VOLATILE EVOLUTION IN ARCHEAN RARE.ELEMENT GRANITIC PEGMATITES: EVIDENCE FROM THE HVDROGEN ISOTOPIC COMPOSITION
Bibliographic record
Abstract
The channel H2O in beryl constitutes a large reservoir of molecular water; concentrations attain 2.4wt.o/0. Stepwise heating experiments, carried ovt in vacuo, permitted the differential extraction of both the channel H2O and water from other minor sources (e.g., fluid inclusions) for quantification and hydrogen isotope analysis. Beryl is a ubiquitous primary mineral in the two groups of Late Archean granitic pegmatites that occur in the Dryden area, in Ontario, and the hydrogen isotope composition of its channel H2O has a range of ca. 25o/or. Igneous fractionation trends in the rare-element granitic pegmatites of the Mavis Lake group, the focus of this study, are described by: (l) systematic changes in the mineral assemblage of the pegmatites with increasing distance from the parent granire (beryl to spodumene- beryl- tantalite), (2) decreasing K,/Rb ratio in blocky K-feldspar that coexists with beryl (K/RbKrs = 59 to 16), (3) increasing concentrations of channel H2O in beryl (1.16 to 2.25 wt.t/o), and (4) increasing 6D values in beryl (-78 to-53%o). As there is no compelling field or petrographic evidence for vapor saturation during the bulk of pegmatite crystallization, these trends are interpreted to have resulted from crystallization at vapor-undersaturated conditions, with the composition of the channel H2O in the beryl approximating that of dissolved magmatic H2O. Hydrogen isotope fractionations between muscovite and the channel H2O in coexisting beryl from the Taylor Beryl No. 2 (A1,4r-1-1,o:-2lo/oi and Fairservice Property No. 1 (Ayr_g 190loo) pegmatites are analytically
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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 | 0.001 | 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".