Chronologic constraints on the tectonic evolution of the Wilson Lake terrane of the Grenville Province, Canada
Bibliographic record
Abstract
the Grenville Orogen in North America. Many of these terranes record evidence of two orogenies: the Labradorian Orogeny at ca. 1710-1600 Ma, and the Grenville Orogeny at ca. 1080-980 Ma. The rocks in the Wilson Lake terrane are interpreted to have been subjected to peak pressures of ~0.95 GPa and ~930°C during the Labradorian Orogeny (Korhonen et al., in prep., Stability of sapphirine + quartz in the Wilson Lake terrane: calculated equilibria in NCKFMASHTO). The final amalgamation of the Wilson Lake terrane over the underlying Parautochthonous Belt is interpreted to have occurred during the Grenville Orogeny, when the terrane was subjected to a lower-T (500-350°C) overprinting. However, petrologic and chronologic evidence for the Grenville orogeny is limited in the Wilson Lake terrane. Here we present results from a monazite chemical (U-Th)-Pb chronologic study in order to provide constraints on the metamorphic history of the Wilson Lake terrane. Monazite was analyzed in samples of orthopyroxene + sillimanite + quartz bearing and sapphirine + quartz bearing gneisses from throughout the Wilson Lake terrane. These samples contain two distinct populations of monazite: 1) a population of large (up to ~500 µm) monazite exhibits distinct core and rim zoning in yttrium X-ray compositional maps, and occurs predominately in the melanosome of the rocks, and 2) a population of smaller (up to ~50 µm) unzoned monazite rarely occurs in quartz-rich layers of the rocks. In a majority of the melanosome-hosted monazite, (U-Th)-Pb chemical ages yield cores and rims with statistically similar Labradorian ages of ca. 1705-1675 Ma. However, one sample from the middle of the terrane yields monazite grains with Labradorian age cores (ca. 1710 Ma) and post-Labradorian rims (ca. 1590 Ma). Monazite from the second, quartz-hosted population in one sample from the leading edge of the Wilson Lake terrane yields a Grenvillian age of ca. 1055 Ma, potentially supporting the hypothesis for Grenvillian emplacement of the Wilson Lake terrane
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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 | 0.002 |
| 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) | 0.003 | 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
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