The clastic record of an early Brasiliano Orogeny: pre-collisional subduction-related metamorphism within the southern Borborema Province through detrital rutile analysis
Bibliographic record
Abstract
The ubiquity of detrital zircon in clastic sediments made zircon one of the primary minerals for provenance and tectonomagmatic studies. However, its high U–Pb closure temperature (>900°C), limited growth of new zircon under upper amphibolite–eclogite facies, inherited bias towards felsic sources and refractory behaviour rarely representing first-cycle sedimentation can hamper the detection of key tectonomagmatic events. Other mineral assemblages, such as rutile, which formed in medium- to high-grade metapelite and metabasite during high-pressure and low-temperature subduction metamorphism can help to provide a complete record of polyphase orogenic evolution. In this study, we present U–Pb ages and trace elements in detrital rutile from the Ordovician Tacaratu Formation (Tucano–Jatobá Basin) to track the complete polyphase evolution of southern Borborema Province. Coupled U–Pb detrital zircon and rutile analysis revealed that detrital zircon ages lag detrital rutile ages by c. 100 myr. Three rutile age peaks at c. 767, 669 and 595 Ma were recognized, agreeing with subduction in magma-poor orogenic phases (lulls) between relatively high magma generation phases (flare-ups). The detrital rutile ages record earlier phases of Brasiliano Orogeny in southern Borborema Province (subduction-related metamorphism; closure of Sergipano Ocean), as this orogeny culminated in the collision of blocks followed by high-temperature metamorphism.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.000 | 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) | 0.001 | 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".