A time-resolved paleomagnetic record of Main Group pallasites: Evidence for a large-cored, thin-mantled parent body

1,2Claire I. O. Nichols,2James F.J. Bryson,3Rory D. Cottrell,4Roger R. Fu,1Richard J. Harrison,5,6Julia Herrero-Albillos,7Florian Kronast,3John A. Tarduno,4Benjamin P. Weiss
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2021JE006900]
1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Insitute of Technology, Cambridge, MA, 02139 USA
2Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN UK
3Department of Earth and Environmental Sciences, University of Rochester, NY, 14627 USA
4Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA
5Centro Universitario de la Defensa, Carretera de Huesca s/n, E-50090 Zaragoza, Spain
6Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC—Universidad de Zaragoza, Zaragoza, 50009 Spain
7Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
Copyright Elsevier

Several paleomagnetic studies have been conducted on five main group pallasites: Brenham, Marjalahti, Springwater, Imilac and Esquel. These pallasites have distinct cooling histories, meaning that their paleomagnetic records may have been acquired at different times during the thermal evolution of their parent body. Here we compile new and existing data to present the most complete time-resolved paleomagnetic record for a planetesimal, which includes a period of quiescence prior to core solidification as well as dynamo activity generated by compositional convection during core solidification. We present new paleomagnetic data for the Springwater pallasite, which constrains the timing of core solidification. Our results suggest that in order to generate the observed strong paleointensities ( ∼ 65 – 95 μT), the pallasites must have been relatively close to the dynamo source. Our thermal and dynamo models predict that the main group pallasites originate from a planetesimal with a large core (> 200 km) and a thin mantle (< 70 km).


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