TY - JOUR

T1 - Dating and Tracing the Origin of Enstatite Chondrite Chondrules with Cr Isotopes

AU - Zhu, Ke

AU - Moynier, Frederic

AU - Schiller, Martin

AU - Bizzarro, Martin

PY - 2020

Y1 - 2020

N2 - Chondrules are major components of chondrites and are believed to drive the accretion of planetary embryos. As such, constraining the timing and origin of chondrules is central for understanding the early evolution of the solar system and the formation of planets. Enstatite chondrites (ECs) have isotope compositions for multiple elements that match that of the Earth and, thus, are considered to be good analogs of the precursor material from which the Earth formed. Here, we report the first high-precision mass-independent Cr isotope data of nine chondrules in one of the least-altered EH chondrites, Sahara 97096. Seven primitive chondrules show typical Cr-54/Cr-52 ratios of bulk ECs, whereas two chondrules have ratios similar to carbonaceous chondrites. The presence of two chondrules with a carbonaceous chondrite signature suggests early inward transport of material to the EC accretion region. The Mn/Cr ratios of the EC-like chondrules (except one with high Fe content) correlate with their Cr-53/Cr-52 isotope ratios, which we interpret as a fossil isochron, with a slope corresponding to a Mn-53/Mn-55 initial ratio of (5.01 0.59) x 10(-6) (2 sigma). When anchored to the D'Orbigny angrite, this Mn-53/Mn-55 ratio returns an absolute age of 4565.7 0.7 Ma for EC chondrule formation (precursor age), 1.6 0.7 Ma after solar system formation. This protracted formation of EC chondrules may suggest that the mass transfer of outer solar system material started prior to the end of planetary embryo accretion, as chondrules could represent the main building blocks of terrestrial planets.

AB - Chondrules are major components of chondrites and are believed to drive the accretion of planetary embryos. As such, constraining the timing and origin of chondrules is central for understanding the early evolution of the solar system and the formation of planets. Enstatite chondrites (ECs) have isotope compositions for multiple elements that match that of the Earth and, thus, are considered to be good analogs of the precursor material from which the Earth formed. Here, we report the first high-precision mass-independent Cr isotope data of nine chondrules in one of the least-altered EH chondrites, Sahara 97096. Seven primitive chondrules show typical Cr-54/Cr-52 ratios of bulk ECs, whereas two chondrules have ratios similar to carbonaceous chondrites. The presence of two chondrules with a carbonaceous chondrite signature suggests early inward transport of material to the EC accretion region. The Mn/Cr ratios of the EC-like chondrules (except one with high Fe content) correlate with their Cr-53/Cr-52 isotope ratios, which we interpret as a fossil isochron, with a slope corresponding to a Mn-53/Mn-55 initial ratio of (5.01 0.59) x 10(-6) (2 sigma). When anchored to the D'Orbigny angrite, this Mn-53/Mn-55 ratio returns an absolute age of 4565.7 0.7 Ma for EC chondrule formation (precursor age), 1.6 0.7 Ma after solar system formation. This protracted formation of EC chondrules may suggest that the mass transfer of outer solar system material started prior to the end of planetary embryo accretion, as chondrules could represent the main building blocks of terrestrial planets.

KW - Astrochemistry

KW - Cosmochemistry

KW - Cosmochronology

KW - Solar system

KW - Isotopic abundances

KW - Meteoroids

KW - Chondrules

KW - Nucleosynthesis

KW - Chondrites

KW - EARLY SOLAR-SYSTEM

KW - AL-26-MG-26 SYSTEMATICS

KW - MN-53-CR-53 CHRONOMETRY

KW - INDIVIDUAL CHONDRULES

KW - OXYGEN-ISOTOPE

KW - CHRONOLOGY

KW - SULFIDES

KW - INSIGHTS

KW - EARTH

KW - AGES

U2 - 10.3847/2041-8213/ab8dca

DO - 10.3847/2041-8213/ab8dca

M3 - Journal article

VL - 894

JO - The Astrophysical Journal Letters

JF - The Astrophysical Journal Letters

SN - 2041-8205

IS - 2

M1 - 26

ER -