A New Model for the Coldwell Complex and Associated Dykes of the Midcontinent Rift, Canada
Bibliographic record
Abstract
Abstract Mafic intrusions on the NE shoulder of the Midcontinent Rift (Keweenawan LIP), including Cu–PGE mineralized gabbros within the Coldwell Complex (CC), and rift parallel or radial dykes outside the CC are correlated based on characteristic trace element patterns. In the Coldwell Complex, mafic rocks are subdivided into four groups: (1) early metabasalt; (2) Marathon Series; (3) Layered Series; (4) Geordie–Wolfcamp Series. The Marathon Series are correlated with the rift radial Abitibi dykes (1140 Ma), and the Geordie–Wolfcamp Series with the rift parallel Pukaskwa and Copper Island dykes. U–Pb ages determined for five gabbros from the Layered and Marathon Series are between 1107·7 and 1106·0 Ma. Radiogenic isotope ratios show near chondritic (CHUR) εNd(1106 Ma) and 87Sr/86Sri values that range from –0·38 to +1·13 and 0·702537 to 0·703944, respectively. Distinctive geochemical properties of the Marathon Series and Abitibi dykes, such as Ba/La (14–37), Th/Nb (0·06–0·12), La/Sm (3·8–7·7), Sr/Nd (21–96) and Zr/Sm (9–19), are very different from those of the Geordie–Wolfcamp Series and a subset of Copper Island and Pukaskwa dykes with Ba/La (8·7–11), Th/Nb (0·12–0·13), La/Sm (6·7–7·9), Sr/Nd (5–7·8) and Zr/Sm (18–24). Each unit exhibits covariation between incompatible element ratios such as Zr/Sm and Nb/La or Gd/Yb, Sr/Nd and Ba/La, and Nb/Y and Zr/Y, which are consistent with mixing relationship between two or more mantle domains. These characteristics are unlike those of intrusions on the NW shoulder of the MCR, but resemble those of mafic rocks occurring in the East Kenya Rift. The results imply that an unusual and long-lived mantle source was present in the NE MCR for at least 34 Myr (spanning the 1140 Ma Abitibi dykes and the 1106 Ma Marathon series) and indicate potential for Cu–PGE mineralization in an area much larger than was previously recognized.
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| 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".