Age and Provenance of the Paleoproterozoic Thluicho Lake Group Based on Detrital Zircon SHRIMP Geochronology: A Record of Tectonic Activity in the Southwest Rae Province, Saskatchewan
Bibliographic record
Abstract
Results of a U-Pb detrital zircon geochronological study of the middle Paleoproterozoic Thluicho Lake Group are reported. The Thluicho Lake Group is a succession of coarse clastic rocks that was deposited in continental alluvial basins in the central Zemlak domain of the southwest Rae Province. Over 100 analyses were performed on detrital zircons from two stratigraphically well controlled samples from the Waterloo-Wellington lakes area, 10 km west of Uranium City – the ‘Camel Lake Member’ pebbly arkose of the ‘Powder Lake Formation’ and the ‘Falls Member’ arkose-argillite of the ‘Camsell Portage Formation’. Four analyses of one of the youngest zircons recovered from the stratigraphically higher Falls Member yielded a weighted mean 207 Pb/ 206 Pb age of 1922 ±6 Ma, establishing a new maximum depositional age for the group. This result, together with regional geological relationships, suggests that the group is intermediate in age between development of two major tectonic fronts in this part of the Rae Province; an older, ca. 1.93 Ga east-southeast–trending front that formed at the tail end of Thelon-Taltson orogeny, and a younger, ca. 1.91 to 1.90 Ga northeast-striking front expressed by the Black Bay Fault and associated northeast-striking structures affiliated with the Snowbird Tectonic Zone. The younger age limit for the group may therefore be significantly older than the previously reported minimum age of ca. 1.82 Ga. The distribution of detrital zircon ages defined by the two samples is remarkably similar, with the majority falling within two age ranges: 2750 to 2500 Ma and 2450 to 2250 Ma. The older age range is dominated by ca. 2600 Ma zircons whereas the younger contains two distinct subgroups of ca. 2420 and ca. 2320 Ma. The principal sources of the Thluicho Lake Group were therefore local basement rocks of the Nolan, Taltson, Zemlak (Ena), Beaverlodge, and possibly Train Lake domains. Abundant 2450 to 2250 Ma zircons indicate that the ca. 2.4 to 2.3 Ga Arrowsmith Orogen of the western Rae Province was also a major source of detritus. A few older (>3100 Ma) and younger (<2250 to 1920 Ma) zircons were likely sourced, locally or regionally, within the Rae Province. All told, the bulk of the Thluicho Lake Group detritus came from rocks that can be inferred to have formed the exhumed hinterland of the Taltson mountain belt. A notable feature of the Thluicho Lake dataset is the near-complete absence of 1990 to 1960 Ma zircons, an age range typical of subduction-related plutons of the Taltson Magmatic Zone. The Taltson arc did not supply detritus to the Thluicho depositional basins, supporting the inference that such basins were located in the hinterland of the orogen, which was possibly separated from the foreland by a continental divide. The data reported herein support correlation of the Thluicho Lake and Nonacho groups.
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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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".