Permian tectonic evolution of the southwestern Ordos Basin, North China: Integrating constraints from sandstone petrology and detrital zircon geochronology
Why this work is in the frame
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Bibliographic record
Abstract
The Late Palaeozoic dynamic setting of the Ordos Basin in the southwestern North China Craton (SW‐NCC) is poorly constrained due to limited understanding on the source‐to‐sink relation. This study presents integrated provenance clues from the Permian strata in the southwestern Ordos Basin to trace the sources and to discuss the tectonic setting of the basin in the SW‐NCC. The reconstructed palaeocurrent directions of these Permian sediments generally point to the northeast and suggest the dominant sedimentary influx from the southwest. Modal composition analysis shows the Permian deposits have an overwhelming derivation from mixed sources containing orogeny, continental block, and magmatic arc. Zircons from the lower section yield major age clusters of ~300–270 Ma and ~2,500–1,700 Ma. While, zircon age spectra for the upper section are marked by the abundance of ~1,000–800 Ma and ~500–400 Ma ages, and the lack of Permian populations. Sources of the lower section were interpreted to be the arc terrane along the southern border of SW‐NCC, in contrast, sources of the upper part were attributed to the Central Qilian Block. Zircons of ~300–270 Ma indicate significant magmatic activities in a rapidly uplifting continental arc, yielding an additional clue for the subduction and the existence of the Mianlue Ocean in the northeastern Palaeo‐Tethys. The changes in provenance and depositional rate at the Middle Permian indicate the rapid subsidence along with the intensive uplift of the continental basement in the SW‐NCC. These signatures likely infer that the back‐arc basin may have evolved into a compressional setting at that time.
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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 | 0.001 |
| 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 it