Platy Galena from the Viburnum Trend, Southeast Missouri: Character, Mine Distribution, Paragenetic Position, Trace Element Content, Nature of Twinning, and Conditions of Formation
Bibliographic record
Abstract
The Viburnum Trend of southeast Missouri is one of the world’s largest producers of lead. The lead occurs as galena, predominantly in two crystallographic forms, octahedrons and cubes. Many studies have shown that octahedral galena is paragentically early, the more abundant of the two crystal forms, and is commonly modified in the cube. Those studies also have shown that the cubic form is paragenetically later, less abundant than the octahedrons, and may exhibit minor octahedral modifications. Viburnum Trend galena crystals that exhibit a platy form have received almost no study. The reason for their lack of study is the rarity of their occurrence. This communication discusses their character, mine distribution, paragenetic position, trace element contents, nature of twinning, and speculated conditions of formation. It also compares their character to similar platy galena occurrences in Germany, Bulgaria, Russia, Mexico, and notes their occurrence at the Pine Point District in the Northwest Territories of Canada and at the Black Cloud mine in Colorado. Flat, platy galena crystals have been recognized to occur in very small amounts in the Magmont, Buick, Fletcher, Brushy Creek, and Sweetwater mines in the Viburnum Trend. In contrast, platy galena has never been observed to occur at the Casteel, West Fork, #27, #28, and #29 mines in the Trend. The platy crystals have formed early in the paragenetic sequence of the ores, prior to and coated by subsequently deposited druzy quartz and cubic galena. Spinel twinning of the octahedron produces flat platy crystals. The platy galena crystals of the Viburnum Trend are very similar in crystal morphology to platy galena crystals interpreted to be spinel twins in the Gonderbach Ag mine in NW Germany, the Dalnegorsk Pb-Zn (skarn deposit) mine in SE Russia, the Madan ore field of skarn Pb-Zn-Ag deposits of southern Bulgaria, and the large Naica skarn Pb mine of northern Mexico. The crystallization of certain crystal forms of galena has been ascribed to the incorporation of elevated contents of trace elements in some lead districts. Analysis of Viburnum platy galena crystals shows that they contain very low levels of trace elements: 3.1 ppm Ag, <2 ppm Bi, <2 ppm Sb, and <2 ppm As. Thus, elevated trace element content is not the cause for the development of Viburnum platy galena. It is speculated that the Viburnum spinel-twinned galena crystals were the result of rapid crystallization from oversaturated hydrothermal ore fluids.
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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) | 0.004 | 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".