Early Palaeozoic oceanic island–seamount assemblage in northern Fujian, South China: Implications for pre‐Devonian tectonic evolution of the Wuyi orogenic belt
Bibliographic record
Abstract
The nature of the Precambrian basement in the Cathaysia Block of South China is controversial, which inhibits our understanding of the pre‐Devonian tectonic evolution of the region. In this study, a suite of amphibolites and marbles in northern Fujian area located in the north of the Cathaysia Block were subjected to LA–ICP–MS U–Pb zircon geochronological and geochemical analyses. Results show that the protolith of the amphibolite formed after ca . 459 Ma, and its metamorphism happened at ca . 429 Ma. The protolith of the marble was deposited after ca . 518 Ma, and its metamorphic age is ca . 437 Ma. The amphibolites are divided into two groups based on geochemical data. Group 1 has an OIB‐like feature that might have formed in an environment characterized by oceanic islands and seamounts. Magmas associated with Group 1 were derived from an enriched mantle source with OIB characteristics. The protolith of Group 2 shows IAB feature that formed in an island arc environment. Marbles are interpreted to represent metamorphosed marine carbonate rocks. Integration of geochronological and geochemical study indicates that the marble and amphibolite should be an early Palaeozoic oceanic island–seamount association. It suggests the Cathaysia Block underwent oceanic subduction during collisional orogenesis in the early Palaeozoic. This subduction is thought to have initiated prior to ca . 437 Ma. The U–Pb zircon ages of younger intrusive granites indicate that final amalgamation occurred before ca . 392 Ma. During this process, east and west Wuyi were amalgamated to form the unified Cathaysia Block. Thus, it suggests that there was no unified pre‐Devonian basement in the Cathaysia Block. The pre‐Devonian tectonic setting of the Cathaysia Block was an accretionary orogeny.
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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 | 0.000 | 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".