A new look at the geodynamic development of the Ediacaran–early Cambrian forearc basalts of the Tannuola-Khamsara Island Arc (Central Asia, Russia): Conclusions from geological, geochemical, and Nd-isotope data
Bibliographic record
Abstract
Abstract Oceanic igneous rocks throughout the Altai-Sayan Fold Belt (ASFB) in central-southern Siberia are often considered to be late Precambrian–early Paleozoic accreted elements of oceanic crust – often of uncertain paleogeographic or geodynamic origin. We explore the role of suprasubduction zone settings in the formation of different ASFB terranes. Our study offers a non-accretionary perspective on the tectonomagmatic development of basalt-bearing units in the ASFB on the example of the forearc terrane of the Ediacaran–early Cambrian Tannuola-Khamsara island arc (herein termed Sayan-Tuvan forearc zone). We describe the geochemistry, structural geology, and stratigraphic relations of basalts of the Aldynbulak, Uttug-Khaia, and Chingin formations, which are integral parts of the Sayan-Tuvan forearc zone. The Aldynbulak basalt samples mainly fall in the compositional fields of ocean island basalts and enriched mid-ocean ridge basalts (E-MORB) and likely derived from a deep mantle source. The Uttug-Khaia and Chingin basalts are N- and E + T-MORB-like basalts, carrying forearc geochemical signatures. Specifically, the Chingin Formation contains boninite dikes and is associated with a boninite-bearing ophiolite. Boninites are commonly associated with forearc magmatism and thus a forearc formation setting is likely. Tectonic and stratigraphic considerations imply that the Aldynbulak basalts formed first, followed by the Uttug-Khaia and later the Chingin basalts and boninites. A schematic model, involving decompression melting of the mantle, is proposed for the development of the studied forearc basalt suites that are linked with the growth of the Tannuola-Khamsara island arc system 580–540 million years ago.
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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 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.004 | 0.002 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 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".