The Quaternary Moctezuma volcanic field: A tholeiitic to alkali basaltic episode in the central Sonoran Basin and Range Province, Mexico
Bibliographic record
Abstract
The Quaternary Moctezuma volcanic fi eld at the foothills of the Sierra Madre Occidental, Mexico, is characterized by a close association of tholeiitic and alkaline magmas. The vents of the tholeiitic magmatism (1.7 Ma), which forms the overall mesa morphology of the volcanic fi eld, lie along the major faults that defi ne the eastern margin of the Moctezuma basin. This half-graben formed during the early Miocene as indicated by the emplacement of basaltic fl ows (22.3 Ma), which were intercalated with fanconglomerates of the Baucarit Formation. The youngest volcanics are alkaline lavas (0.53 Ma), which erupted from scoria cones located in the center of the basin. The main mineralogical difference between the Quaternary tholeiitic and alkaline lavas is the composition of the clinopyroxenes: they are Ca-rich in the alkaline lavas, whereas they are subcalcic with orthopyroxene or pigeonite in the tholeiitic lavas. The geochemical data show a gradual change in the characteristics of the lavas. The Sr and Nd isotopic compositions, and the shape of the mid-oceanic-ridge basalt (MORB)-normalized pat- terns, are similar to oceanic island basalt suites, suggesting that the source of the Moct- ezuma volcanic fi eld lavas was dominated by asthenospheric mantle. The absence of mantle or granulite xenoliths in the Moctezuma volcanic fi eld lavas, compared to the neighboring Geronimo volcanic fi eld, refl ects slower ascent rates. The Southern Cordillera Basaltic Andesite (SCORBA)-type geochemical sig- nature of the early Miocene synextensional basalts of Moctezuma compared to the Quaternary Moctezuma volcanic fi eld lavas can be correlated with a progressive thin- ning of the mantle lithosphere during the Neogene.
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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 | 0.000 |
| 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".