Chemical and boron isotopic compositions of tourmaline from the Lavicky leucogranite, Czech Republic
Bibliographic record
Abstract
Abundant tourmaline occurs in the Lavicky leucogranite, Czech Republic as spherical to ovoid quartztourmaline orbicules, typically 5 to 7 cm in diameter.The tourmalines also occur as fine-grained quartztourmaline veins (<1 cm thick) that cut the orbicule-rich granite.Electron microprobe analyses reveal that tourmaline from the quartz-tourmaline orbicules is Fe-rich schorl with a range of Fe/(Fe+Mg) ratio 0.62 to 0.77 and Na/(Na+Ca) ratio 0.82 to 0.95.In contrast, tourmaline from quartz-tourmaline veins is Mg-rich dravite with a range of Fe/(Fe+Mg) ratio 0.23 to 0.45 and Na/(Na+Ca) ratio 0.67 to 0.90.Very low δ 11 B values of -37.3 to -32.1‰ are found in the tourmalines from the orbicules, whereas tourmalines from the veins display relatively higher δ 11 B values of -28.2 to -21.3‰.The overall large δ 11 B variation is suggested to reflect mixing of different boron sources and boron isotope fractionation during magmatic degassing and magmatic-hydrothermal evolution at late solidus to early subsolidus stages of granite crystallization.Only non-marine evaporites show very negative δ 11 B values (<-20‰) in all natural boron reservoirs, hence, the very low δ 11 B values of the quartz-tourmaline orbicules likely indicate a major contribution of boron from non-marine evaporites that probably exist in the magma source regions or assimilated into the magma during its ascent.Quartz-tourmaline orbicules may have formed during a transition from magmatic to hydrothermal processes, whereas the vein tourmalines formed by mixing of the exsolved magmatic-hydrothermal fluids with an external fluid rich in Ca and Mg and having higher δ 11 B than the exsolved magmatic fluids.nificant implications for evolution of magma and volatiles and in fluid-rock interactions, and have long invoked debate regarding their origin (Tilley, 1919;
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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 | 0.002 | 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".