Definition
Iridium is a hard, brittle, corrosion-resistant metal with the symbol 77Ir. It is one of the platinum group elements (or PGE) – ruthenium, rhodium, palladium, rhenium, osmium, iridium, and platinum – which are highly siderophilic and form strong bonds with iron. Most of the terrestrial PGE are concentrated in the core, leaving the mantle and crust highly depleted in Ir (ca. 3 and < 0.05 ppb, respectively). In comparison, undifferentiated meteorites (meteorites that have not suffered geological evolution) are enriched in PGE (ca. 200–500 ppb). Elevated PGE concentrations measured in terrestrial rocks can indicate a meteoritic contribution. The detection of the iridium enrichment in the KT Or K-Pg boundary clay layer first found in Gubbio, Italy, and then confirmed all over the world, led to the meteoritic impact hypothesis as a possible cause of the dinosaur extinction. The determination of PGE elemental ratios in impactites can contribute to the identification of the type...
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Claeys, P. (2022). Iridium. In: Gargaud, M., et al. Encyclopedia of Astrobiology. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-27833-4_808-4
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DOI: https://doi.org/10.1007/978-3-642-27833-4_808-4
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