Subduction and melting of biogenic and ferromanganese sediments as evidenced by sub-Moho granitoids
Bibliographic record
Abstract
Mantle-hosted granitoids (MHG) from the supra-subduction Samail ophiolite in Oman and the United Arab Emirates exhibit diverse compositions, highlighting variations in petrogenesis and source contributions. Previous isotopic data indicate these MHG originated through the interaction of sediment-derived with basaltic melts from an underthrust oceanic plate within the mantle wedge. The sedimentary contribution was attributed to the partial melting of pelitic to siliceous (bio-siliceous) material atop the subducted plate based on elevated zircon δ 18 O values (∼14–28 ‰). To further evaluate this hypothesis on Samail MHG petrogenesis and source contribution, we present new and compiled radiogenic (Sr-Nd-Hf-Pb) and stable (O-Li-H) isotopes, along with zircon trace element analyses. The variable Sr and Pb isotopic signature support a mixed origin involving altered mafic and sedimentary sources in the formation of the MHG. Negative whole-rock εNd, coupled with elevated δ 7 Li in muscovite suggest the involvement of sedimentary sources and particularly those resembling deep-sea ferromanganese-rich sediments. We propose a new model identifying ferromanganese sediments as a potential source given their widespread distribution across the ocean floor, broad range of δ 18 O (up to 29.5 ‰), slightly positive Hf values, seawater-like δ 7 Li signatures (median of ∼27 ‰), and zircon trace element compositions lacking a signature of monazite co-precipitation, which match the signatures required for the genesis of the Samail MHG. Preservation of oceanic lithosphere in the geological record is limited, and MHG in ophiolites are uncommon. Therefore, the Samail MHG are key examples of crustal materials transported to the mantle, with implications for mantle heterogeneity and arc mantle redox budget. • Isotopes of Samail mantle-hosted granitoids reflect sediment-basalt interaction • Isotopes and trace elements suggest Fe-Mn sediments as a source for mantle-hosted granitoids. • These granitoids serve as key examples of crustal materials recycled into the mantle.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| 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".