Reconstructing detailed P-T-t paths of kyanite-bearing, migmatitic metapelites through combined petrochronology and garnet diffusion modelling
Bibliographic record
Abstract
This contribution presents new results of multi-component garnet diffusion modelling (with the software CZGM 1 ) for wellstudied kyanite-bearing migmatitic metapelites from the northern Monashee Complex in the southeastern Canadian Cordillera. In the immediate footwall of the Monashee dcollement, a controversial tectonic boundary, garnet with diameters >2.5 mm preserve prograde zoning defined by bell-shape X sps (Mn endmember in garnet), saddle-shape X prp (Mg end-member) and inverse saddle -shape X grs (Ca end-member). In contrast, zonation for all garnet end-members in grain examined from the immediate hanging wall of the shear zone is flat irrespective of grain size. Plausible Pressure-Temperature-time (P-T-t) paths are well-documented in three published petrochrological studies based on phase equilibria modelling and U(-Th)-Pb geochronology on zircon and monazite. This timing information demonstrates that only the garnet diffusion-parameters derived from Chu&Ague (2015 2 ) are able to model the preservation of the observed X sps profiles in the footwall. The diffusion modelling results indicate a maximal T of <800 o C and implies that the shortest T-t path (<10 Myrs at T >700 o C), plausible within the uncertainties of the petrochronological data, is required to preserve the observed X sps , X prp profiles. Diffusion modelling of hanging wall garnet, in contrast, indicates that a thermal history including peak T = 900 o C, 40 Myrs at T >700 o C and 28 Myrs at T>800 o C are required to completely flatten X grs zoning. The differential results demonstrate that the Monashee dcollement juxtaposes rocks with completely different T-t histories, and, therefore, constitutes a major tectonic discontinuity. Results presented herein further demonstrate that diffusion modelling and petrochronolgy provide the complementary information required to derive a complete P-T-t path of migmatitic metapelites.
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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 | 0.001 | 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 | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.006 | 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".