Reevaluating the impact origin of the Luna Structure in western India using mineralogy, highly siderophile elements, and Re‐Os isotopes

Abstract The Holocene Luna Structure in western India has been claimed to be the fourth and youngest impact crater on the Indian subcontinent. The circular shape; the unusual mineralogy including high‐temperature mineral phases such as kirschsteinite and wüstite; and the elevated abundance of highly siderophile elements (HSE: Os, Ir, Ru, Rh, Pt, and Pd) have been provided as evidence in favor of an impact origin. Here, we present new mineralogical, bulk rock geochemical data including isotope‐dilution HSE abundances and 187 Re‐ 187 Os compositions of the suspected Luna impactites. The samples are dense irregular nodules with undulated surface and flow‐like structures and are glassy to extremely fine grained, with or without vesicles. The new HSE data show no Ir enrichment compared to upper continental crust. The radiogenic measured 187 Os/ 188 Os compositions (0.2289–0.7253) further rule out any extraterrestrial contribution in the suspected impactites. The observed high‐temperature mineral assemblage shows similarity to that of iron‐rich archaeological slags. We reinterpret the Luna Structure materials as slags that are likely associated with the Bronze Age in the Harappan Civilization and may have formed as a byproduct of copper smelting. Considering the new evidence, the Luna Structure of western India is not a meteorite impact crater.