The geology of the Greenstone orogenic gold deposit, Geraldton, Ontario, Canada: Structural controls, mineralogy, geochemistry, and geochronology
Bibliographic record
Abstract
The Greenstone orogenic gold deposit is located in the Beardmore-Geraldton belt (BGB) along the boundary between the granite-greenstone Wabigoon subprovince and the metasedimentary Quetico subprovince of the Archean Superior craton , Canada. The deposit is hosted by ca. 2700–2694 Ma turbiditic sandstone, banded iron formation , and ca. 2694 Ma feldspar-quartz porphyry, which underwent strong deformation within the 1 km-wide Bankfield-Tombill deformation zone along the southern margin of the BGB. The deformation zone includes folds and cleavage that formed during early D 1 thrust imbrication of the BGB, S-shaped folds and fabrics that formed during D 2 sinistral transpression , and Z-shaped folds, fabrics, and localized shear zones that formed during D 3 dextral reactivation of the deformation zone. Gold mineralization is associated with folded, early-D 1 , quartz-carbonate veins (V 1 ) and with NE- to E-striking, syn -D 2 , tourmaline-quartz veins (V 2 ) as well as quartz-carbonate veins (V 3 ). The V 1 and V 3 veins are surrounded by sericite-carbonate-pyrite ± albite–rutile alteration halos, and the V 2 veins are surrounded by carbonate-tourmaline-pyrite ± pyrrhotite-chalcopyrite alteration halos. Gold was deposited during fluid-rock sulfidation reactions that resulted in the formation of inclusion-poor pyrite with Ni-Co-As primary crystallographic zoning and inclusion-rich pyrite enriched in Au and other metals (Ag-As-Bi-Co-Ni-Pb-Sb-Te). Hydrothermal alteration associated with the deposition of the veins produced a broad, up to 250 m wide, sericite-carbonate alteration envelope, with S, Te, As, W, and Bi as the best pathfinder indicators to gold mineralization. Contrary to previous studies, which attributed the formation of gold deposits in the BGB to late-D 3 , our results suggest that gold was emplaced during early-D 1 and D 2 and involved multiple hydrothermal fluid pulses during several deformation events, as suggested for other major Archean orogenic gold camps associated with major fault zones such as the Timmins and Kirkland Lake camps in the Abitibi subprovince of the Superior craton.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".