Granitic pegmatites in Sri Lanka: A concise review leading to insights and predictions
Bibliographic record
Abstract
Granitic pegmatites can be a source of frustration and confusion. It is thus appropriate to begin with a quick review of basic concepts. Crystallization takes place in the presence of two fluid media; one is a viscous, polymerized silicate magma, and the other is a supercritical aqueous fluid. The two are largely but not completely immiscible. The proportion of aqueous fluid in the mixture progressively increases as the amount of melt diminishes. Pegmatites are of significant economic interest, as they are source rocks of industrial minerals like quartz and the feldspars. These minerals crystallized from the magma, but the feldspars generally become modified by the aqueous fluid. The same applies to accessory minerals that carry Nb, Ta, Zr, Sn and the rare earths. At a late stage, the magmatic fluid phase mixes with cooler, externally derived fluids that bring in elements like Ca and Mg, present in the latest generation of cavity minerals. Frustration arises because the question is recurrent concerning what is magmatic and what is post-magmatic. In terms of tectonic setting, granitic pegmatites may occur in contexts of crustal compression or crustal extension. The pegmatites of Sri Lanka, some of them syenitic and found in all four lithotectonic domains on the island, seem to be unrelated to central plutons. Rather, they are of anatectic origin and members of the NYF family. Some are deformed, but the largest ones are not. Mineralogical and geochemical indicators point to crystallization of the magmas largely in an environment of tectonic relaxation, as in the Grenville collision zone. Important questions remain about the timing of pegmatite emplacement, the interplay of anorogenic magmatism at the end of the Pan-African orogeny, and the role of the mantle in providing heat and fluids that led to localized anatexis of the granulite-grade metamorphic rocks .
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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.006 | 0.004 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".