The geochemistry of the volcanic rocks of Canouan, Grenadine islands, Lesser Antilles arc
Bibliographic record
Abstract
Abstract In late Oligocene or early Miocene, a series of basalts and basaltic andesites erupted on the island of Canouan and formed the Old Volcanic Massif (OVM). In a second eruptive phase a series of basalts, basaltic andesites and andesites formed the upper part of the Canouan Formation (CF; lower Middle Miocene; post‐16 Ma) and the Upper Volcanic System (UVS; end‐Miocene; 6.8 Ma). These two eruptive phases are characterized by systematic differences in isotope ratios and chemical composition. The OVM rocks have 87Sr/86Sr and 143Nd/144Nd ratios ranging from 0.70512 to 0.70657 and 0.512415 to 0.512414, whereas in the CF/UVS rocks the ratios range from 0.70454 to 0.70493 and 0.512924 to 0.512843. In addition, the rocks of OVM also have lower ΣFe2O3 and Co contents, and higher La/Yb ratios than those of the CF/UVS. The isotopic and chemical data suggest that both suites were formed from similar partial melts of a subduction‐modified, depleted spinel‐lherzolite source. These data also show that the OVM melts assimilated relatively large amounts of highly radiogenic crustal material, whereas the CF/UVS melts assimilated relatively small amounts of highly radiogenic crustal material. The chemical and isotopic variations of the OVM rocks are consistent with the removal of mixtures of clinopyroxene, plagioclase and magnetite during assimilation‐fractional‐crystallization. Within the CF/UVS, the chemical and isotopic variations can be explained in terms of minor crustal assimilation; the removal of olivine, clinopyroxene, plagioclase and magnetite to form the basalts and basaltic andesites; and the removal of clinopyroxene, plagioclase, magnetite and amphibole to form the andesites. Copyright © 2008 John Wiley & Sons, Ltd.
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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 | 0.003 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 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".