Aluminum‐Magnesium and Oxygen Isotope Study of Relict Ca‐Al‐rich Inclusions in Chondrules
Bibliographic record
Abstract
Relict Ca-Al-rich inclusions (CAIs) in chondrules crystallized before their host chondrules and were subsequently partly melted together with chondrule precursors during chondrule formation. Like most CAIs, relict CAIs are 16 O enriched (Δ 17 O < -20‰) compared to their host chondrules (Δ 17 O > -9‰). Hibonite in a relict CAI from the ungrouped carbonaceous chondrite Adelaide has a large excess of radiogenic 26 Mg ( 26 Mg*) from the decay of 26 Al, corresponding to an initial 26 Al/ 27 Al ratio [( 26 Al/ 27 Al) I ] of (3.7 ± 0.5) × 10 -5 ; in contrast, melilite in this CAI and plagioclase in the host chondrule show no evidence for 26 Mg* [( 26 Al/ 27 Al) I of <5 × 10 -6 ]. Grossite in a relict CAI from the CH carbonaceous chondrite PAT 91546 has little 26 Mg*, corresponding to a ( 26 Al/ 27 Al) I of (1.7 ± 1.3) × 10 -6 . Three other relict CAIs and their host chondrules from the ungrouped carbonaceous chondrite Acfer 094, CH chondrite Acfer 182, and H3.4 ordinary chondrite Sharps do not have detectable 26 Mg* [( 26 Al/ 27 Al) I < 1 × 10 -5 , <(4-6) × 10 -6 , and <1.3 × 10 -5 , respectively]. Isotopic data combined with mineralogical observations suggest that relict CAIs formed in an 16 O-rich gaseous reservoir before their host chondrules, which originated in an 16 O-poor gas. The Adelaide CAI was incorporated into its host chondrule after 26 Al had mostly decayed, at least 2 Myr after the CAI formed, and this event reset 26 Al- 26 Mg systematics.
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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) | 0.000 | 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".