The Pelona-Pico Duarte basalts Formation, Central Hispaniola: an on-land section of Late Cretaceous volcanism related to the Caribbean large igneous province
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Bibliographic record
Abstract
Located in Central Hispaniola, the Pelona-Pico Duarte basalts Formation (Fm.) offers an opportunity to study the Late Cretaceous Caribbean large igneous province magmatism on land. It is composed by a ~2.5km-thick pile of massive and monotonous submarine flows of basalts, locally intruded by synvolcanic dikes and sills of dolerite. The Pelona-Pico Duarte basalts Fm. was emplaced onto Turonian-Lower Campanian island-arc volcanic and sedimentary sequences, and is overlain by Maastrichtian platformal carbonates. Two 40Ar/39Ar plateau ages indicate both extrusive and intrusive magmatic activity at least during the 79-68Ma interval (Middle Campanian to Maastrichtian), so the magmas were in part coeval with the late phases of the Caribbean large igneous province. The basalts have a restricted major-and trace-element, and isotopic, compositional variation. For a range of 47.6- 50.2wt.% SiO2, the Pelona-Pico Duarte basalts Fm. has relatively high contents in TiO2 (1.5-3.6wt.%) and Fe2O3T (10.7-13.1wt.%). On the basis of MgO contents, samples can be classified into tholeiitic basalts (lt;8wt.%) and high-Mg basalts (8-12wt.%). Mineral assemblages and major element compositional trends indicate that basalts derived from tholeiitic parental magmas by fractionation of olivine plus spinel, clinopyroxene and orthopyroxene, observed as microphenocrysts, as well as plagioclase and Fe-Ti oxides. In a MORB-normalized multi-element plot, the basalts have light rare earth elements (LREE) enriched ([La/Nd]N=1.5-2.2) and heavy rare earth elements (HREE) depleted ([Sm/Yb]N=2.1-3.7) patterns, with very high Nb contents (11-30ppm). These patterns and the values of trace element ratios (K/Balt;20, Ti/Vgt;20 and Zr/Nblt;10) are characteristic of transitional and alkalic oceanic-island basalts. In terms of Sr-Nd isotopic composition, the samples are homogeneous and enriched relative to older Caribbean large igneous province units in Hispaniola, with (87Sr/86Sr)i ratios between 0.70330 and 0.70348 for a very restricted range of (eNd)i values between +5.0 and +5.9 (where i=70Ma). The Pelona-Pico Duarte basalts Fm. are interpreted as partial melts of a plume-related, deep enriched source, which have not been contaminated by active subduction. Mantle melt modelling indicates that both high-Mg basalts and basalts formed by mixed melts of both garnet and spinel lherzolite in variable amounts. Melts incorporated at different mantle depths, most probably in relation to the melt column processes in an upwelling plume. The Pelona-Pico Duarte basalts Fm. has significantly different values of petrogenetic tracers compared to underlying arc-related lavas, indicating a fundamental change in the mantle sources. It has geochemical affinities with the mantle domain influenced by the Late Cretaceous Caribbean plume, suggesting that enriched mantle was flowing toward the NE, to the mantle wedge region of the Caribbean island-arc, in response to rollback of the SWdirected subduction of the proto-Caribbean slab
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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 | 0.001 | 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 | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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 it