The Neoarchean Great Bear Gold Deposit: Evidence for a Second Major Mineralization Event in the Red Lake Greenstone Belt (Superior Craton, Canada)?
Bibliographic record
Abstract
Abstract The Great Bear deposit is a new world-class gold deposit (~6.6 Moz Au) in the Red Lake greenstone belt of the Archean Superior craton in Canada. The deposit is defined by three key zones of mineralization that are located adjacent to an interpreted upper crustal fault (known as the Lithoprobe fault): (1) quartz veining in mafic volcanic rocks in the hinge zone; (2) quartz veining in sulfide-rich argillite horizons in the limb zone; and (3) disseminated and vein-hosted gold within a high-strain zone in the hanging wall of the Lithoprobe fault. The stratigraphy in the hanging wall of the Lithoprobe fault, known colloquially as the Felsic domain, consists of sedimentary rocks (MS1, MS2, and MS3), felsic volcaniclastic rocks (F1), and felsic porphyries (E31 and E32), which were metamorphosed to lower amphibolite facies conditions. We interpret the felsic porphyries, which host a significant fraction of the established gold mineralization, as synsedimentary, emplaced as subvolcanic intrusions and lava domes within an interpreted structural basin. Uranium-lead dating by chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) of magmatic zircons from the synsedimentary quartz-feldspar (QF) porphyry (E31) constrains the age of magmatism to 2710.2 ± 1.2 Ma, which is inconsistent with existing interpretations of the stratigraphy as part of the 2748 to 2742 Ma McNeely sequence of the Confederation assemblage. The E31 porphyry is instead temporally equivalent with a suite of younger syntectonic porphyries and tonalite-trondhjemite-granodiorite intrusions in the Red Lake gold camp. This age also constrains the maximum age of mineralization to <2710 Ma, which is younger than other established gold deposits in the Red Lake greenstone belt, including the giant 2723 to 2712 Ma Campbell-Red Lake deposit, suggesting a second major mineralization event succeeded regional D2 shortening and mineralization in the Red Lake greenstone belt. High-strain zones and structural basins associated with major faults, somewhat akin to the fault-related orogenic gold deposits of the Abitibi subprovince, may therefore represent important first-order targets for exploration in the Red Lake greenstone belt and the adjacent greenstone belts of the Uchi subprovince.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.002 | 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".