U-Pb-Hf characterization of the central Coast Mountains batholith: Implications for petrogenesis and crustal architecture
Bibliographic record
Abstract
We present U-Pb geochronologic and Hf isotopic data from 29 plutonic samples within the Coast Mountain batholith, \nnorth-coastal British Columbia and southeast Alaska. Hf isotopic values do not correlate with age or variation in magmatic flux, but rather they increase systematically from west (ε_(Hf)[t] = +2 to +5) to east (ε_(Hf)[t] = +10 to +13) in response to changing country rock assemblages. By comparing our pluton Hf data with previously reported Nd-Sr and detrital zircon characteristics of associated country rocks, we identify three crustal domains in an area where crustal affinity is largely obscured by metamorphism and voluminous pluton intrusion: (1) a western domain, emplaced into continental-margin strata of the Banks Island assemblage; (2) a central domain, emplaced into the Alexander terrane; and (3) an eastern domain, underlain by the Stikine terrane and its inferred metamorphic equivalents. Between the interpreted Alexander and Stikine terranes, there is a zone of variable ε_(Hf)(t) \n(+2 to +13) that coincides with the suture zone separating inboard (Stikine and Yukon-Tanana) from outboard (Alexander and associated) terranes. This variation in ε_(Hf)(t) values apparently results from the structural imbrication of juvenile (Alexander and Stikine) and evolved (Yukon-Tanana) terranes along mid-Cretaceous thrust faults and the latest Cretaceous–early Tertiary Coast shear zone. Shifts in the Hf values of plutons across inferred terranes imply that they are separated at lower- to midcrustal levels by steep boundaries. Correlation between these Hf values and the isotopic character of exposed country rocks further implies the presence of those or similar rocks at magma-generation depths.
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 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".