Fluid inclusion constraints on the origin of the brines responsible for Pb–Zn mineralization at Pine Point and coarse non‐saddle and saddle dolomite formation in southern Northwest Territories
Bibliographic record
Abstract
Abstract The Pine Point region is a classic metallogenic mining camp that produced over 58 million short tons of Zn–Pb ore from approximately 40 base‐metal mineralized deposits hosted by Middle Devonian carbonates. The ore deposits are localized in paleokarstic features found in the epigenetic ‘Presqu'ile’ dolomite that preferentially replaced some of the upper barrier limestones. The main ore‐stage sulfides include galena, sphalerite, marcasite, and pyrite. A bulk fluid inclusion chemistry study was carried out on sulfide, coarse non‐saddle and saddle dolomite and calcite samples from the Pine Point and Great Slave Reef deposits, and unmineralized coarse non‐saddle and saddle dolomite samples from Hay West, Windy Point and Qito areas. Molar Cl/Br ratio data from Pine Point indicate the presence of four fluids at different stages of the paragenesis. The fluids trapped in sulfides and ore‐stage dolomites predominately consist of a Br‐rich fluid with a composition similar to that of evaporated seawater (fluid A), and a very Br‐enriched fluid of unknown origin (fluid B). Both these fluids are CaCl2–NaCl (Na to Ca ratios of 1:10)‐rich brines and have compositions unlike the modern formation waters in the Devonian aquifers in the basin today. A third, relatively Cl‐rich (or Br‐poor), fluid (fluid C) was identified in two samples and may have acquired some chlorinity by dissolving halide minerals. Mixing between the Br‐rich fluid A and a dilute fluid also occurred in the later stages of the paragenesis, resulting in the formation of calcite and native sulfur. Saddle and coarse dolomites not associated with significant sulfide mineralization have a narrow range of halogen compositions similar to fluid A. There is no evidence of fluid B or C in the unmineralized samples. Relative to a modern‐day seawater compositions all the fluids have had some modification of their cation compositions. There is some weak evidence for interactions with clastic units or crystalline basement rocks. It is also possible however, that the evaporative brines could have formed from a relatively CaCl2‐rich, NaCl‐depleted Devonian seawater, unlike the composition of modern‐day seawater.
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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 | 0.001 | 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".