Cosmogenic radionuclides and mineralogical properties of the Chelyabinsk (LL5) meteorite: What do we learn about the meteoroid?

Autor(en)

Pavel P. Povinec, M. Laubenstein, Timothy A. J. Jull, Ludovic Ferriere, F. Brandstaetter, I. Sykora, Masarik J., A. Kovacik, Daniel M Topa, Christian Koeberl

Abstrakt

On February 15, 2013, after the observation of a brilliant fireball and a spectacular airburst over the southern Ural region (Russia), thousands of stones fell and were rapidly recovered, bringing some extremely fresh material for scientific investigations. We undertook a multidisciplinary study of a dozen stones of the Chelyabinsk meteorite, including petrographic and microprobe investigations to unravel intrinsic characteristics of this meteorite. We also study the short and long-lived cosmogenic radionuclides to characterize the initial meteoroid size and exposure age. Petrographic observations, as well as the mineral compositions obtained by electron microprobe analyses, allow us to confirm the classification of the Chelyabinsk meteorite as an LL5 chondrite. The fragments studied, a few of which are impact melt rocks, contain abundant shock melt veins and melt pockets. It is likely that the catastrophic explosion and fragmentation of the Chelyabinsk meteoroid into thousands of stones was in part determined by the initial state of the meteoroid. The radionuclide results obtained show a wide range of concentrations of

¹⁴C,

²²Na,

²⁶Al,

⁵⁴Mn,

⁵⁷Co,

⁵⁸Co, and

⁶⁰Co, which indicate that the pre-atmospheric object had a radius >5 m, consistent with other size estimates based on the magnitude of the airburst caused by the atmospheric entry and breakup of the Chelyabinsk meteoroid. Considering the observed

²⁶Al activities of the investigated samples, Monte Carlo simulations, and taking into account the

²⁶Al half-life (0.717 Myr), the cosmic-ray exposure age of the Chelyabinsk meteorite is estimated to be 1.2 ± 0.2 Myr. In contrast to the other radionuclides,

¹⁴C showed a very large range only consistent with most samples having been exposed to anthropogenic sources of

¹⁴C, which we associate with radioactive contamination of the Chelyabinsk region by past nuclear accidents and waste disposal, which has also been confirmed by elevated levels of anthropogenic

¹³⁷Cs and primordial

⁴⁰K in some of the Chelyabinsk fragments.

Organisation(en)

Department für Lithosphärenforschung

Externe Organisation(en)

Univerzita Komenského v Bratislave, University of Arizona, Naturhistorisches Museum Wien (NHM), Istituto Nazionale di Fisica Nucleare (INFN), Roma, Hungarian Academy of Sciences

Journal

Meteoritics and Planetary Science

Band

50

Seiten

273-286

Anzahl der Seiten

14

ISSN

1086-9379

DOI

https://doi.org/10.1111/maps.12419

Publikationsdatum

02-2015

Peer-reviewed

Ja

ÖFOS 2012

105105 Geochemie, 105116 Mineralogie

ASJC Scopus Sachgebiete

Geophysics, Space and Planetary Science

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/cosmogenic-radionuclides-and-mineralogical-properties-of-the-chelyabinsk-ll5-meteorite-what-do-we-learn-about-the-meteoroid(2d6c119b-c136-408c-9cd1-b4c08f8f19bf).html