Every intrusion has its time: New zircon U-Pb ages from the Greater Antilles Arc in the Cordillera Central, Dominican Republic
Bibliographic record
Abstract
The Cordillera Central on the island of Hispaniola comprises a section through the crust of the Late Cretaceous phase of the Greater Antilles Arc. The gabbroic-tonalitic batholiths of the Cordillera Central are widely considered to represent the temporal main axis of this island arc. Although they have been studied extensively, the timing of batholith emplacement is not well constrained. We present new LA-ICP-MS U-Pb zircon ages and whole-rock geochemical data from diorites, tonalites, and granites of the El Río, El Bao, Jumunuco, and Loma de Cabrera batholiths, and from tonalite boulders deposited in the Eocene-Oligocene Velázquitos Formation. The sample ages range from 97 to 80 Ma with small differences between the intrusive bodies. Samples from the El Río, Jumunuco, and Loma de Cabrera batholiths cover most of the above age range, while the rocks of the El Bao pluton yield a well-defined maximum around 87 Ma. In the El Río batholith, U-Pb ages are in good agreement with the exposed contact relationships. Based on their composition and existing geochronological data, we divide the intrusive history of the Cordillera Central into four stages reflecting different magma compositions: ultramafic to dioritic magmatism lasted from 105 to 87 Ma, tonalite units formed between 96 and 84 Ma, felsic tonalites and granites intruded from 87 to 80 Ma overlapping with a younger phase of dioritic magmatism between 84 and 78 Ma. The geochemical signatures of the felsic tonalites of the Jumunuco batholith and the granites of the El Río batholith are similar to the rhyolitic and dacitic island-arc volcanics from the Restauración Formation of the Tireo Group, thus confirming the relationship between the volcanic and plutonic units of the Greater Antilles Arc. Based on petrographical, geochemical, and geochronological data of the tonalite samples from the Velázquitos Formation, we interpret these boulders as being eroded from the Jumunuco batholith or the related Buena Vista pluton. • New Zircon U-Pb ages of plutonic rocks in the Dominican Cordillera Central. • Crystallization ages range between 80 and 97 Ma. • Batholith emplacement occurred in four compositionally different phases. • Complex contact relationships in the El Río batholtih confirmed by zircon ages. • Geochemical data confirm relationship to island-arc rhyolites and dacites.
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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) | 0.000 | 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) | 0.030 | 0.001 |
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 teacher head, 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".