A bimodal volcanicplutonic system: the Zarembo Island extrusive suite and the Burnett Inlet intrusive complex
Bibliographic record
Abstract
The Zarembo Island volcanic rocks and the Burnett Inlet plutonic complex in central southeastern Alaska were investigated to determine if they are genetically related. The Zarembo Island volcanic suite consists of basalt, andesite, and rhyolite lava flows, which exhibit features that suggest simultaneous eruptions of mafic and felsic lavas. Five kilometres to the southeast, the broadly layered Burnett Inlet plutonic complex consists of gabbrodiorite and granite plutons that also show characteristics of contemporaneous mafic and felsic magmatism. These bimodal volcanic and plutonic rocks are similar in age, ranging from 18.5 to 21.5 Ma. Both suites show a gap in silica concentration between 60 and 65 wt.% and have similar major, trace, and rare-earth element composition. Both suites also show igneous layering, either as interlayered basalt and rhyolite flows or as alternating gabbro and granite sheets. Additionally, both groups contain magma mingling and mixing textures, including mafic enclaves in felsic members and quartz xenocrysts rimmed by clinopyroxene in enclaves. These characteristics suggest that the Burnett Inlet intrusive complex and the Zarembo Island volcanic suite represent an eroded, shallow-level plutonic center and its eruptive cover. The style of volcanism and the bimodal nature of magmatism suggest that igneous activity occurred during crustal extension and thinning that accompanied strike-slip tectonic motion in southeastern Alaska during the Tertiary. The volcanicplutonic rock associations now exposed at the surface indicate that at least 7° of post-20 Ma crustal tilting has affected the region and can help to explain aberrant paleomagnetic poles in mid-Cretaceous intrusions of the Cordillera Coast belt.
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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 | 0.000 |
| 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 | 0.000 |
| 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".