MINERALOGY, MINERAL COMPOSITIONS AND FLUID EVOLUTION AT THE WENZEL HYDROTHERMAL DEPOSIT, SOUTHERN GERMANY: IMPLICATIONS FOR THE FORMATION OF KONGSBERG-TYPE SILVER DEPOSITS
Bibliographic record
Abstract
The post-Variscan Wenzel vein-type deposit near Wolfach, in the Black Forest, Germany, the type locality of the Ag–Sb alloy dyscrasite, was investigated by ore microscopy, electron-microprobe analysis, stable isotope and fluid-inclusion analysis. Three stages of mineralization could be distinguished. Whereas the first stage is a typical sulfide mineralization including galena and tetrahedrite, the second and third stage show a sulfide-poor association of Ag–Sb alloys, as well as Fe, Co and Ni arsenides and sulfarsenides, in a calcite matrix. The main ore minerals of this stage are allargentum and dyscrasite. The microprobe data for the diarsenides show extensive, and partly hitherto undocumented, solid solution in Fe–Co–Ni space. Seven distinct generations of calcite were distinguished. The δ13C (V–PDB) and δ18O (V–SMOW) values of these generations show a positively correlated trend that evolves from −13.0 to −4.0‰ and from 12.3 to 23.6‰, respectively. Fluid-inclusion data of stage I show homogenization temperatures of 100–180°C at salinities of 17–26 wt.% NaCl eq. Fluid inclusions in stage-II calcite display similar, but more restricted values, 110–150°C and 25–28 wt.% NaCl eq., respectively. The stage-III fluid inclusions show similar temperatures of homogenization, but different salinities. Earlier calcite of this stage contains inclusions with salinities of 27–30 wt.% NaCl eq., whereas later calcite has lower salinities, 3–10 wt.% NaCl eq. The initial temperatures of ice melting of most fluid inclusions range between −45 and −60°C and are typical of an H2O–NaCl–CaCl2 fluid. On the basis of all available geochemical data and phase-equilibrium constraints, we favor a model in which basement-derived near-neutral-pH hydrothermal fluids remobilized older products of mineralization. Mixing of these fluids with more alkaline formation-waters from the Mesozoic cover rocks resulted in the precipitation of the silver alloys in an enrichment zone at P–T conditions of 120–150°C and approximately 200 bars. A significant shift in pH from near-neutral to alkaline can explain the abundant association of silver alloys with calcite gangue and the general absence of quartz in the enriched ore zone. This conceptual model can be applied to similar ore deposits worldwide, where rich silver ores are hosted by calcite-rich and quartz-poor assemblages of gangue minerals.
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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 | 0.001 | 0.001 |
| 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".