Petrogenesis of Silurian Granitoids in the Western Segment of the North Qilian Accretionary Belt, China: Insights Into the Closure of the Northernmost Branch of the Proto‐Tethys Ocean
Bibliographic record
Abstract
ABSTRACT The North Qilian Accretionary Belt, situated at the northernmost extent of the Proto‐Tethys tectonic domain, preserves key tectonic events such as Proto‐Tethys Ocean subduction and accretion. Despite ongoing debates about the closure mechanisms and timing of the North Qilian Ocean, our study presents novel findings on granitoids from the Changma region in the western segment of the North Qilian Accretionary Belt. Zircon U–Pb dating indicates an emplacement age of 436 Ma for the Qingshixia pluton and 425 Ma for the Heixialao pluton. The ε Hf (t) values of the Qingshixia granodiorite range from +8.25 to +10.89, with TDM2 model ages estimated between 614 and 716 Ma. In contrast, the ε Hf (t) values of the Heixialao monzogranite range from +1.79 to +4.48, with TDM2 model ages spanning from 1127 to 1291 Ma. The Qingshixia granodiorite displays adakitic traits, characterised by high Sr, low Y, low Yb, and a low K2O/Na2O ratio, whilst the Heixialao monzogranite exhibits peraluminous, high‐potassium calc‐alkaline features. The low concentrations of Ni and Cr, along with moderate Mg# values, suggest that the Qingshixia granodiorite likely originated from the partial melting of a subducting slab. By comparison with experimental melts, the relatively low Rb/Ba and Rb/Sr ratios and higher zircon saturation temperatures of Heixialao monzogranite suggest that it may have formed from partial melting of the mafic middle and lower crust. Integrating these findings with regional geological features and differences between east and west segments, we propose that the western segment of the North Qilian Ocean basin may have closed during the Late Silurian, contributing to a diachronic closure process from east to west and offering insights into the tectonic evolution of the Proto‐Tethys Ocean.
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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 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".