Redox-sensitive partitioning of vanadium and other heterovalent elements between apatite and biotite in high silica magmas
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Bibliographic record
Abstract
Apatite and biotite, ubiquitous minerals in a multitude of rock types, host a variety of trace elements, including those whose valence state, and hence ionic radius and charge, can vary over the oxygen fugacity (fO2) of natural magmatic systems. In this study, we determine trace element (X) partition coefficients in five suites of natural, mostly silicic, metaluminous to peraluminous rocks that formed under reduced to oxidized conditions (FMQ-3.6 to +6.2; FMQ = fayalite-magnetite-quartz buffer). The analyzed suites include Fish Canyon tuff (FCT, USA), Mascota minette (MM, Mexico), Picotani intrusive suite (MAC, Peru), Tuk-Tuk tuff (TT, Indonesia), and Umiakovik pluton (UP, Canada). In three of the suites (MAC, TT, FCT), representing a narrower fO2 range (FMQ-3.6 to 2.9), trace element apatite/glass and biotite/glass partition coefficients (DXap/gl =CXapatite/CXglass and DXbt/gl = CXbiotite/CXglass, respectively) were also determined. Elements considered include alkalis, alkaline earths, rare earth elements, transition metals, metalloids, and high field strength elements, of which V, As, Eu, Mo, Sn, and W are expected to be present in species of more than one valence state (heterovalent) over the fO2 range considered. Results reveal changes in partitioning behavior of the heterovalent elements over the sample fO2 range. With increasing fO2 from FMQ-3.6 to FMQ+2.9, values of DVbt/gl decrease from ~580 to ~50 whereas DVap/gl increases from ~0.5 to ~5. Arsenic becomes more compatible in apatite with DAsap/gl increasing from ~ 0.04 to ~1.6. Values of Dap/gl for Eu increase from ~20 to ~90. Molybdenum Dbt/gl decreases from ~2 to ~0.1. Tin becomes more compatible with both minerals as fO2 increases, with DSnbt/gl increasing from ~0.1 to ~1.0 and DSnap/gl from ~0.05 to ~0.3. Although the uncertainty on DWap/gl is too large to derive a meaningful fO2 relation, values for DWbt/gl decrease from ~0.13 to ~0.02 with increasing fO2. As a result of DVap/gl and DVbt/gl exhibiting opposite relations with fO2, values of apatite/biotite partitioning (DVap/bt) systematically increase from ~0.001 to ~0.5 with an increase in fO2.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.000 | 0.001 |
| 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 it