Mélanges in southern Mexico: geochemistry and metamorphism of Las Ollas complex (Guerrero terrane)
Bibliographic record
Abstract
Las Ollas complex (LOC) is a subduction complex spatially associated with the early Cretaceous Zihuatanejo-Huetamo subterrane (Guerrero terrane) in southern Mexico. LOC tectonic mélanges compose of a stack of east-dipping, west-vergent tectonic sheets containing blocks of metabasalt, metadolerite, metagabbro, ultramafics, volcaniclastics, quartz-rich sandstone, and chert enveloped in a highly sheared clastic or serpentinitic matrix. Most igneous and igneous-derived metamorphic blocks show geochemical and isotopic features typical of island-arc tholeiitic suites: (i) low TiO2 (0.13 to 0.91%) and Zr (5 to 57 ppm) contents; (ii) high (LFSE/HFSE)N ratios; low LaN/YbN (0.5 to 4) values; and, high εNd(T) (+7.9 to +8.0) ratios. Petrographical and mineral chemistry evidence indicates that blocks underwent early recrystallization under high pressure and low temperature (HP-LT), blueschist facies conditions during subduction. Typical assemblages include blue (sodic through calco-sodic to Na-rich calcic) amphibole + lawsonite ± tremolite ± Mg-chlorite ± white mica ± albite ± quartz. Phase relations and chlorite thermometry suggest temperatures of about 200°-330o C and pressures of 5-7 kbar. It is proposed that sedimentary blocks were generated by in situ remobilization and mixing, whereas igneous blocks most probably derived from the chemically and isotopically identical Zihuatanejo island-arc suite. Our data suggest that LOC represents part of a subduction complex formed by eastward-directed subduction related with the evolution of the early Cretaceous Zihuatanejo island arc.
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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 | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 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".