Primordial formation of major silicates in a protoplanetary disc with homogeneous 26Al/27Al

Gregory, Timothy; Luu, Tu-Han; Coath, Christopher D.; Russell, Sara S.; Elliott, Tim. 2020 Primordial formation of major silicates in a protoplanetary disc with homogeneous 26Al/27Al. Science Advances, 6 (11), eaay9626.

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Understanding the spatial variability of initial 26Al/27Al in the solar system, i.e., (26Al/27Al)0, is of prime importance to meteorite chronology, planetary heat production, and protoplanetary disc mixing dynamics. The (26Al/27Al)0 of calcium-aluminum–rich inclusions (CAIs) in primitive meteorites (~5 × 10−5) is frequently assumed to reflect the (26Al/27Al)0 of the entire protoplanetary disc, and predicts its initial 26Mg/24Mg to be ~35 parts per million (ppm) less radiogenic than modern Earth (i.e., Δ′26Mg0 = −35 ppm). Others argue for spatially heterogeneous (26Al/27Al)0, where the source reservoirs of most primitive meteorite components have lower (26Al/27Al)0 at ~2.7 × 10−5 and Δ′26Mg0 of −16 ppm. We measured the magnesium isotope compositions of primitive meteoritic olivine, which originated outside of the CAI-forming reservoir(s), and report five grains whose Δ′26Mg0 are within uncertainty of −35 ppm. Our data thus affirm a model of a largely homogeneous protoplanetary disc with (26Al/27Al)0 of ~5 × 10−5, supporting the accuracy of the 26Al→26Mg chronometer.

Item Type: Publication - Article
Digital Object Identifier (DOI):
ISSN: 2375-2548
Date made live: 02 Jul 2020 14:40 +0 (UTC)

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