Ion imaging of ancient zircon
Bibliographic record
Abstract
The Idiwhaa gneiss, part of the Acasta Gneiss Complex, Canada, is a key source of information concerning formation of continental crust on the early Earth. However, zircon crystals from this oldest dated felsic crust were affected by multiple stages of alteration and metamorphism, leading to difficulties in disentangling primary from secondary processes. These grains provide an opportunity to understand the alteration processes that affect ancient zircon crystals. Ion imaging reveals pervasive recrystallisation fronts extending inwards from the margins of grains. Ahead of these recrystallisation fronts, grain cores contain isolated pockets of amorphous, but concordant, 3.99 Ga zircon that evidently escaped post-magmatic modification of U and Pb. The transport of these elements, involving the decoupling of parent and daughter isotopes, is highly heterogeneous over space and time within metamict zircon, yet localised domains still retain primary age information. Our data indicate that metamictisation of zircon alone does not lead to radiogenic Pb loss, which requires interaction with fluid.
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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 | 0.001 |
| 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) | 0.002 | 0.001 |
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".