Micromorphologies and sulfur isotopic compositions of pyrite in sandstone-hosted uranium deposits: A review and implications for ore genesis
Bibliographic record
Abstract
Serving as an adsorbent and a reductant for the dissolved U, pyrite is abundant and commonly found associated with U minerals in sandstone-hosted U deposits. Different nucleation and growth rates of crystals, sulfur sources and precipitation mechanisms (i.e., biogenic or chemical processes) result in a variety of micromorphologies and a wide range of δ34S values of pyrite under low-temperature conditions. A compilation of 793 published δ34S values ranging from -72.0 to +142.8‰ for pyrite mainly consisting of framboidal, euhedral and cement, and a series of evolved morphologies (i.e., early framboidal, followed by euhedral overgrowth, and finally cements) from sandstone-hosted U deposits across the world is presented here. For the different geographical locations of deposits (e.g., China, USA, Australia and Kazakhstan), the different ages of host sandstones (e.g., Triassic, Jurassic, Cretaceous and Paleogene) and the different morphologies of pyrite (e.g., framboidal pyrite and euhedral + cement pyrite), the distribution characteristics of δ34S values are distinct. Four case studies with comprehensive analyses of micromorphologies, in situ sulfur isotopic compositions as well as trace element contents are discussed to illustrate that pyrite has been employed successfully as a redox proxy to evaluate the genetic model of sandstone-hosted U deposits. The data also implies that during the translation of redox interface, the changes of geochemical characteristics well documented in micro-scale pyrite are responsible for U mineralization.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.005 | 0.005 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".