Correlation of mid-Cretaceous granites with source terranes in the northern Canadian CordilleraLithoprobe Publication 1475.
Bibliographic record
Abstract
This study presents a broad geochemical and isotopic synthesis of mid-Cretaceous granites in the southern Yukon as well as a comparative data set for granites sourced from, and hosted by, accreted terranes in the west through to ancient cratonic rocks in the east. We present data from a traverse perpendicular to the strike of the northern Canadian Cordillera allowing comparison with the growing body of such data derived from the host terranes. Trace elements, specifically the “subduction signature,” allow the discrimination of oceanic verses continental crustal sources. Comparison of isotopic ratios of Sr and, particularly, Nd with published data further refine the correlation of granites with their source terranes. Granites are initially divided based upon their host morphogeological belts, however, our study indicates that the source terranes transcend these traditional boundaries. For Intermontane Belt hosted granites three distinct sources can be identified: an isotopically primitive (Sri, 0.7050; ϵNdT, 2.3 to –1.2), subduction-related source probably associated with the mid-Cretaceous continental margin; an isotopically primitive (Sri, 0.7032 to 0.7035; ϵNdT, 4.2 to 1.4), non-subduction-related source identified as the host Cache Creek terrane; and an isotopically slightly more evolved (Sri, 0.7094 to 0.7101; ϵNdT, 4.5 to –7.3), subduction-related source identified as the host Stikine terrane. Immediately east of the Teslin Tectonic Zone (TTZ), pericratonic Omineca granites (Sri, 0.7032 to 0.7076; ϵNdT, 2.0 to –5.4) do not correlate with their host terranes, but instead show marked similarities with granites immediately to the west of the TTZ suggesting that the same, or similar crustal sources extend further east in the subsurface than previously thought. In the eastern pericratonic Omineca Belt, there is a substantial jump to more evolved isotopic values (Sri, 0.7172 to 0.7354; ϵNdT, –16.6 to –21.7) for granites that extend to the most easterly exposed plutons of the cratonic Omineca Belt. These more isotopically evolved granites correlate with isotopic values for the pericratonic Yukon–Tanana and Cassiar terranes, as well as cratonic North America.
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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 | 0.003 | 0.002 |
| 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) | 0.003 | 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 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".