Replication Data for: Formation of diamond and lonsdaleite in ureilites by impact shock processing of graphite

Carbon phase assemblages (CPAs) in five ureilitic samples from asteroid 2008 TC3 were analyzed using transmission electron microscopy, Raman spectroscopy, synchrotron X-ray diffraction, and cathodoluminescence. 2. Shock Degrees of Samples: Samples MS-MU 006, MS-187, and MS-170 had low to moderate shock degrees (U-S2 and U-S3), while samples MS-MU 027 (U-S4) and MS-MU 045 (U-S5) experienced higher shock levels. 3. Presence of Diamond Grains: No diamond grains were found in samples MS-MU 006 and MS-187.

Sample MS-170 contained diamond grains up to 12 μm, formed under relatively low shock pressures (5–15 GPa) with a catalytic process involving a Fe, Ni, Cr, S, P-rich melt. 4. CPAs in Highly Shocked Samples: MS-MU 027 and MS-MU 045, the highly shocked ureilites, displayed three types of CPAs: nanopolycrystalline diamond and defect-rich diamond/lonsdaleite, disordered and distorted graphite, and polycrystalline diamond with Fe-rich mineral inclusions. 5.

Formation Mechanisms: CPAs with only diamond and planar defect-rich diamond (e.g., MS-MU 027) likely formed through martensitic transformation of graphite at >15 GPa and >2000 K. Assemblages of diamond, defect-rich diamond, and disordered graphite (e.g., MS-MU 045) underwent martensitic transformation followed by back-transformation to disordered graphite. No conclusive evidence supports diamond formation under high static pressure.