Pedogenic origin of Mezezo opal hosted in Ethiopian Miocene rhyolites
Bibliographic record
Abstract
ABSTRACT Opals are widespread within Miocene volcanic sequences in the North Shoa province of Central Ethiopia. The opal occurs as cavity fillings in a 5 m thick seam of glassy rhyolitic ignimbrite that is sandwiched between basaltic lava flows. The opals occur over a large area (>25 km2). X-ray diffraction analyses show that they are CT-type. The opals contain lower concentrations of trace elements (up to 100 times) than the host rhyolite. Ratios of most trace elements are, however, similar in both the opals and rhyolites. The opals have high δ18O values (28.4–33.8‰) that imply a low temperature of formation, between 20.55 and 25.74 °C. We therefore propose that the opals precipitated from meteoric waters that had percolated through and interacted with the host rhyolite. Field evidence indicates that this weathering and alteration occurred immediately after emplacement of the rhyolites, but prior to the extrusion of the overlying basalt flows.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 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) | 0.002 | 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".