Silicification of Hydrothermal Gangue Minerals In Pb-Zn-Cu-Fluorite-Quartz-Baryte Veins
Bibliographic record
Abstract
Abstract Late-stage pseudomorphous and perimorphous replacement of euhedral baryte and, to a lesser extent, fluorite and calcite by quartz is a common phenomenon in hydrothermal vein-type deposits. As a consequence of silicification, the primary mineral assemblage might be substantially altered, and therefore this process has a severe negative impact on the economic potential of mineral resources. Although these replacement textures are often reported and have a significant economic importance in mines producing baryte or fluorite of chemical grade, the process that causes this silicification is surprisingly poorly understood. In the present contribution, more than 40 Jurassic–Cretaceous and post-Cretaceous hydrothermal veins from the Schwarzwald mining district, including replacement textures of primary euhedral baryte, fluorite, and calcite, were investigated with respect to their macro- and microscopic textures. It appears that baryte is favorably replaced by pseudomorphs (bladed quartz), while fluorite and calcite are typically replaced by perimorphs. The textures indicate that the mode of replacement of the primary minerals happens continuously and after the initial vein formation. By combining these textural observations with calculated mineral solubilities, a detailed geochemical model has been developed. Existing fluid inclusion data indicate that substantial cooling of the hydrothermal solutions occurs after primary mineral formation. The calculated cooling path reveals opposing solubilities of quartz and the other gangue minerals (baryte, fluorite, and calcite) with decreasing temperature and explains the observed dissolution and precipitation textures. Furthermore, differences in temperature-solubility systematics between baryte on the one hand and fluorite and calcite on the other are responsible for the differences observed in the textures. This agrees with the occurrence of late-stage, low-temperature baryte crystals overgrowing primary baryte assemblages. Conversely, analogous late-stage calcite and fluorite assemblages are only rarely observed. In summary, silicification is a typical cooling effect in various hydrothermal vein-type deposits, but affects different gangue minerals in different ways depending on their temperature-dependent solubility.
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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 | 0.000 | 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) | 0.001 | 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".