Target rocks, impact glasses, and melt rocks from the Lonar impact crater, India: Petrography and geochemistry
Meteoritics and Planetary Science
Department of Geological Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria; National Nuclear Research Institute, Ghana Atomic Energy Commission, P.O. Box LG 80, Legon-Accra, Ghana; Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721 302, India; Geological Survey of India, 27 Jawaharlal Nehru Road, Kolkata 700016, India
The Lonar crater, India, is the only well-preserved simple crater on Earth in continental flood basalts; it is excavated in the Deccan trap basalts of Cretaceous-Tertiary age. A representative set of target basalts, including the basalt flows excavated by the crater, and a variety of impact breccias and impact glasses, were analyzed for their major and trace element compositions. Impact glasses and breccias were found inside and outside the crater rim in a variety of morphological forms and shapes. Comparable geochemical patterns of immobile elements (e.g., REEs) for glass, melt rock and basalt indicates minimal fractionation between the target rocks and the impactites. We found only little indication of post-impact hydrothermal alteration in terms of volatile trace element changes. No clear indication of an extraterrestrial component was found in any of our breccias and impact glasses, indicating either a low level of contamination, or a non-chondritic or otherwise iridium-poor impactor. © The Meteoritical Society, 2005.
crater; glass; impact structure; melt; shock metamorphism; Asia; Eurasia; India; Lonar Crater; Maharashtra; South Asia