Geochronology and geochemistry of the Yazidaban ophiolitic mélange in Qimantagh: constraints on the Early Paleozoic back-arc basin of the East Kunlun Orogen, northern Tibetan Plateau
Bibliographic record
Abstract
The East Kunlun Orogenic Belt of the northern Tibetan Plateau can be divided by the Qimantagh–Xiangride, Aqikekulehu–Kunzhong and Muztagh–Buqingshan sutures into, from north to south, the Northern Qimantagh, Central Kunlun and Southern Kunlun belts. The Yazidaban ophiolitic mélange, located in the westernmost region of the Qimantagh–Xiangride suture between the Northern Qimantagh and Central Kunlun belts, consists predominantly of serpentinite, basalt, diabase and andesite. The serpentinites are characterized by low total rare earth element (ΣREE) concentrations and depletion of mid-REEs, showing an ophiolitic ultramafic affinity. The basalts have low ΣREE concentrations, a slight enrichment in light REEs, depletion of large ion lithophile elements and insignificant fractionation of high field strength elements, which are attributed to an incompatible element-enriched mid-ocean ridge basalt. Both diabases and andesites are characterized by high ΣREE, strong enrichment in light REEs, depletion of Nb, Ta, P and Ti, and significant fractionation of high field strength elements. These geochemical characteristics indicate that the diabase and andesite were mostly generated in a subduction-related setting. Igneous zircons from the diabase yielded a 206 Pb/ 238 U age of 421.5 ± 2.2 Ma (MSWD = 0.44), representing the formation time of the subduction-related rocks. Together with the regional geology, these constraints on the ultramafic rock, basalt, andesite and diabase suggest that the Yazidaban ophiolitic mélange represents the remnants of oceanic crust from a back-arc basin and the associated subduction-related magmatic rocks. Supplementary material: Details of U–Th–Pb laser ablation inductively coupled plasma mass spectrometry data of zircons from the diabase, and major and trace element compositions for the samples from the Qimantagh mélange, East Kunlun Orogen are available at https://doi.org/10.6084/m9.figshare.c.4283219
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.003 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".