Geochemistry and Metallogeny of Ag-Pb-Zn Veins in the Purcell Basin, British Columbia
Bibliographic record
Abstract
The Mesoproterozoic Purcell Basin in Canada contains three different types of veins: (1) type 1 Pb-Zn-Ag veins are composed of Fe-rich sphalerite, pyrrhotite, galena, freibergite, and pyrite with minor quartz gangue; (2) type 2 Pb-Ag-Cu-Au veins are characterized by galena, pyrite, freibergite, and gold in a quartz gangue; and (3) type 3 Ag-Pb-Zn vein and replacement deposits contain Fe-poor sphalerite, galena, pyrite, and freibergite in a quartz-dolomite gangue that locally replaces host dolostone. The sulfur isotope composition of type 1, 2, and 3 vein and replacement deposits closely reflects their respective stratigraphic positions. Type 1 and 2 veins hosted in lower Purcell sedimentary rocks have light sulfur isotope compositions (−4.8 to +2.5‰) similar to diagenic pyrite disseminated in clastic sedimentary host rocks. Type 3 veins and the replacement deposits hosted in upper Purcell Supergroup rocks have heavy sulfur isotope compositions (8.3–17.2‰) indicative of thermo-chemical reduction of marine sulfate in carbonate host rocks. Quartz from type 1 Pb-Zn-Ag veins has δ 18 O SMOW values ranging from 7 to 17‰, whereas type 2 and 3 vein and replacement deposits have δ 18 O values ranging from 9 to 20‰. The range of δ 18 O values for type 1, 2, and 3 veins is the result of mixing of metamorphic fluids with a δ 18 O value higher than 11.5‰ and an upper crustal fluid with a δ 18 O lower than 1.2‰, in equilibrium with the host rocks during Proterozoic (type 1) and Mesozoic-Cenozoic (type 2 and 3) hydrothermal events. Galena and freibergite lead isotope compositions plot in two groups, consistent with previous studies. Type 1 Pb-Zn-Ag veins have a nonradiogenic lead signature ( 206 Pb/ 204 Pb: 16.322–16.435) and are considered Proterozoic in age. Type 2 Pb-Ag-Au-Cu veins and type 3 Ag-Pb-Zn vein and replacement deposits have a radiogenic lead signature ( 206 Pb/ 204 Pb: 17.842–19.347) and are interpreted to be Mesozoic-Cenozoic in age. Hydrothermal sericite from the type 3 Ptarmigan replacement deposit yields a 40 Ar/ 39 Ar age of 133.1 ± 0.7 Ma, indicating a Cretaceous age for type 3 deposits. Type 1 veins are interpreted to be the result of hydrothermal fluids generated during the Proterozoic East Kootenay Orogeny, whereas type 2 and 3 veins and replacement deposits are interpreted to be the result of Late Cretaceous-Paleocene tectonism.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.028 | 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".