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Recrystallized Taenite lamellae aggregates in Seneca Falls |
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| Meteorite, Seneca Falls, IIAB Iron. |
| Figure 1.. Scale bar 100 µm. |
| Meteorite, Seneca Falls, IIAB Iron. |
| Recrystallized taenite aggregates. |
| Recrystallized segments of
taenite lamellae consist of metallic aggregates that have experienced intense
shock reheating. The strings of amoeba-shaped particles observed in these
structures are a direct outcome of an impact and shock event. In the Seneca Falls meteorite, taenite lamellae are fragmented into segments ranging from 50 to 400 µm. This segmentation reflects a powerful shock reheating event that caused the taenite to fracture and recrystallize in situ. Under certain conditions of temperature and cooling rates, taenite within iron meteorites can recrystallize and form spheroidal, amoeba-like shapes. Such transformations typically occur during episodes of severe shock reheating. Recrystallization of taenite begins at temperatures between 500°C and 700°C. Within this range, the taenite reorganizes into smaller, more stable grains. For taenite to spheroidize into amoeba-like particles, temperatures must stabilize just below the eutectoid point (approximately 700°C) for a prolonged duration. This extended heating allows the taenite to disintegrate and reshape into spheroidal and amoeba-like forms. When taenite cools slowly from just below the eutectoid temperature, it undergoes a phase transition. The high-temperature, face-centered cubic taenite begins to decompose into a mix of lower-temperature phases, including kamacite (body-centered cubic iron-nickel) and other iron-nickel alloys. During this transformation, taenite can develop spheroidized particles resembling tiny amoebas. This occurs as the taenite phase reduces its surface energy, adopting rounded, spheroidal configurations. |
| Figure 2. Scale bar 100 µm. |
| Meteorite, Seneca Falls, IIAB Iron. |
| Recrystallized taenite aggregates. |
| Figure 3. Scale bar 100 µm. |
| Meteorite, Seneca Falls, IIAB Iron. |
| Recrystallized taenite aggregates. |
| Figure 4. Scale bar 100 µm. |
| Meteorite, Seneca Falls, IIAB Iron. |
| Recrystallized taenite aggregates. |
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