Chondrite diversity revealed by chromium, calcium and magnesium isotopes

Ke Zhu*, Martin Schiller, Frédéric Moynier, Mirek Groen, Conel M.O.D. Alexander, Jemma Davidson, Devin L. Schrader, Addi Bischoff, Martin Bizzarro

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

2 Citations (Scopus)


Chondrites are undifferentiated meteorites that can provide information on the compositions of materials in the early solar System, including the building blocks of the terrestrial planets. While most chondrites belong to well-defined groups based on their mineralogy and chemical composition, a minor fraction have unusual characteristics and are classified as ungrouped chondrites. These ungrouped chondrites reflect the diversity of chondritic materials in the early solar system; however, they are not as well studied as grouped meteorites and their origins are poorly understood. In this study, we present high-precision mass-independent Cr, Ca and Mg isotope data for 17 ungrouped chondrites. The ε54Cr and ε48Ca (ε expresses parts per ten thousand mass-independent isotope deviation) data for ungrouped chondrites also provide important constraints for assessing their relationships to the known chondrite groups, and the radiogenic Mg isotope ratios (μ26Mg*) can be used to track the early solar system history. We also present the first high-precision data for a Kakangari (KC) chondrite, an enstatite chondrite, and for four enstatite-rich meteorites. The ε54Cr and ε48Ca values for the KC are −0.44 ± 0.04 and −1.30 ± 0.25, respectively, and ε48Ca value for SAH 97096 (EH3) is −0.19 ± 0.22 that overlaps with that of those of Earth-Moon system and ordinary chondrites. All the carbonaceous chondrite-like (CC) ungrouped chondrites show positive ε54Cr and ε48Ca values, and all the non-carbonaceous chondrite-like (NC) ungrouped chondrites and KCs (also belong to the NC trend) show zero or negative ε54Cr and ε48Ca values. This observation confirms the CC-NC dichotomy for primitive solar system materials. LEW 87232 (KC) also shows the highest 55Mn/52Cr ratio and ε53Cr value amongst all the chondrites. There is a positive trend between 55Mn/52Cr ratios and ε53Cr values among all the chondrites that mostly reflects a mixing between multiple chondritic components. Previously it has been reported that there is a bulk 26Al-26Mg correlation line amongst chondrites. This correlation has been interpreted as being due to mixing of CAIs (high 27Al/24Mg ratios and μ26Mg* values) and other silicate material (e.g., chondrules and matrix). By providing additional 26Al-26Mg chondrite data, we show that there is no 26Al-26Mg correlation line for the chondrites, ruling out the two-endmember (i.e., CAIs and other silicates) mixing model.

Original languageEnglish
Pages (from-to)156-168
Number of pages13
JournalGeochimica et Cosmochimica Acta
Early online date29 Dec 2022
Publication statusPublished - 1 Feb 2023

Bibliographical note

Funding Information:
K. Z. thanks Alexander von Humboldt postdoc fellowship, China Scholarship Council (CSC) PhD fellowship (#201706340161), and a UK STFC grant (#ST/V000888/1). F. M. acknowledges funding from the European Research Council under the H2020 framework program/ERC Starting Grant Agreement (#637503–PRISTINE) and financial support of the UnivEarthS Labex program at Sorbonne Paris Cité (#ANR–10–LABX–0023 and #ANR–11–IDEX-0005-02), and the ANR through a chaire d’excellence Sorbonne Paris Cité. M. B. acknowledges funding the Carlsberg Foundation (CF18-1105), the Danish National Research Foundation (DNRF97) and the European Research Council (ERC Advanced Grant Agreement, #833275–DEEPTIME). M. S. acknowledges funding from the Villum Fonden (#00025333). Pierre Burckel is acknowledged for ICP-MS analysis, and Matt Jackson is acknowledged for providing the two terrestrial peridotites. Parts of this work were supported by IPGP multidisciplinary program PARI, and by Paris–IdF region SESAME (#12015908). US Antarctic meteorite samples are recovered by the Antarctic search for Meteorites (ANSMET) program which has been funded by NSF and NASA, and characterized and curated in the Department of Mineral Sciences of the Smithsonian Institution and Astromaterials Curation Office at NASA Johnson Space Center. Yun Jiang is appreciated for providing Ningqiang meteorite. Comments from Stefan Weyer (AE) and three anonymous reviewers improved this manuscript.

Publisher Copyright:
© 2022 The Author(s)


  • Al-Mg Isochron
  • Mn-Cr Isochron
  • CC-NC dichotomy
  • Chondrites
  • Cr, Ca and Mg isotopes
  • Mass-independent isotope fractionation
  • Meteorite classification


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