Multiple metasomatism in Sulu ultrahigh‐P garnet peridotite constrained by petrological and geochemical investigations
Bibliographic record
Abstract
Abstract The pre‐pilot hole (PP1) of the Chinese Continental Scientific Drilling Project (CCSD) recovered drill core samples from a 118 m‐thick section of peridotites located at Zhimafang in the southern Sulu UHP terrane, China. The peridotites consist of phlogopite‐bearing garnet lherzolite, harzburgite, wehrlite and dunite. Some peridotite layers contain magnesite and Ti‐clinohumite, and are characterized by LREE and LILE enrichment and HFSE depletion. Phlogopite (Phl) occurs in the peridotite matrix and is LILE‐enriched with low Zr/Hf ratios (0.19–0.60). Phlogopite shows a mantle signature in H and O isotopes (δ18O: +5.4‰ to +5.9‰, and δD: −76‰ to −91‰). Ti‐clinohumite (Ti‐Chu) is Nb and Ta‐enriched and has higher Ti and HREE concentrations than phlogopite. Magnesite (Mgs) occurs as megacrysts, as a matrix phase, and as veins (±Phl ± Ti‐Chu), and contains low REEtotal contents (<0.3 ppm) with a flat REE pattern. The δ18O values (+5.5‰ to +8.0‰) of magnesite are in the range of primary carbonatite, but the δ13C values (−2.4‰ to −3.4‰) are slightly more positive than those of the mantle and of primary carbonatite. Petrochemical data indicate that the Zhimafang peridotite was subjected to three episodes of metasomatism, listed in succession from oldest to youngest: (1) crystallization of phlogopite in the mantle caused by infiltration of K‐rich hydrous fluid/melt; (2) formation of Mgs and Mgs ± Phl ± Ti‐Chu veins possibly caused by infiltration of mantle‐derived carbonatitic melt with a hydrous silicate component; and (3) replacement of magnesite, garnet and diopside by dolomite and secondary hydrous phases caused by a crust‐related, CO2‐bearing, aqueous fluid. Stable isotopic compositions of phlogopite and magnesite indicate metasomatic agents for events (1) and (2) are from an enriched mantle. Multiple metasomatism imposed on mantle peridotite of variable composition led to significant compositional heterogeneity at all scales within the Zhimafang peridotite.
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 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".