Trace Element Distribution (Cu, Ga, Ge, Cd, and Fe) IN Sphalerite From the Tennessee MVT Deposits, USA, By Combined EMPA, LA-ICP-MS, Raman Spectroscopy, and Crystallography
Bibliographic record
Abstract
Abstract The zinc mines of Tennessee are known to contain high concentrations of certain trace elements (Cu, Ga, Ge, Fe, and Cd). Here, we investigate and compare sphalerites from two mining districts in the center (Central Tennessee Mines: CT) and east (East Tennessee Mines: ET) of Tennessee in order to (1) understand the substitution mechanisms that control the incorporation of trace elements in sphalerite, and (2) relate these mechanisms to the conditions of metal deposition. Electron microprobe and LA-ICP-MS analyses reveal complex chemical zoning in the sphalerites together with coupling of two main groups of trace elements: copper, germanium, and gallium; and iron and cadmium. The zoning is interpreted in terms of substitution mechanisms using different equations, including those previously described, such as 2Cu + + Ge 4+ ↔ 3Zn 2+ , Cu + + Ga 3+ ↔ 2Zn 2+ , Fe 2+ + Cd 2+ ↔ 2Zn 2+ , as well as new equations involving Ge 2+ and vacancies: Ge 2+ ↔ Zn 2+ , □ + Ge 4+ ↔ 2Zn 2+ , and □ + 2Ga 3+ ↔ 3Zn 2+ . Electron microprobe analyses of euhedral crystals of sphalerite highlight a correlation between the presence of trace elements and preferential crystallographic growth directions: copper and germanium are preferentially incorporated along the [010] growth direction, while cadmium is preferentially incorporated along the [110] growth direction. Raman spectroscopy highlights for the first time the possible coexistence of two different crystallographic forms of ZnS in some samples: cubic sphalerite and a non-cubic form, possibly a wurtzite-type structure. This is supported by the LA-ICP-MS data, which demonstrates a relationship between the trace element content and crystallographic structure: the non-cubic form of ZnS is enriched in copper, germanium, and gallium, while iron and cadmium are the most abundant trace elements in the cubic sphalerite. Although most of the main substitution mechanisms are observed in sphalerites from the two mining districts, the sphalerites differ in terms of their germanium grade and valency. These differences can be interpreted both in terms of fluid composition and redox conditions, suggesting that two different episodes of mineralization occurred in Tennessee.
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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 | 0.002 | 0.001 |
| 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".