Volcanic stratigraphy and structural geology of the Boston area, Hope Bay volcanic belt, Nunavut
Bibliographic record
Abstract
The Hope Bay volcanic belt is a mafic volcanic-dominated Archean greenstone belt, in the northeast part of the Slave Structural Province in western Nunavut. The Boston gold deposit, located in the southem part of the Hope Bay belt, is the largest of the known gold deposits in the belt, with a resource of about 1.5 million ounces of gold. The oldest rocks in the Boston area are pillow basalts that host the Boston gold deposit. Stratigraphically overlying these basalts are a succession of sedimentary rocks tbat vary from quartzose feldspathic wacke to argillite. In the upper parts of the succession, these sedimentary rocks are interlayered with intermediate to felsic volcanic sandstones to conglomerates (ca. 2686 Ma). Amygdaloidal pillowed flows overlie the sedimentary rocks, which are in tum overlain by felsic volcanic rocks (ca. 2662 Ma) and argillite. The belt is flanked to the east by late- to post-volcanic tonalite to granodiorite (ca. 2649 Ma) and to the west by late (ca. 2600 Ma) granites. The strata in the Boston area are folded about a large south-plunging synformal anticline, cored by the pillowed mafic flows that host the Boston deposit. Asymmetric folds on the east limb of the main anticline have structurally thickened the sedimentary rocks. Gold mineralization is associated with a complex, anastomosing, high-strain zone that is roughly axial planar to the main anticline and is tentatively interpreted as the latest expression of D, strain. Associated with the high-strain zone is a strong south-plunging stretching lineation, subparallel to the plunge of the anticline fold axis. Accompanying the gold mineralization in the mafic volcanic rocks is a proximal iron-carbonate, quartz and sericite (± paragonite) alteration assemblage that grades out into a chlorite-calcite distal alteration assemblage. Overprinting the main (D,) structural elements are a series of crossfolds (F, ). This folding event resulted in a large embayment of supracrustal rocks into the tonalite-granodiorite on the eastem side of the volcanic belt, and also deforms the gold mineralization and associated alteration at the Boston deposit. The timing of gold mineralization at Boston is grossly similar to what bas been proposed for the northern portion of the belt, at the Doris deposit and in the Madrid area, although the mechanism for gold emplacement is unique in the three areas. Work is underway to constrain the absolute timing of this regional metallogenic event.
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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 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".