A Tale of Two Kimberlite Fields: the contrasting resistivity structure beneath northern Alberta kimberlites and tectonic implications from magnetotellurics
Bibliographic record
Abstract
New long-period magnetotelluric data have been collected to improve the spatial coverage and resolution of the existing resistivity model for Northern Alberta. This area hosts two diamondiferous kimberlite fields: (1) the well-endowed Buffalo Head Hills and (2) the diamond-poor Birch Mountains, which are both part of the regional kimberlite magmatism that occurred across North America during the Cretaceous. The updated 3-D resistivity model shows different structures beneath both fields, with a major conductor, the Birch Mountains Conductor (BMC) and resistive lithosphere underlying Birch Mountains and Buffalo Head Hills, respectively. The BMC is attributed to the presence of partial melt and a lithosphere that has undergone erosion, thinning, and destruction of the diamond window. The quantity of partial melt required to explain the resistivity of the BMC is consistent with teleseismic constraints, and the elevated temperatures and alkaline intrusions inferred from geochemical data from Birch Mountains intrusions. In comparison, the Buffalo Head Hills lithosphere is highly resistive and unmodified, which would have preserved the diamond window. This would explain the contrasting diamond potential between the fields. The resistivity structure and the kimberlite fields are evaluated with respect to the tectonic models invoked to explain Cretaceous kimberlite magmatism in North America. Both favor the presence of a west-dipping subducting slab located in the transition zone undergoing devolatilization and generating upwelling and magmatism beneath North America. This model is similar to the big mantle wedge model of East Asia, with the alkaline-affinity intrusions there being analogous to the kimberlite magmatism in North America.
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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 | 0.000 | 0.000 |
| 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".