Zhamanshin astrobleme provides evidence for carbonaceous chondrite and post-impact exchange between ejecta and Earth's atmosphere.

ABSTRACT: Chemical fingerprints of impacts are usually compromised by extreme conditions in the impact plume, and the contribution of projectile matter to impactites does not often exceed a fraction of per cent. Here we use chromium and oxygen isotopes to identify the impactor and impact-plume processes for Zhamanshin astrobleme, Kazakhstan. ε⁵⁴Cr values up to 1.54 in irghizites, part of the fallback ejecta, represent the ⁵⁴Cr-rich extremity of the Solar System range and suggest a CI-like chondrite impactor. Δ¹⁷O values as low as -0.22‰ in irghizites, however, are incompatible with a CI-like impactor. We suggest that the observed ¹⁷O depletion in irghizites relative to the terrestrial range is caused by partial isotope exchange with atmospheric oxygen (Δ

SUBMITTER: Magna T 

PROVIDER: S-EPMC5550458 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature