Chemical and boron isotope composition of tourmaline from pegmatites and their host rocks, Sierra de San Luis, Argentina
Bibliographic record
Abstract
ABSTRACT We report chemical and B-isotope analyses of tourmaline from Ordovician S-type granites, an aplite, LCT-type (lithium-cesium-tantalum) pegmatites, and metamorphic rocks of the Conlara Metamorphic Complex (CMC) in Sierra de San Luis, Argentina. For comparison, tourmaline from three LCT pegmatites in the adjacent Pringles Metamorphic Complex was also studied. Metamorphic tourmaline from the CMC has intermediate schorl–dravite compositions, with variable Fe# [100 * Fe/(Fe + Mg)] from 32 to 79. The δ11B values range from –14.8 to –8.9‰, which are typical values for continental metasediments and granites, ruling out a marine origin for the tourmalinite protoliths. Tourmaline from the S-type granites and aplite is more homogeneous, with Fe# from 48 to 60. The δ11B range (–14 to –9.8‰) of granitic tourmaline is within that of the metamorphic tourmaline, supporting the idea of boron recycling in the CMC during partial melting to form the granites. Tourmaline from CMC-hosted pegmatites is compositionally diverse and we distinguished three groups based on Fe#: Group 1: 42 to 50, Group 2: 50 to 62, and Group 3: 62 to 93. Regardless of strong variations in Fe#, tourmaline from all pegmatites in the CMC has δ11B values from –10.3 to –7.8‰. These values overlap with the range of related granites but are about 2 permil higher, which we attribute to crystallization of 10B-enriched minerals (mica and tourmaline) in the evolved magma from which the pegmatites formed. Pegmatites from the Pringles Metamorphic Complex contain tourmaline with a similar overall range of Fe# (45 to 84) as in the CMC but lower δ11B values (–13.2 to –11.2‰).
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.000 | 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) | 0.001 | 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".