FLUID INCLUSION AND ISOTOPE EVIDENCE FOR THE ORIGIN OF THE UPTON Ba-Zn-Pb DEPOSIT, QUEBEC APPALACHIANS, CANADA
Bibliographic record
Abstract
The Upton Ba-Zn-Pb deposit is hosted by the Early Ordovician crinoidal limestone of the Upton Group in the southern Quebec Appalachians. Mineralization consists of barite and minor amounts of sphalerite, pyrite, galena, and chalcopyrite. The paragenesis includes (1) development of secondary porosity and precipitation of subhedral barite, bladed barite, and barite rosettes; (2) precipitation of fracture-filling barite; (3) filling of fractures and remaining voids in the limestone by a sparry calcite; and (4) precipitation of sulfides, quartz, organic matter, and bitumen in the fractures and along the stylolites. Fluid inclusions were studied in pre-barite syntaxial calcite overgrowths, in subhedral and bladed barite, and in post-barite calcite, sphalerite, and quartz. The homogenization temperatures and salinities of the fluid inclusions are greater than 50°C (single-phase liquid inclusions) and 3.9 to 6.9 wt percent NaCl equiv for syntaxial calcite cement, 42.1° to 96.9°C and 4.7 to 8.1 wt percent NaCl equiv for subhedral and bladed barite, 101.4° to 142°C and 5.1 to 7.5 wt percent NaCl equiv for fracture-filling barite, 82.4° to 132.2°C and 18.3 to 19.7 wt percent NaCl equiv for sphalerite, and 121.8o to 164.2oC and 1.7 to 4.2 wt percent NaCl equiv for quartz. Bitumen is present throughout the paragenesis, but primary CH4 inclusions only occur in quartz. H2S- and CH4-enriched gases were detected in barite and calcite by quadrupole mass spectrometry (QMS) analysis, occurring as secondary fluid inclusions. The 87 Sr/ 86 Sr ratios of the barite range from 0.70654 to 0.70781, lower than Early Ordovician seawater. Based on these results and previous C-O-S isotope data, we propose that the Upton Ba-Zn-Pb deposit was formed by mixing of two fluids, a marine water-dominated, SO 2‐ 4 rich fluid, and an 18 O-enriched and 87 Sr-depleted basinal brine, which carried Ba, Zn, and Pb. The reduced sulfur required for the precipitation of sulfides was derived from the thermochemical reduction of sulfate by hydrocarbons. The late precipitation of sulfides after barite may be related to the sluggishness of the sulfate reduction. The mineralization occurred during the Middle to Late Ordovician Taconian orogeny, and tectonic burial and compression is thought to have initiated the circulation of fluids, which would have been channeled through the sedimentary pile along thrust faults and vertical fractures and migrated into the confined crinoidal limestone.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 teacher head, 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".