Dominik C. Hezel

Modal abundances of CAIs: Implications for bulk chondrite element abundances and fractionations

Modal abundances of Ca,Al-rich inclusions (CAIs) are poorly known and reported data scatter across large ranges. CAIs are Poisson distributed, and if only small areas (<1000 mm2) are studied, the data are probably not representative of the true CAI modal abundances, explaining their reported large scatter in a single chondrite group. We combine reported CAI modal abundances and our own set, and present a complete list of CAI modal abundances in carbonaceous chondrites. This includes (in area%): CV: 2.98, CM: 1.21, Acfer 094: 1.12, CO: 0.99, CK/CV (Ningqiang and Dar al Gani [DaG] 055): 0.77, CK: 0.2, CR: 0.12 and CB: 0.1. CAIs are Poisson distributed and if only small areas are studied, the data are probably not representative of the true CAI modal abundances, Carbonaceous chondrites have excess bulk Al concentrations when compared to the CI-chondritic value. We find a correlation between this excess and CAI modal abundances and conclude that the excess Al was delivered by CAIs. The excess Al is only a minor fraction (usually ~10 rel%, but 25 rel% in case of CVs) of the bulk chondrite Al and cannot have contributed much 26Al to heat the chondrite parent body. Ordinary, enstatite, R and K chondrites have an Al deficit relative to CI chondrites and only very low CAI modal abundances, if any are present at all. Carbonaceous chondrites also had an initial Al deficit if the contribution of Al delivered by CAIs is subtracted. Therefore all chondrites probably lost a refractory rich high-T component. Only minor amounts of CAIs are present in the matrix or have been present in the chondrule precursor aggregates. Most CAI size distributions contain more than one size population, indicating that CAIs from within a single meteorite group had different origins.

Pyroxenes : a new class of multiferroics

Pyroxenes with the general formula

Improved segmentation of meteorite micro-CT images using local histograms

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PhaseQuant: A tool for quantifying tomographic data sets of geological specimens

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Tracing the oxygen isotope composition of the upper Earth's atmosphere using cosmic spherules

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Comment on "Ancient Asteroids Enriched in Refractory Inclusions"

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Sr stable isotope composition of Earth, the Moon, Mars, Vesta and meteorites

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The chemical relationship between chondrules and matrix and the chondrule matrix complementarity

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Constraints for chondrule formation from Ca–Al distribution in carbonaceous chondrites

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The conditions of chondrule formation, Part I: Closed system

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