Resolving Paragneiss Provenance at Grollier Lake in the Athabasca Granulite Terrane, Western Canadian Shield
Bibliographic record
Abstract
U-Pb crystallization ages of metamorphic and detrital zircons from all three paragneiss samples fall into the range of ca. 1.85-2.59 Ga, excluding two much older grains. Evidence suggests that the paragneiss of Grollier Lake record deformation exclusively from the Taltson and Trans-Hudson orogenies. It is apparent from geochronological data that the Taltson orogeny played an exceedingly larger role in the deformation of these rocks than the Trans-Hudson. Deposition of the paragneiss protoliths most likely culminated between ca. 2037-1994 Ma with metamorphism ceasing by 1852.1 ± 11.1 Ma. The oldest overgrowth considered to be concordant is 1994 ± 12 Ma and interpreted to represent the first signature of burial facilitated by the Taltson orogeny. U-Pb crystallization ages ranging from ca. 1872-1900 Ma can be attributed to metamorphisms from both the late Taltson or early Trans-Hudson orogenies given that the transition between these events is hard to delineate. Zircons dated > ca. 2.04 Ga are detrital in origin with U-Pb crystallization ages for these grains possibly being discordant as supported by the concordia diagrams. However, these ages can still be explained by provenance from sources such as the ca. 2.17-2.13 Ga Rutledge River basin to the west of Grollier Lake, and the ca. 2.3 Ga Arrowsmith subduction-related plutons north of Lake Athabasca. Older zircons (2955.6 ± 10.7 Ma and 3078 ± 13.9 Ma) in the migmatitic paragneiss are inferred to be inherited from Neoarchean and early Paleoproterozoic crust below. It is possible that rocks of the lower structural levels will record deformation from the Arrowsmith orogeny.
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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 | 0.003 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.002 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".