Late-alpine five-element mineralization in the Punta Corna vein system (Western Alps): evolution of methane-bearing crustal fluids and their role to arsenide precipitation and ore-deposit metallogeny
Bibliographic record
Abstract
The Punta Corna vein system (PC), located within the Western Alpine meta -ophiolites, is characterized by a five-element vein type mineralization including Fe-Co-Ni arsenides preceded and followed by a typical base-metal sulfide mineralization, comprising tetrahedrite, chalcopyrite, pyrite and galena. Three distinct hydrothermal stages were recognized: Sulfide stage I, Arsenide stage and Sulfide stage II. Microthermometric analysis of fluid inclusion assemblages from Sulfide stage I allowed to constrain fluid A (surface-derived, sulfate-bearing, ∼27.3 wt% total salinity and 140 °C homogenization temperature) and fluid B (deep-seated, methane-bearing, 18.8 wt% total average salinity and 163 °C homogenization temperature). The Arsenide stage is characterized by the presence of fluid C (deep-seated, ∼19 wt% total average salinity and 156 °C homogenization temperature) and fluid D (deep-seated, ∼13 wt% total average salinity and 230 °C homogenization temperature). Fluids B and C are inferred to represent the same fluid, with and without methane, respectively. The absence of methane in fluid C is interpreted as its consumption during arsenide formation by reduction. This detailed fluid inclusion study revealed evidence of pre-ore methane, which has been proposed as a reducing agent, important in the formation of five-element mineralization. This finding has two important implications: (i) it constrains the shift from a hydrothermal system precipitating base metal sulfides to a five-element one through the mixing of a metal-bearing fluid and a highly reduced methane-bearing fluid, and (ii) it records the presence of an oxidized sulfate-bearing brine and the reduced-metal bearing fluid in the crustal rocks, which mixed and thus formed the five-element mineralization. Crucial to this process is the role of late-Alpine brittle tectonics, which, through the development of two main fault systems, enhanced rock permeability allowing the input of different fluids in the active hydrothermal system.
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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 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".