IRIDIUM METAL IN CHICXULUB IMPACT MELT - FORENSIC CHEMISTRY ON THE K-T SMOKING GUN

Iridium concentrations in successively smaller subsplits of melt rock and melt breccia from the Chicxulub impact basin were tracked to isola te and identify iridium carrier phases. Iridium-rich particles were is olated from two samples, and a micrometer-scale, silicate-enclosed agg regate of subhedral iridium metal grains was identified in one, confir ming earlier reports of iridium at ground zero of the impact at the Cr etaceous-Tertiary (K-T) boundary. The aggregate may be either a phase formed after the collision or a relict of the Chicxulub basin-forming meteorite. In either case, its presence indicates that even among the largest impact structures on Earth, meteoritic components may be prese rved within the crater.