Zircon U–Pb ages and Hf isotope compositions of the Chencai migmatite, central Zhejiang Province, South China: constraints on the early Palaeozoic orogeny
Bibliographic record
Abstract
Abstract U–Pb ages and Hf isotope compositions of zircons from the Chencai complex in Zhejiang Province have been determined to provide constraints on mechanisms of migmatization and tectonic evolution related to the early Palaeozoic orogeny in the Cathaysia Block, South China. Zircons from leucosome samples of migmatites are characterized by nebulous overgrowths enclosing inherited cores or occur as newly formed grains with weak zoning. Five samples gave weighted mean ages ranging from 438±3 Ma to 432±4 Ma, which are interpreted as recording the time of anatexis of a regional tectono-thermal event. Their ε Hf ( t ) values range from −21.4 to −4.8 (with peak at −11), with corresponding T DM2 ages of 1.73–2.77 Ga (with peak at c. 1.9–2.3 Ga), suggesting that the protoliths formed by reworking of ancient crust evolved from Late Palaeoproterozoic – early Archaean crust–mantle differentiation. The migmatization was spatially and temporally associated with reported 460–435 Ma metamorphism with a clockwise pressure–temperature ( P – T ) path and was most likely controlled by crustal thickening driven by the early Palaeozoic orogenesis. The T DM2 ages of the Chencai complex are consistent with those of the Wuyi–Yunkai structural belt in the Cathaysia Block, but distinct from those (with peak at 2.7–3.0 Ga) of the Badu complex which lacks early Palaeozoic tectono-thermal records. The data support the suggestion that a postulated geological entity, instead of the east domain (the Badu complex being its main part) of the Cathaysia Block, was probably involved in the early Palaeozoic orogeny.
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How this classification was reachedexpand
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 | 0.000 | 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 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.008 | 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 teacher head, 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".