Synvolcanic Au-Ag±Cu-Zn-Pb massive sulphides, veins and disseminations of the Westwood deposit, Abitibi greenstone belt, Québec
Bibliographic record
Abstract
The Westwood deposit (3.715 Moz of Au) includes three distinctive mineralized corridors stacked from north to south: 1) Zone 2 Extension, 2) North Corridor and 3) Westwood Corridor. The Zone 2 Extension consists of cm- to dm-wide pyrite- and chalcopyriterich quartz veins and dissemination zones whereas the North Corridor consists of cm- to dm-wide quartz-pyrite-chalcopyrite ± sphalerite veins and disseminations as well as thin, semi-massive to massive sulphide veins. The hydrothermal envelopes of these two corridors are slightly discordant to the stratigraphy and main foliation. Finally, the Westwood Corridor consists of discontinuous stratabound polymetallic semi-massive to massive sulphide lenses, veins and disseminations. The Westwood mineralized corridors are part of the Doyon-Bousquet-LaRonde mining camp and are hosted in metavolcanic rocks of the Bousquet Formation (2699-2696 My), which forms a steeply south-dipping, east-trending homoclinal sequence facing south. The study area is metamorphosed to greenschist-amphibolite facies transition and deformation is heterogeneously distributed with high strain corridors typically localized at lithological contacts and within synvolcanic alteration zones. The Warrenmac massive sulphide lens (Westwood Corridor) is characterized by pyrite-sphalerite-chalcopyrite ± galena-pyrrhotite and is overlain by a highly transposed stringer zone, which are both anomalous in Sn, Hg, As and Sb. Sericite, quartz, biotite, chlorite and Mn-garnet define the metamorphosed proximal alteration assemblage whereas an aluminous alteration assemblage (staurolite, andalusite, kyanite) is preferentially developed at depth (> 1.5 km). Mapping of the Warrenmac discovery outcrop revealed that felsic volcaniclastic rocks hosting the massive sulphide lens are intruded by low-permeability mafic sills which acted as cap rocks for ascending hydrothermal fluids. Moreover, synvolcanic alterations discordant and strongly transposed into the main foliation combined with the presence of abundant sulphide fragments within felsic volcaniclastic breccias suggesting a synvolcanic origin for the Au mineralization. Zone 2 Extension and Doyon mine mineralization (~1.5 km west of Westwood) are interpreted to be genetically related to the synvolcanic Mooshla pluton whereas Westwood and North corridors have a VMS-type origin and are located on the same stratigraphic horizon as LaRonde Penna mine 20 North lens to the east. U/Pb zircon dating suggest that the three mineralized corridors might have been formed in less than 2 My. The Westwood deposit therefore represents a unique opportunity to test the hypothesis of a continuum between vein-type mineralization associated with a synvolcanic intrusion and auriferous massive sulphide lenses, and thereby contribute to a better understanding of Archean auriferous magmatic-hydrothermal systems. Metallogenic continuums are well documented in younger geological environments such as telescoped porphyry-epithermal systems.
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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 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.006 | 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".