Water Content of Opal-A: Implications for the Origin of Laminae in Geyserite and Sinter
Bibliographic record
Abstract
Abstract Sinter and geyserite, formed largely of amorphous opaline silica (opal-A), precipitate at many hot-spring and geyser systems like those found on the North Island of New Zealand. Opal-A is a hydrated silicon dioxide (SiO2.n H2O) that may contain silanols, trapped water, and/or absorbed water. Little is known about the factors that control the distribution of water (H2O + OH) in sinter and geyserite. Backscattered electron images (BSEI) of geyserite and sinter commonly reveal sectors and/or alternating laminae that are characterized by differences in their average atomic weights. Electron microprobe (EMP) and scanning electron microscope (SEM) analyses, however, show that differences in the average atomic weights cannot be attributed to the presence of other elements (e.g., Au, Ag) or minerals (e.g., sulfur, kaolinite, jarosite). The compositional heterogeneity in the opal-A, as highlighted by BSEI, must reflect variation in the water content of the opal-A. Integration of BSEI and EMP analyses for Si and O shows that opal-A contains "excess" O that must be bound into the H2O and OH. The excess O can be used a proxy for the total water (H2O + OH) content of the opal-A that forms geyserite and sinter. Geyserite and sinter from the Whakarewarewa geothermal area is formed of "dry" opal (average 5-6 wt % H2O + OH) and "wet" opal (average 12-13 wt % H2O + OH). Interpretation, based largely on the distribution of these different types of opal in the geyserite and sinter, suggests that the "wet" opal forms as a result of rapid precipitation whereas the "dry" opal forms as a result of slower precipitation. Such information must be integrated into any model that attempts to explain the evolution of geyserite and sinter deposits.
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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 | 0.001 |
| 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 | 0.002 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 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".