¹Ling-Zhi Hu, ¹Maxence Regnault, ¹Philipp Gleißner, ¹Ninja Braukmüller, ²Ashley J. King, ¹Anne Lindner, ¹Harry Becker
Earth and Planetary Science Letters, 695, 120270 Open Access Link to Article [DOI: 10.1016/j.epsl.2026.120270]
¹Institut für Geologische Wissenschaften, Freie Universität Berlin, Malteserstrasse 74-100, Berlin, D-12249, Germany
²Planetary Materials Group, Natural History Museum, Cromwell Road, London, SW7 5BD, UK
Copyright Elsevier

Carbonaceous chondrites (CCs) exhibit profound non-systematic heterogeneity in their elemental and isotopic compositions, both within individual meteorite splits and among bulk samples of the same group, providing opportunities for a better understanding of early solar system processes. This variability also poses significant challenges for constraining bulk compositions of the parent bodies. We report new mass-independent Ti and Cr isotope data, integrated with major and trace element abundances for a suite of CC bulk rocks, to better understand the origin of this multiscale heterogeneity. Some bulk CCs (e.g., Yamato chondrites and Allende) exhibit elemental or isotopic compositions consistent with the literature, while others display significant differences.

Simple binary or ternary mixtures, using ε⁵⁰Ti, ε⁵⁴Cr and chemical data from the present study and literature as constraints, cannot reproduce the full range of isotopic and elemental data. The data are best explained by a multi-component mixing model with a minimum of four endmembers, involving CI-like matrix, heterogeneous non-carbonaceous (NC) dust, and two distinct refractory inclusion populations. The latter are similar to the average composition of calcium-aluminium-rich inclusions (CAIs) and amoeboid olivine aggregates (AOAs) and a CAI-like component found in some chondrules. Crucially, the model constraints reveal that NC dust, which migrated into the CC region, contained chemically fractionated material, characterized by a significant depletion in siderophile elements. This result suggests that some NC dust in CC may represent silicate-rich debris derived from the collision of early differentiated planetesimals in the inner solar system. Thus, carbonaceous chondrites record a multi-stage history of early transport of variably ⁵⁰Ti- and ⁵⁴Cr-enriched CAIs and subsequent migration of chondritic and differentiated planetary debris into CI chondrite-like icy dust of the outer disk.