Elbaite-liddicoatite from Black Rapids glacier, Alaska
Bibliographic record
Abstract
Periodico di Mineralogia (2011), 80, 1 (Special Issue), 57-73 - DOI: 10.2451/2011PM0005 Special Issue in memory of Sergio Lucchesi Elbaite-liddicoatite from Black Rapids glacier, Alaska Aaron J. Lussier 1 , Frank C. Hawthorne 1,* , Vladimir K. Michaelis 2 , Pedro M. Aguiar 2 and Scott Kroeker 2 1 Department of Geological Sciences, University of Manitoba, Winnipeg, Canada 2 Department of Chemistry, University of Manitoba, Winnipeg, Canada *Corresponding author: frank_hawthorne@umanitoba.ca Abstract Liddicoatite, ideally Ca(AlLi 2 )Al 6 (SiO 6 )(BO 3 ) 3 (OH) 3 F, is an extremely rare species of tourmaline, found in very few localities worldwide. A large (~ 2 cm in cross section), euhedral sample of tourmaline retrieved from atop the Black Rapids glacier, Alaska, is shown to vary from a light pink elbaite in the core region, average composition (Na 0.4 Ca 0.3□0.3 )(Al 1.75 Li 1.25 ) Al 6 (BO 3 ) 3 (Si 6 O 18 )F 0.4 (OH) 3.6 , to a pale green liddicoatite at the edge of the crystal, (Na 0.3 Ca 0.6 □ 0.1 )(Al 1.0 Li 1.6 Fe 0.2 Mn 0.2 )Al 6 (BO 3 ) 3 (Si 6 O 18 )F 1.0 (OH) 3.0 . Detailed electron-microprobe analysis and 11 B and 27 Al Magic-Angle-Spinning Nuclear Magnetic Resonance spectroscopy show that several substitutions were active during growth, with X □ + Y Al → X Ca + Y Li (liddicoatite-rossmanite solid-solution) and 2 Y Al + X □ → 2 Y M* + X Ca accounting for most of the compositional variation. Throughout the tourmaline, there are instances of reversals in the trends of all major constituents, although few compositional gaps are observed. Most notably, a sharp decline in Ca content from ~ 0.35 to ~ 0.05 apfu (atoms per formula unit) with increasing distance from the core at ~ 2 mm from the crystal edge is followed by a sharp rise in Ca content (to 0.55 apfu), along with (Fe + Mn) content (from 0.01 to 0.35 apfu). In the core region, the origin of the Ca in the tourmaline is not clear; the correlation of Ca and F is consistent with both (1) a melt in which Ca was held as complexes with F, or (2) earlier contamination of the melt by a (Ca, F)-rich fluid. Close to the rim, a dramatic increase in Ca, F, Mn and Fe is probably due to late-stage contamination by fluids that have removed these components from adjacent wallrocks. Key words: liddicoatite; elbaite; tourmaline; late-stage Ca enrichment; pegmatite; zoning; electron-microprobe analysis; Black Rapids glacier, Alaska; 11 B MAS NMR; 27 Al MAS NMR.
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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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".