Origin of gold mineralization in the Borden Mine and a new tectonic model for the Kapuskasing Structural Zone, Ontario, Canada
Bibliographic record
Abstract
The Kapuskasing Structural Zone (KSZ) containing high–pressure granulites is one of the best exposed mid–to–lower crustal sections in the world. However, the timing and mechanism for its formation/exhumation remain highly controversial. Previous studies of the KSZ and its neighboring Wawa Gneiss Domain (WGD) focused predominantly on Proterozoic brittle deformation in the Ivanhoe Lake Deformation Zone (ILDZ), with tectonic models restricted to political boundaries. In this study, the KSZ and WGD are proposed as a continental metamorphic core complex (MCC) with the high–grade footwall of the former exhumed in comparison to the southern Superior Province, and the latter as the hanging–wall, high–strain listric regional structure. The KSZ exposes granulite–facies ductile sinistral strike–slip shear zones and amphibolite–facies brittle–ductile sinistral and dextral shear zones that predate the ILDZ. \nNeoarchean oblique collision between the Minnesota River Valley terrane and southern Superior Province formed the Pontiac subprovince accretionary prism and equivalents in the “Quiet Zone” by ca. ≥2667 Ma. The formation and exhumation of the WGD and KSZ as a MCC were synchronous with retrograde amphibolite–facies metamorphism by at least ca. ≥2630 Ma. Plutonism and continued transtension, rotation, and related folding continued to ca. 2600 Ma with magmatism ceasing by ca. 2580 Ma. \n The enigmatic Borden Mine (4.17 Mt at an average grade of 6.38 g/t Au) in the Chapleau Belt within the southern KSZ is hosted in sillimanite–garnet–biotite gneisses or schists within metamorphosed mafic and felsic volcanic rocks (with mid–ocean ridge basalt and arc affinities), and banded iron formations. Laser ablation inductively coupled plasma mass spectrometry (LA–ICPMS) analysis of zircon in sillimanite–garnet–biotite gneiss from the Discovery Trench of the Borden Mine yielded three age populations: 2703.9±7.3, 2667.1±7.2 and 2590±17 Ma. The oldest population represents magmatic crystallization that formed the volcanic protolith of the sillimanite–garnet–biotite gneiss, while the latter two record prolonged high–grade metamorphism. Gold mineralization in the Borden Mine most likely formed initially as part of syn–volcanic seafloor hydrothermal alteration and was remobilized throughout prograde upper amphibolite– to– granulite–facies metamorphism during orogenesis and retrograde amphibolite–facies metamorphism during exhumation.
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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 | 0.003 | 0.001 |
| Scholarly communication | 0.002 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".