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Recrystallized Hexahedrite |
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| Meteorite - Carver, IIAB Iron. |
| Figure 1. Scale bar 100 µm. |
| Meteorite: Carver, IIAB, Iron |
| Recrystallized kamacite. |
| Meteorite - Carver, IIAB Iron
Figure 1. Scale bar 100 µm. Meteorite: Carver, IIAB, Iron Recrystallized kamacite. Iron meteorites recrystallize primarily due to shock events and reheating processes. High-energy impacts in space or collisions with other celestial bodies generate extreme heat and pressure, triggering recrystallization. This process disrupts the meteorite’s original crystal structure, breaking it down and forming smaller grains of key minerals like kamacite and taenite. Reheating plays a vital role in recrystallization and can occur due to proximity to a heat source, such as a molten core, or from subsequent impacts. During reheating, the metal may partially melt and then cool slowly, allowing new crystal structures to develop. For instance, forming uniform 20 µm taenite grains with varied orientations could take roughly 800 years at 600°C or just 1 hour at 1,300°C, according to Goldstein et al. (2011, Meteoritics & Planetary Science). Recrystallization can also alter the meteorite’s chemical composition. As a result, recrystallized iron meteorites often exhibit a finer, more granular texture compared to their original form. |
| References Key Primary Sources • Goldstein, J. I., Yang, J., & Scott, E. R. D. (2011). Thermal and impact histories of reheated group IVA, IVB, and ungrouped iron meteorites and their parent asteroids. Meteoritics & Planetary Science (or related works by the Goldstein group). The Goldstein research group has extensively documented recrystallization, annealing, and reheating effects in irons through metallography and cooling-rate modeling. • Buchwald, V. F. (1975). Handbook of Iron Meteorites. University of California Press (3 volumes). The classic reference. It describes recrystallized textures in many hexahedrites and IIAB irons (including shock-induced recrystallization of kamacite, secondary structures, and the effects of impact reheating). Look under individual meteorite entries and the general chapters on secondary structures and shock features. Hexahedrites (nearly pure kamacite) commonly show Neumann lines and, when shocked/reheated, recrystallized equiaxed grains. Additional Supporting Literature • Yang, J., Goldstein, J. I., et al. Various papers in Meteoritics & Planetary Science and Geochimica et Cosmochimica Acta (2000s–2010s). These discuss recrystallization, martensite decomposition, cloudy zone formation, and impact/reheating histories in iron meteorites, including timescales for grain growth and annealing. • Rubin, A. E. Papers on shock effects in iron meteorites (e.g., Meteoritics & Planetary Science, 2010s). Documents recrystallized kamacite, post-shock annealing, and multi-stage impact histories (relevant to IIAB and other groups). • Wasson, J. T. & colleagues. Chemical classification and metallographic studies of IIAB irons (hexahedrites and coarsest octahedrites). IIAB irons frequently exhibit recrystallization related to parent-body collisions. |
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