Detrital zircon U-Pb and ΕHf signature of the Yukon-Tanana terrane in Yukon, Canada
Bibliographic record
Abstract
The Yukon-Tanana terrane consists of pre-Late Devonian metasedimentary rocks of the Snowcap Assemblage that are overlain by multiple unconformity bounded sequences of arc-related igneous and clastic rocks divided into the Upper Devonian-Lower Mississippian Finlayson assemblage, Middle Mississippian-Lower Permian Klinkit assemblage. The YTT arc rocks formed outboard of coeval oceanic assemblages of the Slide Mountain terrane. This study presents new U-Pb and Hf isotopic data from zircon to better characterize these assemblages. Magmatism in the Finlayson assemblage initiated by 367 Ma and defines the peak of felsic magmatism in the YTT arc. Subsequent magmatic cycles show diminished signals in the detrital record with an increase to more mafic magmatism and a trajectory towards juvenile εHf values by early Pennsylvanian time. The detrital record of YTT in Yukon (YTTn) differs from that observed in YTT rocks in southeastern Alaska (YTTs). Magmatism in YTTs precedes that in YTTn, extending from 400 to 365 Ma and defining a trend from juvenile to evolved εHf signatures. There is a brief period of similarity in evolved magmatism at 350-360 Ma that may indicate interaction between YTTn and YTTs prior to shutoff of arc magmatism in YTTs.
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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 | 0.002 |
| Science and technology studies | 0.002 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".