Metamorphic petrology of calc-silicate nodules from chlorite to sillimanite grade, Liverpool-Pubnico area, Nova Scotia
Bibliographic record
Abstract
Calc-silicate nodules occur within the low-pressure regionally metamorphosed rocks of the Meguma Group in southwestern Nova Scotia. Mineral zonation occurred within the nodules during metamorphism, resulting in complex patterns of mineral assemblages with increasing grade. Petrological, petrographic and electron microprobe studies demonstrated T-P conditions that ranged from 400 to 600°C and 2.5 to 4.0 kbar. To evaluate the extent of Ca and Si metasomatic exchange between the surrounding siliceous rocks and calcareous nodules during metamorphism, the mineral assemblages of the nodules were analyzed and compared from 40 samples from chlorite to sillimanite grades, collected between Pubnico and Liverpool. Calc-silicate nodules show distinct zonation, with increasingly calcareous minerals towards the cores of the nodules. Lack of zoning at the lowest grade (Green Bay) shows that mineral zonation within the nodules is not a result of diagenetic processes but rather of grade-controlled reactions. At chlorite grade there was little exchange of Ca and Si ions between the country rock and nodules. Ca metasomatism appears to have been restricted to the nodules within medium-grade nodules whereas at sillimanite grade, there was likely an exchange between the nodules and country rock. Zonation patterns within nodules at the same grade are not systematic and are probably controlled by several factors: metamorphic grade and lithology of the host rock and nodule. T-X calculations for nodule core assemblages show that the fluids involved during metamorphism of the nodules were generally water-rich, presumably from the breakdown of hydrous minerals. At higher grades Xco₂ may have varied due to higher CO₂ producing reactions, but is complicated by retrograde effects possibly associated with veining and scheelite mineralization.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.011 | 0.003 |
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; both teacher heads agree on what is shown here.
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".