Plutonic record of a caldera-forming silicic eruption: The shatter zone of the Cadillac Mountain granite, coastal Maine
Bibliographic record
Abstract
Abstract Although it is widely accepted that large silicic calderas are associated with voluminous synvolcanic intrusive complexes at depth, geological evidence for caldera-forming eruptions preserved in plutonic rocks has largely been elusive. Here, we document a rare example of such evidence in the Cadillac Mountain intrusive complex, Maine (USA), where erosion has revealed a remarkable marginal “shatter zone” that records evidence for a major caldera-forming eruption. This shatter zone, up to >1 km wide, is bounded by a steep ring fault at its outer margin, which grades inward into Cadillac Mountain granite. Its outer margins are characterized by intensely brecciated and deformed country rock injected by felsite veins, reflecting explosive fragmentation associated with eruptive decompression. This marginal facies grades inward to a chaotic mélange of variably rounded and remelted country rock blocks in granitic matrix, reflecting debris eroded from ring fault conduit walls and milled in an eruptive jet before collapsing onto crystal mush. Further inward, blocks up to 80 m in size were stoped from the collapsing chamber roof and settled onto strong mush. Textural and chemical variations in the shatter zone matrix reveal syneruptive ascent of distinct silicic and more mafic magma from depth, which was likely drawn through the highly permeable shatter zone toward areas of low pressure beneath active vents. The Cadillac Mountain shatter zone provides clear evidence for a major eruption preserved in the plutonic record and supports the origin of some granites as the cumulate roots of large silicic volcanic systems.
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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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".