Seismic and laboratory constraints on crustal formation in a former continental arc (ACCRETE, southeastern Alaska and western British Columbia)
Bibliographic record
Abstract
The ACCRETE project studies continent formation by assemblage of exotic terranes and arc magmatism. A marine‐land seismic profile crosses the terranes with dense sampling and remarkably strong S waves as well as P waves. Unique, high‐quality S‐wave seismic data provide further constraints on interpretation and are used together with new laboratory P‐ and S‐wave velocity measurements (corrected for high temperatures within and at the base of the crust) to make a lithologic and petrologic interpretation. VP/VS ratios indicate three distinct terranes that were assembled to form continental crust. These terranes are the outboard, accreted Alexander‐Wrangellia terrane, the Coast Mountains Batholith (CMB) magmatic arc, and the inboard Stikinia terrane. Below the CMB, VP and VP/VS to a depth of 10–15 km are appropriate for tonalite and diorite. The VP and VP/VS increase with depth indicating that the rocks become more mafic, but VP/VS is not high enough for gabbro. The VP and VP/VS of the lower crust are consistent with a mixture of mafic garnet granulite and restite, whose quartz content lowers the VP/VS ratio below that of gabbro. When corrected for high temperature and uplift due to exhumation, the crust under the CMB exhibits seismic properties of an average continental crust. These results suggest that gabbro could have intruded a metasedimentary pile in the deep crust to cause melting of the metasediments to form intrusions of the CMB, leaving behind a mixture of mafic garnet granulite and sillmanite‐garnet‐quartz restite and generating the deeper part of what becomes an average continental crustal section.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".