Cosmic-ray exposure ages of pallasites

Herzog, G. F.; Cook, D. L.; Cosarinsky, M.; Huber, L.; Leya, Ingo; Park, J. (2015). Cosmic-ray exposure ages of pallasites. Meteoritics & planetary science, 50(1), pp. 86-111. Meteoritical Society at the University of Arkansas, Dept. of Chemistry and Biochemistry 10.1111/maps.12404

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We analyzed cosmogenic nuclides in metal and/or silicate (primarily olivine) separated from the main-group pallasites Admire, Ahumada, Albin, Brahin, Brenham, Esquel, Finmarken, Glorieta Mountain, Huckitta, Imilac, Krasnojarsk, Marjalahti, Molong, Seymchan, South Bend, Springwater, and Thiel Mountains and from Eagle Station. The metal separates contained an olivine fraction which although small, <1 wt% in most cases, nonetheless contributes significantly to the budgets of some nuclides (e.g., up to 35% for Ne-21 and Al-26). A correction for olivine is therefore essential and was made using model calculations and/or empirical relations for the production rates of cosmogenic nuclides in iron meteoroids and/or measured elemental concentrations. Cosmic-ray exposure (CRE) ages for the metal phases of the main-group pallasites range from 7 to 180 Ma, but many of the ages cluster around a central peak near 100 Ma. These CRE ages suggest that the parent body of the main-group pallasites underwent a major break-up that produced most of the meteorites analyzed. The CRE age distribution for the pallasites overlaps only a small fraction of the distribution for the IIIAB iron meteorites. Most pallasites and IIIAB irons originated in different collisions, probably on different parent bodies; a few IIIABs and pallasites may have come out of the same collision but a firm conclusion requires further study. CRE ages calculated from noble gas and radionuclide data of the metal fraction are higher on average than the Ne-21 exposure ages obtained for the olivine samples. As the metal and olivine fractions were taken in most cases from different specimens, the depth-dependency of the production rate ratio Be-10/Ne-21 in metal, not accounted for in our calculations, may explain the difference.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Physics Institute

UniBE Contributor:

Leya, Ingo

Subjects:

500 Science > 520 Astronomy
500 Science > 530 Physics

ISSN:

1086-9379

Publisher:

Meteoritical Society at the University of Arkansas, Dept. of Chemistry and Biochemistry

Language:

English

Submitter:

Katharina Weyeneth-Moser

Date Deposited:

14 Jun 2016 14:57

Last Modified:

06 Jul 2016 15:54

Publisher DOI:

10.1111/maps.12404

Web of Science ID:

000347707000005

BORIS DOI:

10.7892/boris.81670

URI:

https://boris.unibe.ch/id/eprint/81670

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