Thermal evolution and interaction between impact melt sheet and footwall: A genetic model for the contact sublayer of the Sudbury Igneous Complex, Canada
Bibliographic record
Abstract
The Sudbury Igneous Complex (SIC) and associated Ni‐Cu‐PGE mineralization has been interpreted in terms of a large meteorite impact event. In this study, the thermal relationship between the large cooling melt sheet and the surrounding country rock is examined in terms of its role in an evolving thermal gradient rather than as a passive receptacle for the melt sheet above. Thermal modeling of this environment is undertaken using physical and thermal constraints appropriate to the SIC and assuming heat dissipation from the 2.5‐km‐thick superheated melt sheet (≥1800°C) by either diffusion with zero convection or by rapid convection within the melt sheet. With zero convection, basal cooling produces a solid base, which lowers conductivity such that the immediate footwall rocks reach ≤1000°C, producing partial melting that extends 200 m into the footwall. In a rapidly convecting melt sheet the initial footwall chill is remelted and high temperatures maintained within the sheet close to the contact. This results in higher temperatures being attained in the immediate footwall (1100–1200°C), inducing complete melting of proximal footwall and partial melting to depths of 500 m below the melt sheet. Proximal footwall consists of Paleoproterozoic Huronian basalts, granitoids and sediments, exposed in the south range, overlying Archaean gneisses and granitoids. Total and partial melting of this material early in the cooling history of the melt sheet and the subsequent gravitational accommodation of these melts according to density would produce a basalt‐dominated basal liquid corresponding to the so‐called contact sublayer. The thermal aureole predicted by our models is consistent with that preserved around the north range of the SIC assuming ∼800 m of thermally induced erosion at the contact.
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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 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.002 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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".