Sustained recycling of anorthite-rich inclusions by outer-disk chondrule heating events
Mingming Zhang, Kohei Fukuda, Michael J. Tappa, William O. Nachlas, Bil Schneider, Makoto Kimura, Kouki Kitajima, Ann M. Bauer, Noriko T. Kita
Geochimica et Cosmochimica Acta
In Press, Journal Pre-proof, Available online 2 January 2026
“Chondrules, ferromagnesium spherules prevalent in undifferentiated extraterrestrial materials, are the main high-temperature products of the protoplanetary disk. Relict minerals within them directly record precursor compositions and thermal histories, offering critical constraints on the long-debated chondrule heating mechanism. We identified pervasive relict refractory anorthites in Al-rich chondrules (bulk Al2O3 ≥10 wt%, ARCs) from pristine carbonaceous chondrites. These anorthites form rims around relict spinel aggregates or intergrow with high-Ca pyroxene/olivine relics, indicating preferential recycling of anorthite-rich inclusions during outer-disk chondrule heating events over more abundant melilite-rich ones. The wide occurrence of relict anorthite, which can be readily melted or dissolved in chondrule melts, suggests these ARCs were most likely formed by one-time crystallization. Thus, their Al-Mg ages of ∼2.0–2.5 Ma after CAIs imply refractory materials were continuously involved over nearly the entire period of chondrule formation. Additionally, we infer that a portion of co-formed iron-poor ferromagnesium chondrules must have similarly escaped completely remelting by subsequent intense heating events in the same reservoirs. These findings suggest that the intense heating events that lead to carbonaceous chondrule formation are localized and infrequent, aligning with mechanisms like bow shocks, lightning discharges, and impact jetting but not the large-scale nebular shocks.”
