Linkages between the southern Patagonia Pre-Permian basements: new insights from detrital zircons U
Bibliographic record
Abstract
The Patagonian basement rocks are dominated by Precambrian to Early Paleozoic metamorphic rocks intruded by Paleozoic granitoids.Recently discovered basement rocks in the Cerro Negro District are characterized mainly by quartz-muscovite-chlorite schists; the metamorphic grade reaches greenschist facies (biotite-garnet grade) with a regional S 1 schistosity subparallel to the original sedimentary structure S 0 and a secondary nonpenetrative S 2 foliation.New detrital zircon U-Pb geochronology shows that maximum depositional ages for detrital zircons are Devonian, ages of 379 ± 4Ma.These results suggest that the Cerro Negro basement rocks are the youngest basement in the Deseado Massif, overlapping some detrital zircon ages in the eastern Andean Metamorphic Complex in the Andean region.Most of detrital zircons are igneous in origin with a major peak around ~396Ma, probably sourced from the Devonian granitoids of the Río Deseado Complex (El Laurel and Bahía Laura granites) and equivalent northern Patagonia granitoids (e.g.Colan Conhué and Lago Lolog granites).Secondary peaks correspond to Ordovician to Silurian ages, being the Río Deseado Complex and La Modesta Formation (and their igneous contributors) the possible sources of the zircons.The minor oldest peaks yield Cambrian-Neoproterozoic; Mesoproterozoic and Paleoproterozoic-Archean ages, evidencing a common source from the interior of Gondwana.The results provide new insights about the relationships between the pre-Permian metasedimentary rocks of the extra-Andean and Andean region during Mid-Paleozoic ages.Patagonia.Deseado Massif.Basement.U-Pb SHRIMP.Cerro Negro.
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| 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 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".