Target rocks, impact glasses, and melt rocks from the Lonar crater, India

Author(s)

Toni Schulz, Ambre Luguet, Wencke Wegner, David van Acken, Christian Koeberl

Abstract

The Lonar crater is a ~0.57-Myr-old impact structure located in the Deccan Traps of the Indian peninsula. It probably represents the best-preserved impact structure hosted in continental flood basalts, providing unique opportunities to study processes of impact cratering in basaltic targets. Here we present highly siderophile element (HSE) abundances and Sr-Nd and Os isotope data for target basalts and impactites (impact glasses and impact melt rocks) from the Lonar area. These tools may enable us to better constrain the interplay of a variety of impact-related processes such as mixing, volatilization, and contamination. Strontium and Nd isotopic compositions of impactites confirm and extend earlier suggestions about the incorporation of ancient basement rocks in Lonar impactites. In the Re-Os isochron plot, target basalts exhibit considerable scatter around a 65.6 Myr Re-Os reference isochron, most likely reflecting weathering and/or magma replenishment processes. Most impactites plot at distinctly lower

¹⁸⁷Re/

¹⁸⁸Os and

¹⁸⁷Os/

¹⁸⁸Os ratios compared to the target rocks and exhibit up to two orders of magnitude higher abundances of Ir, Os, and Ru. Moreover, the impactites show near-chondritic interelement ratios of HSE. We interpret our results in terms of an addition of up to 0.03% of a chondritc component to most impact glasses and impact melt rocks. The magnitude of the admixture is significantly lower than the earlier reported 12–20 wt% of extraterrestrial component for Lonar impact spherules, reflecting the typical difference in the distribution of projectile component between impact glass spherules and bulk impactites.

Organisation(s)

Department of Lithospheric Research

External organisation(s)

Rheinische Friedrich-Wilhelms-Universität Bonn, Naturhistorisches Museum Wien (NHM)

Journal

Meteoritics and Planetary Science

Volume

51

Pages

1323-1339

No. of pages

17

ISSN

1086-9379

DOI

https://doi.org/10.1111/maps.12665

Publication date

07-2016

Peer reviewed

Yes

Austrian Fields of Science 2012

105105 Geochemistry

Keywords

ASJC Scopus subject areas

Geophysics, Space and Planetary Science

Portal url

https://ucrisportal.univie.ac.at/en/publications/9f4ee29a-0940-4f96-9483-b958a512f5f9