Crustal reworking and Eo-Paleoarchean metamorphism of the northern Pikwitonei domain, Superior Province: U-Pb-Hf-TE analysis of 3.9–3.2 Ga detrital zircon
Bibliographic record
Abstract
U-Pb-Lu-Hf-trace element analysis of detrital zircon from two metasedimentary rocks of the Armstrong assemblage in the northern Pikwitonei granulite domain of the NW Superior Province (Manitoba, Canada) are used to explore the Eo-Paleoarchean crustal formation history and zircon petrogenetic processes of the proto-Superior craton. The zircon age spectrum from each sample spans a billion-year period from 3.85 to 2.65 Ga, with a predominant 3.85–3.40 Ga detrital zircon age population. The ca. 3.85 Ga detrital zircon grains from each sample have subchondritic εHf(t) values between −3.9 and − 1.0, consistent with initial crystallization from a suite of late-Hadean to early-Eoarchean protoliths. Semi-continuous Eo-Paleoarchean crustal reworking is subsequently inferred based on the single uniform Hf isotope evolution trend for 3.85–3.20 Ga detrital zircon grains, which is comparable to igneous zircon populations from the Nuvvuagittuq greenstone belt on the eastern shore of Hudson Bay in Quebec. Trace element analysis of detrital zircon grains from both metasedimentary samples indicate the limited presence of detrital metamorphic zircon at 3.67 Ga, 3.5 Ga and 3.4 Ga, which reveal potential metamorphic events within the Eo-Paleoarchean Superior Province. In addition, the detrital igneous zircon grains have trace element compositions consistent with either partial melting of hydrous source rocks or magmatic reworking/assimilation of felsic rocks. The trace element compositions are broadly similar to ca. 3.9–3.2 Ga igneous zircon populations from Acasta and Saglek regions, while demonstrating the importance of calculating initial U concentrations for Hadean – Archean zircon.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| 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 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".