THE GARNET - PHOSPHATE BUFFER IN PERALUMINOUS GRANITIC MAGMAS: A CASE STUDY FROM PEGMATITES IN THE POCHO DISTRICT, CORDOBA, ARGENTINA
Bibliographic record
Abstract
Members of the beusite–graftonite series [Mn/(Mn+Fe) between 0.47 and 0.65] appear associated to P-bearing garnet (up to 1.10 wt.% P 2 O 5 in the crystal cores) in two primitive pegmatites of the Pocho district, Cordoba, central Argentina. Elemental maps and electron-microprobe analyses show that garnet has an irregular P distribution, with depleted rims. Textural features of garnet (resorbed margins, isolated relics in beusite, truncated zoning) and similar Mn/Fe values in garnet and beusite indicate that the phosphate formed by destabilization of garnet. The crystallization temperatures of the zones where garnet + beusite occur are 420°C (Tablada I) and 522°C (Cerro Moreno), and the P 2 O 5 content in the melt of the middle intermediate zone at Tablada I is 0.82–0.91 wt.% (estimated using P in feldspars). One possible explanation involves the onset of garnet crystallization before the nucleation of beusite, while the P content of the magma was not buffered. As magmatic evolution progressed, P content increased and eventually reached levels high enough to stabilize mafic phosphates. For some time garnet co-crystallized with beusite; this is reflected by P-depleted zones in garnet. With P build-up, eventually mafic silicates became unstable and were replaced by phosphates. The low activities of F, Li and Na contributed to stabilize beusite. The modest degree of evolution of the pegmatites is indicated by very high Mg content of the phosphates. Beusite has primary inclusions of Mg-rich phosphates, one belonging to the alluaudite group and the other one possibly belonging to the triplite or wolfeite groups. Breakdown of beusite under oxidizing hydrothermal conditions produced, among others, mitridatite and jahnsite-(CaMnMg).
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 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".