Emplacement of metabreccia along the Whistle offset dike, Sudbury: implications for post-impact modification of the Sudbury impact structure
Bibliographic record
Abstract
The Whistle offset dike is a radial dike linked to the ca. 1850 Ma Sudbury Igneous Complex (SIC) in Sudbury, Ontario. It is linked through the funnel-shaped Whistle embayment which formed as a depression along the floor of a superheated impact melt sheet represented by the present-day SIC. The dike consists of metabreccia, quartz diorite, and inclusion-bearing quartz diorite, emplaced in older Archean gneisses and intrusions. Metabreccia has a fine-grained, igneous-textured matrix surrounding Archean basement clasts. It overlaps in major-element compositions (MgO, CaO, SiO 2 ) with the two quartz diorites. The three have similar chondrite-normalized rare-earth element patterns characterized by pronounced negative slopes, i.e., (La/Yb) N = 17–29, and a weak negative Eu anomaly. This suggests that they originated from the same source melts. Metabreccia has higher high-field-strength element (HFSE) ratios, i.e., Gd/Yb, Ce/Yb, Zr/Y, and lower model initial 207 Pb/ 204 Pb isotopic ratios than the two quartz diorites, suggesting that it assimilated more Archean rocks with higher HFSE ratios and lower 207 Pb/ 204 Pb ratios. It formed as SIC melts mixed with melted basement rocks at the SIC-basement contact. This produced a strongly contaminated, inclusion-bearing melt, which drained downward into an offset structure or fault, entrained more fragments plucked from the walls of the fault, and crystallized as metabreccia. Less contaminated quartz diorite was then emplaced in the still-viscous metabreccia during reactivation of the fault caused by isostatic readjustment of the gravitationally unstable crater. More melting, assimilation of clasts, and mixing of SIC melts at the SIC-basement contact produced inclusion-bearing quartz dioritic melts that were emplaced last along the Whistle offset fault.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| 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".