Unique achondritic impact debris in the CH3 chondrite Acfer 182
Kainen L. Utt, Ryan C. Ogliore, Michael J. Krawczynski, Paul K. Carpenter, Alian Wang
Geochemistry, In Press, Journal Pre-proof, Available online 22 October 2024
“The metal-rich CH carbonaceous chondrites contain abundant xenolithic clasts originating from different regions of the Solar System. In the CH3 chondrite Acfer 182, we identified two phosphide spherules (one 95-μm in diameter and the other 50 μm x 60 μm) of schreibersite ((Fe,Ni)3P) and barringerite ((Fe,Ni)2P) with kamacite eutectic structures. These objects are likely to have formed during an impact between planetesimals during the debris-disk phase of the protoplanetary disk before being incorporated into the CH chondrite parent body. In the same sample we identified a 130 μm x 60 μm heideite grain (iron‑titanium sulfide: (Fe,Cr)1.15(Ti,Fe)2S4) with exsolution lamellae of calcium-rich titanium oxide. Thin veins of shock-induced kamacite cross-cut the oxide lamellae, suggesting that it was ejected into the protoplanetary debris disk during an impact event before eventually being accreted by the CH chondrite parent body. This assemblage is distinct from heideite grains found in enstatite chondrites, aubrites, and the Kaidun meteorite. We propose that this object originated from a highly-reduced planetesimal in the inner Solar System that may have been similar to proto-Mercury.”
