154 Asteroid Observations, Return Missions, and Meteoritics: Interweaving Perspectives and Data (Posters)

The new age of sample return missions affords opportunities to intercalibrate observational and laboratory results. This session invites studies using observational tools, return mission data and materials, and meteorites to advance our knowledge of asteroids.

Monday, 20 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Incomplete Tetrataenite Disorder in Moderately Shocked Ordinary Chondrites: Insights from Rock Magnetism and Scanning Transmission Electron Microscopy

Paper number: 154-3
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

Tetrataenite (γ̋-ordered face-centered cubic, equiatomic FeNi) forms in equilibrated (type 4–6) ordinary chondrites as a result of thermal metamorphism on their parent bodies at temperatures of 700–950 °C, followed by slow cooling [1]. Due to its exceptional magnetic hardness, tetrataenite is readily detectable using magnetic methods. However, while non-shocked or weakly shocked (S1–S3) ordinary chondrites typically contain abundant tetrataenite, conventional magnetometry approaches often indicate an absence of the mineral in higher shock grade (S4–S6) meteorites (e.g., [2]). It is generally assumed that strong impact-related pressure and temperature surges lead to irreversible disordering of tetrataenite into magnetically soft taenite.

A recent study of the Daule chondrite (L5, S4, W0) [3] suggested differential post-shock survival of tetrataenite at the millimeter scale, indicating heterogeneity in impact-related thermal and pressure conditions. The study also proposed that remanent magnetization-based methods are more sensitive to detecting minor amounts of tetrataenite than induced magnetization approaches. These findings support the hypothesis that S4-grade metamorphism may not uniformly exceed the threshold for complete tetrataenite disordering [4].

To further test this hypothesis, we investigated twelve ordinary chondrites (shock grades S3–S6) using a comprehensive suite of rock magnetic techniques. These included thermomagnetic analysis at both high and cryogenic temperatures, magnetic hysteresis and backfield demagnetization, first-order reversal curve (FORC) measurements, and thermal and alternating field demagnetization of natural remanent magnetization. Samples exhibiting high-coercivity signals were further analyzed for tetrataenite using scanning transmission electron microscopy (STEM). For these analyses, the samples were crushed, magnetically separated from the matrix, and dispersed in fluid. Using high-angle annular dark-field (HAADF) imaging, we identified and indexed individual grains and imaged clusters of magnetic alloys.

[1] Yang et al. (1997), Geochim. Cosmochim. Acta 61, 2943–2956.

[2] Gattacceca et al. (2014), Meteorit. Planet. Sci. 49, 652–676.

[3] Bristol et al. (2023), Icarus, 404, 115684.

[4] Scorzelli et al. (1987), J. Phys. F: Met. Phys. 17, 1993–1997.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-414499

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.