Late Triassic granites with mafic microenclaves in the East Kunlun Orogenic Belt, northwestern China: petrogenesis and implications for continental crust evolution and geodynamic evolution
Bibliographic record
Abstract
The magmatic source of the Late Triassic granites in the East Kunlun Orogenic Belt (EKOB) is controversial, which restricts our understanding of crustal evolution and geodynamic evolution in the EKOB. Therefore, this study conducts zircon U‒Pb isotope dating, major and trace geochemical analysis, electron microprobe analysis of feldspar and amphibole, and in situ zircon Hf isotope analysis of Xiangride host granites and their mafic microgranular enclaves (MMEs) in the EKOB to reveal their magmatic source and geodynamic implications. Zircon U‒Pb dating shows that the Xiangride host granites and the MMEs crystallized simultaneously at ca. 228–223 Ma. The MMEs show an igneous texture, finer grain size, higher crystallization temperature and water content, and lower oxygen fugacity than those of the host granite, suggesting that they were probably derived from two distinct primitive magmas. Therefore, the MMEs are considered the products of magma mixing between granitic and mafic magmas. The Xiangride host granites show high Sr/Y (42.0–73.1) and (La/Yb)N (12.7–30.7) ratios, showing affinity with adakites derived from a thickened lower crust. Combined with the indistinguishable εHf(t) values (−3.47 to +0.08) from the coeval mafic rocks, it is concluded that they are derived from partial melting of juvenile thickened lower crust. The adakitic features of the Xiangride host granites and widespread coeval granites indicate the existence of a thickened lower crust before 228 Ma and delamination of the lower lithosphere is likely the geodynamic process resulting in the postcollisional extension regime.
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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".