Bibliographic record
Abstract
The Sudbury Structure, Ontario, is the remnant of a 1.85 Ga old impact crater, 200--250 km in diameter. Erosion and tectonism have affected the Sudbury Structure and resulted in considerable brittle and ductile deformation, and the removal of the surface expression of the crater structure and all exterior deposits typical of many terrestrial impact structures. However, substantial amounts of the interior deposits, including the craterfill products, have been preserved within the Sudbury Basin. Although most workers acknowledge an impact origin for the Sudbury Structure, the origin of the Sudbury Igneous Complex (SIC), located inside the Sudbury Structure, remains controversial. The objectives of this study are to elucidate the division of the SIC into lithologically separate phases and to understand their relation to impact and endogenic igneous processes by using physical, chemical and computer methods, and to model the genesis of the SIC. The SIC is a 2.5--3.0 km thick, ∼60 x 27 km elliptical igneous-rock body, consisting of four major lithologies (top to base): granophyre, quartz gabbro, norite, and the so-called contact sublayer. All these lithologies are continuous across the complex, except for the contact sublayer. Modal compositions reveal that the current nomenclature is improper. According to the IUGS classification, "quartz gabbro" samples should be classified as quartz monzogabbros and "norite" samples as quartz gabbros or quartz monzogabbros. In view of these observations, an updated terminology is proposed (top to base): upper unit, transition zone, middle unit, lower unit, and contact sublayer. Gradational mineralogical and geochemical variations between the SIC lithological units are evidence of a single melt system for the SIC. The occurrence of primary hydrous minerals, deuteric alteration, and abundant micrographic and granophyric intergrowths demonstrate that this melt was rich in H 2O. The intergrowths and other far-from-equilibrium textures are likely due to rapid crystallization as a result of a large undercooling caused by the exsolution of a volatile phase. The SIC differs from other known terrestrial impact melt sheets only by its great thickness and its chemical layering. It is concluded that the SIC is a differentiated impact melt sheet, the only one identified on Earth to date.
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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 | 0.002 | 0.003 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".