proposal focuses on melt products that originated in these impact events. Our geochemical and mineralogical studies on tektites, microtektites, glass shards in breccias and fallback spherules, an extremely rare glass product, aim at ● Identification of precursor materials and degree of chemical homogenization of glasses (TEM-EDX, LAICP-MS); ● Constraining processes that yield different types of melts; ● Unraveling mixing processes, high-temperature chemistry and redox conditions in vapor plume (using EELS for valence state determination of iron); ● Deciphering the different cooling paths of impact glasses. Our new data contribute to a better understanding of cratering, serve as input parameters for numerical modeling and provide tools to distinguish microtektites from volcanic glass spherules – a point of particular relevance for the interpretation of Archean spherule layers.