Colombian-style emerald mineralization in the northern Canadian Cordillera: integration into a regional Paleozoic fluid flow regime
Bibliographic record
Abstract
Emerald in the Mackenzie Mountains is hosted in extensional quartz–carbonate veins cutting organic-poor Neoproterozoic sandstones and siltstones within the hanging wall of a thrust fault that emplaced these strata above Paleozoic rocks. Isotopic compositions of water extracted from emerald are typical of evolved sedimentary sulphate brines. Fluid inclusion studies indicate two saline fluid populations: a CO2–N2-bearing, high-salinity brine (20.4–25.8 wt.% NaCl equivalent), and a gas-free, saline brine (7.6–15.3 wt.% NaCl equivalent). Both populations display evidence of post-entrapment volume changes. δ18OVSMOW (VSMOW, Vienna standard mean ocean water) values for emerald, quartz, and dolomite yield averages of 17.3‰ (±0.9), 19.6‰ (±1.5), and 18.1‰ (±1.0), respectively. Dolomite δ13CVPDB (VPDB, Vienna Pee Dee belemnite) averages –6.8‰ (±1.0). Two pyrite samples returned δ34SCDT (CDT, Cañon Diablo troilite) values of 5.1‰ and 11.2‰. Triply concordant mineral equilibration temperatures determined from mineral pair δ18OVSMOW equilibration (quartz–emerald, quartz–dolomite, emerald–dolomite) range from 380 to 415 °C. Depth calculations based on mineral pair isotope equilibration and typical geothermal gradient indicate vein formation at 6–11 km depth. A Re–Os isochron age of 345 ± 20 Ma from pyrite indicates that mineralization was contemporaneous with estimated ages of some northern Cordilleran Zn–Pb occurrences. Emerald mineralization resulted from inorganic thermochemical sulphate reduction via the circulation of warm basinal brines through siliciclastic, carbonate, and evaporitic rocks. These brines were driven along deep basement structures and reactivated normal faults during the development of a trans-tensional back-arc basin during the late Devonian to middle Mississippian. The Mountain River emerald occurrence thus represents a variant of the Colombian-type emerald deposit model requiring thermochemical sulphate reduction.
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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 | 0.002 |
| Science and technology studies | 0.001 | 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) | 0.002 | 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".