Chemical variation in Al<sub>2</sub>O<sub>3</sub>CaONa<sub>2</sub>OK<sub>2</sub>O space: controls on the peraluminosity of the South Mountain Batholith
Bibliographic record
Abstract
The South Mountain Batholith (SMB) of southwestern Nova Scotia is a large, highly differentiated, peraluminous, granitic batholith in which the average A/CNK (mol Al 2 O 3 /mol(CaO + Na 2 O + K 2 O)) increases from 1.16 to 1.23 with chemical evolution. We use vector analysis of variations solely in Al 2 O 3 (CaO + Na 2 O + K 2 O) space to assess the fractionation, assimilation, fluid, and source controls on the peraluminosity of the SMB. With increasing chemical evolution, Al 2 O 3 decreases, CaO decreases sharply, Na 2 O is approximately constant, and K 2 O increases in the early and middle stages but decreases in the most evolved stage. Initial 87 Sr/ 86 Sr and 143 Nd/ 144 Nd isotopic ratios for granites and average Meguma Supergroup country rocks suggest an upper limit of ~33% of wall-rock contamination for the most evolved rocks, if the most primitive rocks are uncontaminated. The trend of chemical evolution of the SMB through Al 2 O 3 (CaO + Na 2 O + K 2 O) space is the resultant of all input vectors (processes). In the early stages, those processes are fractional crystallization of plagioclase ± K-feldspar ± cordierite ± biotite and contamination by country rocks. In the later stages, those processes are fractionation of plagioclase ± K-feldspar ± andalusite ± muscovite, further contamination by country rocks, and selective partitioning of CaNaK into aqueous fluid phases. Clear geochemical evidence for variation in the source composition is lacking.
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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 | 0.000 | 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) | 0.001 | 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".