Sedimentary provenance analysis by coupled detrital zircon U-Pb, Hf isotopes of the Paleoproterozoic Belcher Group, Nunavut, Canada and implications for sedimentation during the opening and closure of the Manikewan Ocean
Bibliographic record
Abstract
• We present the first detrital zircon U-Pb, Hf isotope record from the Belcher Group. • Provenance analysis shows the lower Belcher Group sourced only the Superior craton. • Provenance analysis shows the upper Belcher Group was sourced more widely. • The Reindeer zone a major source of Omarolluk submarine fan detritus. Coupled detrital zircon U-Pb, Hf isotopic data from the Paleoproterozoic Belcher Group, Nunavut, Canada, are presented to determine maximum depositional ages and sedimentary provenance. We use these data to evaluate potential sediment sources with matching ages and εHf values within a paleogeographic context, to better define the configuration of microcontinents, terranes, and cratons surrounding the Belcher basin during its deposition. The distribution of detrital zircon spectra show that the lower Belcher Group was deposited on the passive margin of the Superior craton, whereas the upper Belcher Group (Omarolluk and Loaf formations) was deposited in syn -orogenic phase, broadly reflecting the opening and closing stages of the Manikewan Ocean, respectively. The lower Belcher Group data show dominant detrital zircon populations between 2825 and 2690 Ma (associated with negative εHf values) with only minor detrital input from sources < 2100 Ma. The dominant grain population is interpreted to be derived from the northeastern Superior craton (>2680 Ma grains), and the Winnipeg River and North Caribou terranes (<2680 Ma grains). The upper Belcher Group shows a dramatic shift in detrital ages from Archean to dominantly Paleoproterozoic, with dominant age peaks between ca. 1920 and 1900 Ma and only minor Archean input that includes 2500 Ma sources that are absent in the lower units. Archean populations document Sask craton-like ages and εHf values, whereas the dominant detrital 1920 to 1900 Ma age population shows positive εHf values that are consistent with being sourced from terranes located in the western Reindeer zone deposited in a submarine fan.
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How this classification was reachedexpand
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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 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) | 0.000 | 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 teacher head, 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".