Spherulitic Aphyric Pillow-Lobe Metatholeiitic Dacite Lava of the Timmins Area, Ontario, Canada: A New Archean Facies Formed from Superheated Melts
Bibliographic record
Abstract
Fragmental rocks of the V10 units of the Vipond Formation of the Tisdale assemblage previously have been identified as pillow basalts, but many samples are shown to be intermediate-to-felsic in character, likely tholeiitic dacite in composition. Specifically, the V10b unit is mapped as a pillow-lobe dacite. Aside from being more geochemically evolved in terms of their “immobile” trace elements, these rocks differ from typical pillow basalts in that they have more abundant primary breccia and hyaloclastite. The pillow lobes are contorted, having been folded in a plastic state and are zoned, typically having a spherulite-rich core. Moreover, the flows are aphyric, interpreted to mean that they were erupted in a superheated state. This along with their pillow-lobe nature demonstrates that they were erupted as relatively low-viscosity melts for such silicic compositions. Interaction with water quenched the outer pillow lobe and contributed to the formation of the abundant breccia. The fact that the melt was crystal and microlite free inhibited crystal growth, such that the bulk of the lobes were quenched to crystal-free glass. Nucleation occurred only in the cores, where cooling rates were lower in comparison to the medial and exterior areas of the pillow lobes, although in the cores crystal growth rates were high so that abundant spherulite formation took place. The flows are exposed over a strike length of more than 10 km and are interpreted to be continuous and to have resulted from fissure eruptions. The resulting porous, permeable, high Fe/Mg, high-surface area glassy rocks may have been ideal for channeling and reacting with gold-bearing hydrothermal solutions. Descriptions of most other Archean subaqueous felsic lobes document that the lavas were phyric and that spherulites formed near the external lobe margin. The distinctly different zoning of the V10b pillow lobes suggests that they constitute a new Archean facies formed from superheated melts.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 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) | 0.036 | 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 teacher head, 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".