Compositions of Fluid Phases and Quartz Solubility in H<sub>2</sub>O-NaCl-CO<sub>2</sub> Fluids in Mesothermal Gold Deposits
Bibliographic record
Abstract
Hydrothermal fluids in orogenic and intrusion-related gold deposits are dominated by H2O-NaCl-CO2 fluids.In this study, thermodynamic modeling was conducted to constrain the fluid properties and quartz dissolution/precipitation behavior under single-and two-phase conditions in the H2O-NaCl-CO2 system at temperatures of 300 to 500 ºC and pressures of 0 to 3.5 kbar.Increasing CO2 and/or NaCl contents shift the solvus to higher pressures and temperatures, expanding the pressuretemperature region of L+V immiscibility.Isopleths of CO2 content in coexisting, immiscible vapor and liquid confirm that fluid phase separation cannot produce fluids of pure CO2 through the studied P-T-x ranges.Rapid drop in pressure is an efficient mechanism driving fluid immiscibility at specific ranges of temperature and composition, producing liquid-rich inclusions with relatively high salinity, and vapor-rich inclusions with relatively low CO2 content.In contrast, immiscibility driven primarily by cooling will take place only in the case of initial fluids with relatively high CO2 contents (>10 mol.%), and gives rise to diverse fluid inclusion types: producing a liquid with low salinity and low CO2 contents and a high-density vapor with moderate to high CO2 contents up to ~65 mol.%.Quartz solubility in the H2O-NaCl-CO2 fluids shows strong dependence on temperature, pressure, and CO2 content.Solubility of quartz generally decreases with decreasing temperature and pressure, and increasing CO2 content both in the single-and two-phase fluids, but exhibits retrograde behavior in the L+V field and near the phase boundary between single-phase and L+V.In orogenic gold deposits, decompression-induced quartz precipitation during pressure fluctuation is dominant in bedding-parallel shear veins.Fault-related extensional veins are associated with initial decompression-induced quartz precipitation and subsequent cooling-dominated deposition.
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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 | 0.000 | 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) | 0.000 | 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".