Abstract: Investigation of a late Proterozoic mafic sill and its environs–Cape St. Francis, Newfoundland
Bibliographic record
Abstract
The aim of this study is to characterize a mafic sill and its environs in the vicinity of Cape St. Francis, Newfoundland, and then investigate its implications for late Proterozoic bimodal magmatism in the Avalon Zone of the Appalachian orogenic belt. The sill defines a prominent ridge, approximately 600 m long and 87 m thick and is commonly bounded by northwesterly dipping arkosic sandstones and overlying sequences of pillow basalt and pillow breccia. Field observations, however, indicate that the sill locally cuts the pillow basalts near the westerly boundary of the ridge. To the north, cogenetic rhyolite domes puncture the sandstone. The sill itself has a bulk trachyandesite composition with a layered appearance, which is characterized by thin (1–2 mm) seams that are parallel to contacts and closest together near contacts. In some cases the sill has a banded appearance due to cm-scale leucocratic and melanocratic layers. An examination of the millimeter scaled variations of mineralogy within the layers using the Scanning Electron Microscope work indicated that there were two types of seams. One type has a highly silicic composition while the other has the same composition but is finer grained than the layers in which it occurs. Further examination of these layers will be completed using Microprobe analysis. Detailed groundbased magnetic and elevation surveys were carried out to build a three dimensional model of the sill morphology and extent below the surface. Regional geophysical surveys including vertical magnetic gradient, total magnetic field, and VLF-EM total field were analysed and compared with the ground magnetic survey. Geochemical analysis for major and trace elements has been completed on rock units that include basalt, rhyolite, arkosic sandstone, trachyandesite, and silicic seams.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.002 | 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".