Wrangellia flood basalts in Alaska: A record of plume‐lithosphere interaction in a Late Triassic accreted oceanic plateau
Why this work is in the frame
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Bibliographic record
Abstract
The Wrangellia flood basalts are part of one of the best exposed accreted oceanic plateaus on Earth. They provide important constraints on the construction of these vast submarine edifices and the source and temporal evolution of magmas for a plume head impinging beneath oceanic lithosphere. Wrangellia flood basalts (∼231–225 Ma) extend ∼450 km across southern Alaska (Wrangell Mountains and Alaska Range) where ∼3.5 km of mostly subaerial flows are bounded by late Paleozoic arc volcanics and Late Triassic limestone. The vast majority of the flood basalts are light rare earth element (LREE) ‐enriched high‐Ti basalt (1.6–2.4 wt % TiO 2 ) with uniform ocean island basalt (OIB) ‐type Pacific mantle isotopic compositions (ɛ Hf (t) = +9.7 to +10.7; ɛ Nd (t) = +6.0 to +8.1; t = 230 Ma). However, the lowest ∼400 m of stratigraphy in the Alaska Range is LREE‐depleted low‐Ti basalt (0.4–1.2 wt % TiO 2 ) with pronounced negative high field strength element (HFSE) anomalies and Hf isotopic compositions (ɛ Hf (t) = +13.7 to +18.4) that are decoupled from Nd (ɛ Nd (t) = +4.6 to +5.4) and displaced well above the OIB mantle array (Δɛ Hf = +4 to +8). The radiogenic Hf of the low‐Ti basalts indicates involvement of a component that evolved with high Lu/Hf over time but not with a correspondingly high Sm/Nd. The radiogenic Hf and HFSE‐depleted signature of the low‐Ti basalts suggest pre‐existing arc lithosphere was involved in the formation of flood basalts that erupted early in construction of part of the Wrangellia plateau in Alaska. Thermal and mechanical erosion of the base of the lithosphere by the impinging plume head may have led to melting of arc lithosphere or interaction of plume‐derived melts and subduction‐modified mantle. The high‐Ti lavas dominate the main phase of construction of the plateau and were derived from a depleted mantle source distinct from the source of MORB and with compositional similarities to that of ocean islands (e.g., Hawaii) and plateaus (e.g., Ontong Java) in the Pacific Ocean.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 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) | 0.003 | 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 it