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

Claire I. O. Nichols, James F.J. Bryson, Rory D. Cottrell, Roger R. Fu, Richard J. Harrison, Julia Herrero-Albillos, Florian Kronast, John A. Tarduno, Benjamin P. Weiss

JGR Planets
First Published: 18 June 2021


“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).”