Complex Nanostructures in Shocked, Annealed, and Metamorphosed Baddeleyite Defined by Atom Probe Tomography
Bibliographic record
Abstract
Chemical and isotopic signatures recorded by the accessory phase baddeleyite (ZrO2) yield important insights into the formation and evolution of mafic planetary crusts. However, little work has been conducted regarding the effects of structures on the mobilization and diffusion of substitutional and interstitial ions. Coupled nanometer-scale analyses of chemistry and structure in mineral phases are possible using the emerging technique of atom probe tomography (APT). Here we use this technique to describe a range of complex chemical nanostructures within shocked, annealed, and metamorphosed baddeleyite grains sampled in crater floor rocks ~550 m away from the contact with the Sudbury impact melt sheet. This has revealed a wide range of nanostructural phenomena, including domains of clustered incompatible cations (Fe), separated by subgrain boundaries or planar features exhibiting wave-like features decorated with trace amounts of Al, Si, and Fe likely generated by shock metamorphism. In some cases, these nanostructures have facilitated much later, and highly localized, postimpact Pb loss and Si gain ascribed to regional greenschist metamorphism. Characterizing nanoscale heterogeneities within complex, shocked baddeleyite grains using APT for resolution of different deformation pathways and a more confident interpretation of the geologic significance of micron-scale trace element and isotopic analyses.
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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".