Cathodoluminescence and trace-element chemistry of quartz from Sudbury offset dikes: Observations, interpretations, and genetic implications
Bibliographic record
Abstract
Abstract Offset dikes, radial and concentric fractures infilled with quartz diorite, are important hosts of Ni-Cu-PGE mineralization in the Sudbury area. To better understand their emplacement and evolution, the cathodoluminescence (CL) and trace-element chemistry of quartz were examined in quartz diorite from the Foy, Trill, Whistle, Hess, Parkin (North Range), and Copper Cliff (South Range) offsets. Although the potential causes of the CL response in quartz are considered, the primary focus was the qualitative textures and patterns, as these can provide valuable paragenetic information. Quartz from the North Range displays a strong blue luminescence dominated by homogenous and sharply zoned CL patterns, while that from the Copper Cliff offset displays a weak CL response. Locally recrystallized granoblastic quartz shows diffuse concentric zoning and other heterogeneous CL patterns. Trace-element EPMA-WDS analyses indicate that quartz from the Foy, Trill, and Whistle offsets is enriched in Al (30–600 ppm) and Ti (50–520 ppm) as compared to Fe (<25–490 ppm), while quartz from the Parkin and Hess offsets is enriched in Fe (270–700 ppm) as compared to Ti (44–211 ppm) and Al (95–250 ppm). In contrast to the North Range offsets, quartz from Copper Cliff has low Al concentrations (30–85 ppm) and very low Ti concentrations (<25 ppm). Application of the Ti-in-quartz geothermometer indicates that quartz from the North Range offsets crystallized above 600 °C, while that from the Copper Cliff offset crystallized below 600 °C. The CL responses and trace-element compositions of anhedral quartz from the North Range offsets are consistent with primary crystallization of quartz from magmatic quartz diorite, while those of the granoblastic quartz record dynamic recrystallization and Ostwald ripening. Copper Cliff quartz is anomalous in its CL response, trace-element content, and crystallization temperature, which may reflect overprinting during regional metamorphism of the South Range of the Sudbury Igneous Complex. Quartz CL is demonstrated to be an important tool for discerning and discriminating between paragenetic processes related to the formation of the offset dikes and has clear applications to the study of other quartz-bearing igneous rocks in the Sudbury area.
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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 | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".