Geology of the Mesoproterozoic Pillar Lake Volcanics and Inspiration Sill, Armstrong, Ontario: evidence of early Midcontinent Rift magmatism in the northwestern Nipigon Embayment
Bibliographic record
Abstract
The Midcontinent Rift System of North America is a ∼1.1 Ga large igneous province comprising mainly flood basalts and intrusive rocks. We present new data for the Pillar Lake Volcanics and Inspiration Sill from the northern edge of the Midcontinent Rift in the northwestern Nipigon Embayment. The Pillar Lake Volcanics comprise a ∼20–40 m thick, flat-lying sequence of mafic pillowed and massive flows, pillowed flow breccia, and hyaloclastite breccia. They are characterized by SiO2 of 52–54 wt%, TiO2 of 1.2–1.3 wt%, and K2O of 0.9–1.1 wt%. They are light rare earth element (LREE) enriched, with La/Smn of 3.0–4.4 with fractionated heavy rare earth elements (HREE) (Gd/Ybn = 1.4–1.7). The Inspiration diabase sill is ≤ 50 m thick and is in direct contact with the underlying Pillar Lake Volcanics. Baddeleyite and zircon data from the Inspiration Sill yield a combined U–Pb upper intercept age of 1105.6 ± 1.6 Ma. The Inspiration Sill is characterized by uniform SiO2 of 52–53 wt%, TiO2 of 1.1–1.2 wt%, and K2O of 0.9–1.2 wt%. Inspiration Sill samples are LREE enriched with La/Smn of 3.2–3.3 and fractionated HREE (Gd/Ybn = 1.6). The Pillar Lake Volcanics are at least 1120 Ma, and perhaps as old as 1130 Ma, and represent an early, thin, and restricted mafic volcanic sequence, largely preserved below the younger Inspiration Sill. The Pillar Lake Volcanics and Inspiration Sill display a marked geochemical similarity, suggesting that they may represent magmatism associated with the earliest stages of Midcontinent rifting.
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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 | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 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".