Thickening and partial melting of the Northern Qinling Orogen, China: insights from zircon U–Pb geochronology and Hf isotopic composition of migmatites
Bibliographic record
Abstract
The widespread migmatites in the Precambrian basement of the North Qinling Belt are products of partial melting of the Earth's crust and record the tectono-thermal response to Late Paleozoic collision along the Shangdan suture. The morphology and trace element geochemistry of zircons from the migmatites suggest a metamorphic origin related to partial melting. The zircons from leucosome, melanosome and banded migmatites yield U–Pb weighted mean ages of 408 ± 2, 403 ± 2 and 400 ± 2 Ma, respectively, constraining the timing of migmatization. The granitic dyke intruded into the migmatites gives a zircon U–Pb weighted mean age of 396 ± 2 Ma, constraining the minimum time of migmatization. Zircons from the melanosome and banded migmatite yield upper intercept ages of 1088–1061 Ma, representing the protolith ages of the basement of the North Qinling Belt. The zircon rims of the melanosome and banded migmatite predominantly display negative and positive ε Hf ( t ) values, respectively, suggesting the variable input of mantle material. Together with the regional geology and previous geochronological data, we propose that the thickening and partial melting in the North Qinling Belt was induced by the collision along the Shangdan suture between the North and South China Blocks from c. 408 to 400 Ma. Supplementary material: LA-ICP-MS U–Pb data, Lu–Hf isotopic compositions and trace element geochemistry data of the zircons and Ti-in-zircon thermometry are available at https://doi.org/10.6084/m9.figshare.c.4521389
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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 | 0.000 | 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) | 0.000 | 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".