Garnet growth during crustal thickening in the Cascades Crystalline Core, Washington, USA
Bibliographic record
Abstract
Garnet Sm–Nd and zircon U–Pb ages, and pressure–temperature–time paths elucidate Late Cretaceous crustal thickening which occurred within magmatic arc rocks of the Insular Superterrane. Voluminous tonalitic magma of the Mount Stuart batholith intruded at <3 kbar into upper crustal sedimentary rocks between 96 and 91 Ma, with initial intrusion prior to garnet growth in the metasedimentary rocks. Arc plutonism then shifted northward as crustal thickening commenced. Initial garnet growth, locally with kyanite and staurolite replacing andalusite, at c. 91 Ma was directly associated with intrusion of granodiorite to tonalite sheets at 7 kbar, north of the Mount Stuart batholith, within the Nason Ridge Migmatitic Gneiss. Subsequent heating and garnet growth, which postdates emplacement of large plutons, occurred between 88 and 86 Ma. This late garnet growth occurred at pressures of 6–8 kbar. The history of garnet growth and intrusion indicates that initial garnet zone and higher temperature metamorphism was restricted to contact aureoles. However, later widespread garnet growth at higher pressure probably resulted from heating as the orogenic wedge approached thermal equilibrium after crustal thickening. We conclude that metasedimentary rocks outside narrow contact aureoles remained at temperatures significantly below those of garnet growth and that the growth of garnet lasted <6 Myr. Heating to temperatures that stabilized garnet after pluton emplacement is compatible with intrusion of arc plutons into an accretionary wedge (Chiwaukum Schist) which was tectonically thickened and/or overthrust causing loading and thermal relaxation.
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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 | 0.001 |
| 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.012 | 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".