Lithospheric magnetotelluric imaging in canada: significance to diamond exploration
Bibliographic record
Abstract
Deep magnetotelluric (MT) surveys provide information on thickness, electrical resistivity and tectonic history of Precambrian lithosphere that is relevant to diamond exploration. In regions where lithosphere is electrically resistive, its thickness can be inferred from the observed depth of a conductor at 100 km to 300 km taken as defining the top of the electrical asthenosphere. In some locations high conductivity is observed within the lithosphere and, at depths above the diamond stability field, may be attributed to the presence of graphite. The form of crustal and upper mantle conductors, interpreted with deep seismic information, provides information that can be used to constrain the tectonic history of a region, eg, defining the geometry of past subduction.Surveys in the Slave craton in northern Canada have identified an MT phase anomaly that is coincident with both a diamond-bearing Eocene kimberlite field and an upper mantle geochemical anomaly. The phase anomaly is explained by a conductor, with its upper surface at 80 to 120 km depth and the enhanced conductivity is interpreted as being due to graphite or an interconnected carbon grain-boundary film. In the western Superior Province in central Canada, MT surveys have delineated a mantle conductor at a depth of 130 km. The MT responses define the geoelectric fabric of both the crust and subcrustal lithosphere and indicate that the subcrustal lithosphere is of Archaean age.
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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 | 0.004 |
| Science and technology studies | 0.002 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".