Late Mesozoic ductile deformation and exhumation along the Shangdan suture zone in the Qinling Orogenic Belt, China
Bibliographic record
Abstract
The Qinling Orogenic Belt (QOB) is a multi‐stage orogenic belt recording subduction and collision processes. The ductile shearing deformation with different properties and ages is developed on the boundary of the different litho‐tectonic units, which can be used to decipher the tectonic evolution of the QOB. Previous studies mainly concentrated on the pre‐Late Mesozoic shearing deformation, while the Late Mesozoic shearing deformation received less attention. It restricts the understanding of the Late Mesozoic tectonic evolution of the QOB. Hence, we conducted detailed field structural analysis and laboratory analysis of the Shagou shear zone (SGSZ) in the middle part of the Shangdan suture zone (SDSZ). The SGSZ, developed in the southern margin of the Baliping pluton, is an S–SSW‐dipping sinistral strike‐slip ductile shear zone with a top‐to‐the‐ESE shear sense. The mylonite protoliths are voluminous Late Triassic granites (200–215 Ma) and a small amount of Neoproterozoic granites (759 Ma) and Early Cretaceous granites (145 Ma). Microstructures and geothermobarometer results suggest that the ductile shearing deformation occurred under high greenschist–low amphibolite‐facies conditions (400–650°C) at middle crustal depths (13–21 km). Zircon U–Pb and amphibole‐biotite 40Ar/39Ar dating results constrain the timing of shearing deformation to 135–145 Ma and the rapid exhumation of the SGSZ to 115–135 Ma. Combining with the regional data, we consider that the sinistral strike‐slip shearing deformation in the SGSZ controls and accommodates the south‐eastward extrusion of the East SQB under the intracontinental compression. Subsequently, the intracontinental extension led to the rapid exhumation of the SGSZ.
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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 | 0.001 |
| 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".