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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. |
| Segments of recrystallized
taenite lamella are aggregates of metal that have undergone severe shock
reheating. Strings of amoeba-like particles are the reheating result of a
cosmic shock event. The taenite lamellae are subdivided into segments in the Seneca Falls meteorite, each 50 to 400 µm across. This subdivision indicates an event of severe shock reheating, which caused the taenite to break into smaller segments and recrystallize in place. Under specific conditions of temperature and cooling rates, taenite in iron meteorites can recrystallize and spheroidize into amoeba-like structures. This process typically occurs during severe shock reheating events. Taenite begins to recrystallize at temperatures around 500° C to 700° C. This range allows the taenite to transform into smaller, more stable grains. For taenite to spheroidize into amoeba-like particles, the temperature needs to be slightly below the eutectoid temperature (around 700° C) and maintained for an extended period. This prolonged heating allows the taenite to break down and form amoeba-like and spheroidal structures. When taenite is cooled slowly to just below this eutectoid temperature, it begins to transform. The high-temperature taenite phase (which is face-centered cubic) starts to break down into a mixture of lower-temperature phases, such as kamacite (body-centered cubic iron-nickel) and other iron-nickel alloys. The taenite can form spheroidized particles that resemble tiny amoebas during this transformation. This happens because the taenite phase tries to minimize its surface energy, forming rounded, spheroidal shapes. |
| 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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