Detrital Platinum-Group Minerals and Gold In Placers of Southeastern Samar Island, Philippines
Bibliographic record
Abstract
Abstract The present work provides a comprehensive description of the assemblage of detrital platinum-group minerals (PGM) and gold found in the Llorente river and its tributaries draining the area west of the town of Llorente in southeastern Samar, Philippines. Altogether, 610 grains of detrital PGM were studied by reflected light and scanning electron microscopy, and 464 quantitative electron-microprobe compositions were obtained from 265 grains of PGM in polished sections. The concentrates are dominated by grains of gold, followed by accessory PGM grains. The assemblage of detrital PGM is composed of mainly monophase grains of Os-Ir-Ru-(Pt) alloys (41.3%), Pt-Fe alloys and platinum (together 40.5%), laurite–erlichmanite (16.6%), and rare other PGM (1.6%). Grain sizes of the PGM range from ∼50 μm up to 2–3 mm; median sizes are 250 μm for Pt-Fe and Os-Ir-Ru alloy grains, and 420 μm for laurite–erlichmanite grains. Gold grains are commonly silver-rich and display leached outer zones of Ag-poor gold. Grain sizes range from ∼50 μm to 6.8 mm (median about 400–500 μm). Notable is the presence of rare tetraauricupride. Both the regional bedrock geology and the distinct PGM assemblage indicate that the PGM originated from Alpine-type ophiolite rocks, probably chromitites, which are common in the study area drained by the Llorente river and its tributaries in the Eastern Bicol-Eastern Mindanao ophiolite belt of Samar. Gold and tetraauricupride may originate from diverse sources. Rare inclusions of tellurides and chalcopyrite in detrital gold grains suggest epithermal gold vein deposits or gold-bearing porphyry copper mineralization as sources of the gold, whereas the tetraauricupride grains may originate from hydrothermal mineralization, different from the gold lode deposits, in mafic/ultramafic rocks of the ophiolite belt.
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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".