Titanite petrochronology, phase equilibria modelling and the role of amphibole during decompression: Insights from the Shabogamo Domain, central Grenville Province
Bibliographic record
Abstract
• Petrochronological study of a high-P garnet amphibolite. • Multidisciplinary approach results indicate titanite petrogenesis during decompression. • Convergence of multiple thermobarometry methods support the decompression P-T-t path. • Integrated results indicate exhumation of a high-P nappe late during the Grenvillian Orogeny. In this contribution, we present new petrochronological results from samples collected the Shabogamo Domain, of the Grenville Province, Québec, Canada. The Shabogamo domain has a distinct geophysical signature and has been proposed to be linked with the well-studied allochthonous Manicouagan Imbricate Zone. We document a Pressure-Temperature-time (P-T-t) path for an amphibolite sample by combining several approaches including: i) an ordinary least square model able to estimate P-T conditions from amphibole composition using a previously semi-quantitative amphibole thermobarometer ii) titanite petrochronology; iii) phase equilibria modelling; iv) trace element thermometry. We show that single element thermobarometry on titanite and amphibole pairs yield the information necessary to reconstruct a decompression P-T path from peak P-T conditions of 1.8 GPa – 775 °C down to 1.2 GPa – 750 °C and are consistent with results of phase equilibria modelling. Titanite U-Pb geochronology results indicate growth between 987 ± 16 Ma and 969 ± 17 Ma. These results are consistent with U-Pb geochronology on zircon from a dyke that crosscuts the amphibolite and from a deformed leucosome sampled in the domain’s footwall. Zircon from the crosscutting dyke appear to have grown at 985 ± 18 Ma without interaction with garnet, whereas zircon from the deformed leucosomes grew at 972 ± 16 Ma during high-pressure metamorphism. Integrating the results of this study into the regional context outlines the exhumation of a second high-P allochthonous nappe, most likely by ductile extrusion, coeval with the burial of the parautochthonous footwall. This study further supports the growing body of evidence for a major tectonic event during the later phase of the Grenvillian 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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".