Mineralogy of a cuspidine–hiortdahlite–wollastonite skarn associated with the Sierra La Vasca alkaline complex, Mexico
Bibliographic record
Abstract
Abstract The Tertiary Sierra La Vasca intrusive complex of the Mexican Eastern Alkaline Province consists of diverse alkaline-to-peralkaline granitoids and syenites and is a rare example of silica oversaturated peralkaline magmatism characterized by eudialyte. The intrusion of these peralkaline rocks into Cretaceous carbonate country rocks resulted in the development of a unique cuspidine, Zr-bearing cuspidine, hiortdahlite and wollastonite exoskarn. This study is focussed on a eudialyte-bearing vein and accompanying banded exoskarn which illustrates the unusual skarn-forming metasomatic effects of Zr mobilization. The skarn consists of six mineralogically distinct zones: (1) a parental Nb-poor eudialyte-bearing quartz granitoid vein; (2) a region of eudialyte pseudomorphed by intergrown Zr-sorosilicates; (3) an andradite–cuspidine–hiortdahlite–wöhlerite zone; (4) a zone of skeletal-to-prismatic cuspidine plus wollastonite which is transitional to zone (5); a coarser grained and heterogeneous zone consisting of complex intergrowths of tabular and prismatic cuspidine–hiortdahlite solid solutions, wollastonite, fluorite, apatite and rare calcite; (6) a contact calcite marble lacking any metasomatic silicates, phosphates or fluorite. Skarn formation was the result of alteration of eudialyte and separation of Si-rich hydrothermal fluids with high F/H 2 O ratios from the parental Si-oversaturated peralkaline magma and subsequent infiltration of Si–Zr–REE–P-bearing fluids into the country rock carbonates. Zircon was probably transported as Zr-fluoride and chloride complexes and the acidic fluids reacted with calcite to form cuspidine–hiortdahlite solid solutions and wollastonite as the principal skarn minerals. All of the Si required to form this unique skarn assemblage was derived from the hydrothermal fluids as the country rocks do not contain Si-bearing minerals. Skarn formation is considered to have occurred at temperatures below 500°C.
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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 | 0.001 | 0.000 |
| 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".