Ordinary chondrite shock stage quantification using in situ 2‐D X‐ray diffraction of olivine
Bibliographic record
Abstract
Abstract Ordinary chondrites record shock metamorphism resulting from hypervelocity collisions on small bodies, and underpin the petrographic assessment of shock stage, a scale of progressive stages of shock metamorphism from S1 (unshocked) to S7 (shock melted). In this work, olivine grains in 11 L and LL chondrites (S1–S5) were investigated in thin section and hand sample using in situ two‐dimensional X‐ray diffraction (2‐D XRD). Olivine grains were measured under a 300 µm X‐ray beam for multiple lattice reflections, by measuring diffracted streak length along the chi (χ) dimension (Debye ring dimension), to examine their strain‐related mosaicity. Olivine strain‐related mosaicity was observed to increase with greater shock deformation, with more complex multi‐peak streaks apparent at higher shock levels. The full width at half maximum (FWHMχ) of the simple peak shapes along χ was measured to quantify petrographic shock stage for comparison with that described optically. The average FWHMχ values for simple peaks in olivine show an increase with increasing shock stage: S1 (0.44°± 0.06°), S2 (0.58°± 0.11°), S3 (0.67°± 0.15°), S4 (0.76°± 0.13°), and S5 (0.86°± 0.12°). This method complements optical petrographic methods and offers a ±1 shock stage accuracy in determining shock stage. In particular, 2‐D XRD analysis of strain‐related mosaicity allows quantitative analysis of shock stage in shock‐darkened samples that are difficult to work with petrographically, and for hand samples without need for thin section preparation.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".