The geochemical evolution of the Logan Igneous Suite, Ontario, Canada: new insights from the Logan Basin and implications for the genesis of the Mesoproterozoic Midcontinent Rift System
Bibliographic record
Abstract
Abstract The 1.1 Ga Midcontinent Rift System (MRS) of North America comprises a series of Mesoproterozoic flood basalts and intrusive rocks emplaced in the Lake Superior region. The mafic rocks preserved on the NW flank of Lake Superior offer insights into the early development of the rift. New geochemical data collected from intrusive rocks in the Logan Basin, coupled with improved constraints on timing relationships between units, allow for a better understanding of the geochemical evolution of intrusive rocks therein. The extensive dataset suggests many previously unrecognized relationships between MRS intrusive rocks, indicating multiple, distinct mantle-source characteristics with highly variable crustal contamination histories, implying a complicated magma plumbing system. The data presented here suggest that five geochemically distinct mantle source regions were involved in the emplacement of the Logan Igneous Suite, each with its own distinct contamination history and perhaps different degrees of partial melting. The geochemical variations could suggest either a progressive, relative depletion in the mantle source over time or heterogeneity of the source region. However, based on the model for MRS magmatism presented here, we suggest that units related to the Logan Igneous Suite were tapping a heterogeneous mantle source that varied over time.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.003 |
| Science and technology studies | 0.002 | 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) | 0.002 | 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".