Auriferous Fluid Evolution and the Role of Carbonaceous Matter in a Saddle‐Reef Gold Deposit: Dufferin Deposit, Meguma Terrane, Nova Scotia, Canada
Bibliographic record
Abstract
Abstract The metaturbidite‐hosted, ∼380 Ma Dufferin gold deposit, Meguma terrane, northeastern Appalachian Orogen (Nova Scotia, Canada) is an orogenic gold deposit with mineralized saddle reef‐type quartz veins hosted by metasandstones and black slates in a tightly folded anticline. Together with native gold inclusions, genetically related hydrothermal carbonaceous material (CM) in veins occurs as pyrobitumen in cavities and along fractures/grain boundaries proximal to vein contacts and wallrock fragments. Integrating several microanalytical methods we document the precipitation of gold via coupled fluid‐fO2 reduction (via interaction with CM) and pH increase. These changes in fluid chemistry destabilized gold bisulfide complexes, leading to efficient Au precipitation from a gold‐undersaturated (0.045 ± 0.024 ppm Au; 1σ; n = 58 fluid inclusions) aqueous‐carbonic fluid (H2O‐NaCl‐CO2 ± N2 ± CH4). The proposed mineralization mechanism is supported by: (a) a complementary decrease in Au and redox‐sensitive semimetals (As, Sb), and increase in wall rock‐derived elements (i.e., Mg, K, Ca, Sr, Fe) concentrations in fluid inclusions with time; (b) a corresponding decrease in the XCO2, consistent with CO2 removal via reduction/respeciation and late carbonate precipitation; and (c) gold embedding in, or on, the surface of CM inside mineralized cavities and fractures. Despite mineralizing fluids transporting low concentrations of Au far from saturation, precipitation of gold was locally evidently high where such fluids interacted with CM, contributing to the overall gold endowment of Meguma deposits. This work re‐emphasizes CM as a potential prerequisite for efficient gold precipitation within the overall genetic model for similar orogenic metasedimentary settings globally where the presence and/or role of CM has been documented.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".