U-Pb Zircon and Re-Os Isotope Geochronology of Mineralized Ultramafic Intrusions and Associated Nickel Ores from the Thompson Nickel Belt, Manitoba, Canada
Bibliographic record
Abstract
A U-Pb zircon age (1880 ± 5 Ma) has been obtained from a mineralized ultramafic body in the Setting Lake area of the Thompson nickel belt. This crucial new age for ultramafic magmatism in the Thompson belt, in conjunction with the precise age determinations established for the Molson dike swarm (Cross Lake dike, 1883.7+1.7 –1.5 +Ma; Cuthbert Lake dike, 1883 ± 2 Ma) and the Fox River sill (1882.9+1.5 –1.4 +Ma) by Heaman et al. (1986) provides the first direct evidence for the contemporaneous nature of mafic-ultramafic magmatism along the northwest margin of the Superior craton. This magmatic event also appears to be synchronous with mafic magmatism in other parts of the Circum-Superior belt and the Trans-Hudson orogen. Re-Os isotope systematics of mineralized samples from seven deposits that span the length of the belt produce an age similar to the U-Pb zircon age but with a much larger error (1885 ± 49 Ma with an initial γ Os of 4.6). The Os isotope data demonstrate that the source of the Thompson belt ores, including those orebodies hosted in ultramafic rocks and those hosted in pelitic rocks, was dominantly mantle derived. Establishing that Thompson belt magmatism is synchronous with the Molson dike swarm and the extensive Fox River sill has important new exploration implications and requires modification of existing concepts which have presumed that Thompson belt magmatism is significantly older than these other intrusive suites. Also, it would appear that other important Ni and Ni-Cu deposits elsewhere in the Circum-Superior belt and in the Trans-Hudson orogen formed at or near 1.88 Ga, and thus this age could be considered an important and widespread nickel mineralizing metallogenic interval during the Early Proterozoic.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.003 | 0.003 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".