The Triassic-Jurassic corridor of North America: are deep mantle structures a sufficient explanation for intracontinental magmatism?
Bibliographic record
Abstract
Mesozoic intraplate igneous activity is abundant on the Canadian shield and includes multiple kimberlite fields, a province of alkaline magmatism, and individual bodies of kimberlites and ultramafic lamprophyres. Models have variously attributed the emplacement of these intrusions to the influence of Farallon plate subduction, opening of the Atlantic Ocean, or one or several Atlantic hotspots which North American plate is postulated to have drifted over during the Mesozoic. The latter hypothesis relies of the attribution of spatially, temporally and compositionally distributed and diverse magmatic rocks into a poorly defined, age-progressive, ‘corridor’ which may be derived from a common geochemical reservoir. In this study, we aim to test the spatiotemporal association between intraplate igneous activity along this postulated Triassic-Jurassic corridor and several elements of fixed mantle reference frame, such as the Atlantic hotspots and the hypothesised plume-generating zone (PGZ) of the African Large Low Shear Velocity province (LLSVP).We use published geochronological databases containing locations and isotopic ages of the Mesozoic intrusions of North America and published global plate reconstructions to dynamically calculate distances between the loci of intraplate magmatism and features of the upper and lower mantle assuming the latter remained fixed in the mantle reference frame throughout their history. We use GPlates 2.3.0 software package and pygplates 0.36.0 Python library to build the reconstructions and implement our calculations.Results demonstrate that none of the examined mantle features show a consistent association with all instances of intraplate magmatism across the Canadian shield during the Triassic-Jurassic. The coeval kimberlitic magmatism in the western Slave province (Jericho kimberlite field) and Baffin Island (Chidliak kimberlite field) appears to be completely spatially unrelated to any of the examined mantle features. The kimberlite fields of the Superior province (Attawapiskat, Kirkland Lake, Timiskaming) experience emplacements long before and after their passage over the PGZ, but their frequency increases in the PGZ’s vicinity, i.e. 76% of emplacement events in these provinces occur within 200 km of the PGZ’s surface projection.Our results show that intraplate magmatism across many Triassic-Jurassic fields of North America could be initiated independently of the influence of deep mantle structures. Thereby, a geodynamic mechanism nested in the asthenosphere or lithospheric mantle suffices for melt generation in an intraplate setting. However, it cannot be ruled out whether proximity to deep mantle structures is capable of facilitating “shallow” melt generation and emplacement and that deep-seated mantle structures could provide an influx of fluids or thermal energy, increasing melting intensity and volume.
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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 | 0.001 | 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) | 0.002 | 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".