Early differentiation of magmatic iron meteorite parent bodies from Mn-Cr chronometry

TL;DR

This study uses Mn-Cr isotopic dating to determine that magmatic iron meteorite parent bodies formed their cores within 1.5 million years after CAIs, indicating early planetary differentiation in the solar system.

Contribution

It provides new Mn-Cr model ages for magmatic iron meteorites, refining the timing of core formation and constraining the initial E53Cr of the solar system.

Findings

Core formation occurred within 1.5 Ma after CAIs.

Supports early accretion and differentiation of parent bodies.

Refines initial E53Cr value of the solar system.

Abstract

Magmatic iron meteorite groups such as IIAB, IIIAB and IVA, represent the largest sampling of extraterrestrial core material from the earliest accreted distinct planetary bodies in the solar system. Chromium isotope compositions of chromite/daubreelite from seven samples, translated into 53Cr/52Cr model ages, provide robust time information on planetary core formation. These ages range within 1.5 Ma after formation of calcium-aluminium-rich inclusions (CAIs) and define the time of metal core formation in the respective parent bodies, assuming metal-silicate separation was an instantaneous event that induced strong chemical fractionation of Mn from the more siderophile Cr. The early core formation ages support accretion and differentiation of the magmatic iron meteorite parent bodies to have occurred prior to the chondrule formation interval. The calibration of Mn-Cr ages with established Hf-W ages of samples from the same magmatic iron meteorite groups constrains the initial E53Cr of the solar system to -0.30, and thus lower than previously estimated.