Geochronology and geochemistry of deeply buried basement along the western Superior Craton and eastern Trans-Hudson Orogen (North America)
Bibliographic record
Abstract
Abstract The Paleoproterozoic Trans-Hudson Orogen of North America resulted from the amalgamation of the Wyoming, Hearne, Sask, and Superior cratons. Previous work has constrained the timing of terminal collision of the Hearne, Sask, and Superior cratons to ca. 1.83–1.80 Ga (Canadian Shield), and the Wyoming and Superior cratons to 1.78–1.72 Ga (Black Hills, South Dakota, USA). More than 1200 km separate the Canadian Shield and Black Hills, between which there is no crystalline basement exposure due to Phanerozoic sedimentary cover, and limited data exist. This study presents U-Pb zircon geochronologic, major and trace element geochemical, and isotopic (εHf zircon and εNd whole-rock) data from two basement drill cores ~3000 m deep collected along the western edge of the Superior Craton and eastern margin of the Trans-Hudson Orogen overprint, between the Canadian Shield and Black Hills. The western core contains ca. 1.83 Ga mafic gneiss with juvenile isotopic [εHf(i) and εNd(i)] geochemical signatures and an amphibolite-grade metamorphic overprint. The eastern core contains ca. 2.7 Ga granitic gneiss with trace element and juvenile isotopic geochemical signatures that are consistent with granitoids from the western Superior Craton. Paleoproterozoic (ca. 1.79–1.77 Ga) granitoid intrusions occur in both cores that display trace element signatures suggestive of origination in a continental arc setting. Isotope geochemistry plus inherited zircon populations indicate that intrusive granitoids are mixtures of juvenile Paleoproterozoic mantle and recycled crustal material. The ca. 1.79–1.77 Ga granitic magmatism observed falls chronologically between the terminal Hearne, Sask, and Superior collision and the Wyoming and Superior collision, and the data presented herein represent a step toward better understanding the buried southern Trans-Hudson Orogen.
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 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".