Thermal history of an amoeboid olivine aggregate in the early solar nebula

Abstract Carbonaceous chondrites commonly contain amoeboid olivine aggregates (AOAs). Here, we investigated an AOA in the CR chondrite Y‐793261. This AOA contains an unstable assemblage of forsterite and quartz. We found a rare occurrence of enstatite and quantitatively discuss its formation process. This enstatite occurs specifically between forsterite and quartz, indicating a solid‐state reaction between them. By applying the experimental results of Imae et al. (Proc. Japan Aca. 75: 229–234), we determined that this AOA formed under high‐temperature conditions (≳1169 K) over a period of approximately 1–5 years. The reservoir where the AOA formed was enriched in 16 O. Subsequently, it cooled rapidly and was transported to the reservoir where the parent body accreted, incorporating chondrules and matrix. The thermal history and physicochemical conditions of this AOA are applicable to other AOAs.