New detrital zircon U-Pb ages from BIF-related metasediments in the Ntem Complex (Congo craton) of southern Cameroon, West Africa
Bibliographic record
Abstract
Banded Iron Formations (BIFs) were formed by contemporaneous events of active sediments supply and the venting of a hydrothermal fluid source at the Mid-Ocean-Ridge. BIFs within the Ntem Complex at the northern edge of the Congo Craton are intercalated with metasandstones and siltstones. SHRIMP U-Pb analysis on detrital zircons obtained from these metasediments gave variable ages from over 3000 Ma to 1000 Ma with the maximum age of deposition clustered around 1200 Ma and the peak of deposition at 1800 Ma. This age range suggested that the sub-basin was opened sometime in the Archean and remained active up till the Neoproterozoic. Zircons with Archean ages have a provenance linked to the charnockitic suite and the high-K granites within the Ntem Complex. The Paleoproterozoic ages are attributed to clastic inputs from the neigbouring Nyong Series west of the Ntem Complex. Also the peak of deposition in the Proterozoic could probably be explained by the globally recognized intense crust-forming processes in the Early Proterozoic time. The provenance of the younger Neoproterozoic ages is tied to various lithologies within the northern mobile belts of the Adamawa-Yade massifs and correlates with Neoproterozoic sedimentation ages in the Yaoundé, Lom and Poli series. The Neoproterozoic ages obtained are comparable to those obtained from metasediments of the Amazonian Craton and provide evidence of Pre-Gondwana assemblage of the Congo and the S?o Francisco Cratons.
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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 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".