Geochemistry and formation of agate-bearing lithophysae in Lower Permian volcanics of the NW-Saxonian Basin (Germany)
Bibliographic record
Abstract
Abstract Geochemical and mineralogical investigations of the Lower Permian Kemmlitz rhyolite within the NW-Saxonian Basin (Germany) and associated lithophysae (high-temperature crystallization domains) as well as agates were carried out to constrain the genesis and characteristics of these volcanic rocks and the origin of the agate-bearing lithophysae. The volcanic rocks of rhyolitic composition are dominated by quartz, sanidine, and orthoclase and most likely derive from lava flows. Agate-bearing lithophysae were exclusively formed in a glassy facies (pitchstone) of the rhyolites, which was afterwards altered to illite-smectite mixed-layer clays. The results of this study show that agate formation can be related to the alteration of the volcanic rocks accompanied by the infill of mobilized silica into cavities of lithophysae. Fluid inclusion studies point to temperatures of agate formation above 150 °C, indicating that the mobilization and accumulation of silica started already during a late phase of or soon after the volcanic activities. Remarkable high concentrations of B (29 ppm), Ge (> 18 ppm), and U (> 19 ppm) as well as chondrite-normalized rare earth element (REE) distribution patterns of the agates with pronounced negative Eu-anomalies, slightly positive Ce-anomalies and enriched heavy rare earth elements (HREE) indicate interactions of the host rocks and transport of SiO 2 with magmatic volatiles (F/Cl, CO 2 ) and heated meteoric water. Characteristic yellow cathodoluminescence (CL), heterogeneous internal textures as well as high defect density of micro- and macrocrystalline quartz detected by electron paramagnetic resonance (EPR) spectroscopy point to crystallization processes via an amorphous silica precursor under non-equilibrium conditions.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 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) | 0.000 | 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 teacher head, 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".