Vanadium-bearing tourmaline in metacherts from Chvojnica, Slovak Republic: crystal chemistry and multistage evolution
Bibliographic record
Abstract
Vanadium-bearing tourmaline was found in Paleozoic metacherts near Chvojnica in the Stražovske vrchy Mountains, Slovakia. The geochemistry of metacherts suggests that the protolith was deposited under anoxic conditions. Tourmaline from Chvojnica displays strong chemical zoning, with high Mg and a very low Fe content. The core has the composition of magnesio-foitite with a low V content, and is mainly controlled by alkali-deficient substitution [ X □(Al,V)(NaMg) −1 ]. The other zones have a dravitic composition considering ordering of all Mg to the Y sites, but they may reach the composition of olenite if one proposes strong Al–Mg disorder (not proven by structural refinement). The intermediate zone is mostly enriched in V (up to 3.3 wt.% V 2 O 3 , 0.42 apfu V), and V is considered to be incorporated into the structure by VAl −1 substitution. Two rim zones were observed. Rim 1 is depleted in V but is enriched in Al. Rim 2 is similar in composition to the intermediate zone, with increased V. The increased content of trivalent cations, including Al, V and Cr in comparison to divalent Mg and Fe, suggests a deprotonation of (OH) − by the proton-deficient substitution Y (Al,V)O Y Mg −1 (OH) −1 . The increase of Ca, Ti and Mg content from core to rim may be the result of several substitutions, including TiMg(Al,V) −2 , CaMgO X □ −1 (Al,V) −1 (OH) −1 . The increase of Ca, Ti and Mg content from core to rim may be the result of several substitutions, including TiMg(Al,V) −2 , CaMgO X □ −1 (Al,V) −1 (OH) −1 . The V-bearing tourmaline from Chvojnica is the result of multistage Pre-Alpine regional metamorphism. The core of the grains is a product of the lower-grade M1 metamorphic event, whereas the intermediate zone corresponds to the second metamorphic event, M2. Medium-grade metamorphism (580
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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 | 0.001 | 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".