Geochemical Characteristics and Sources of Ore‐forming Fluids of the Mayuan Pb‐Zn Deposit, Nanzheng, Shaanxi, China
Bibliographic record
Abstract
The Mayuan stratabound Pb‐Zn deposit in Nanzheng, Shaanxi Province, is located in the northern margin of the Yangtze Plate, in the southern margin of the Beiba Arch. The orebodies are stratiform and hosted in breciated dolostone of the Sinian Dengying Formation. The ore minerals are primarily sphalerite and galena, and the gangue minerals comprise of dolomite, quartz, barite, calcite and solid bitumen. Fluid inclusions from ore‐stage quartz and calcite have homogenization tempreatures from 98 to 337°C and salinities from 7.7 wt% to 22.2 wt% (NaCl equiv.). The vapor phase of the inclusions is mainly composed of CH4 with minor CO2 and H2S. The δDfluid values of fluid inclusions in quartz and calcite display a range from –68‰ to –113‰ (SMOW), and the δ18Ofluid values calculated from δ18Oquartz and δ18Ocalcite values range from 4.5‰ to 16.7‰ (SMOW). These data suggest that the ore‐forming fluids may have been derived from evaporitic sea water that had reacted with organic matter. The δ13CCH4 values of CH4 in fluid inclusions range from –37.2‰ to –21.0‰ (PDB), suggesting that the CH4 in the ore‐forming fluids was mainly derived from organic matter. This, together with the abundance of solid bitumen in the ores, suggest that organic matter played an important role in mineralization, and that the thermochemical sulfate reduction (TSR) was the main mechanism of sulfide precipitation. The Mayuan Pb‐Zn deposit is a carbonate‐hosted epigenetic deposit that may be classified as a Mississippi Valley type (MVT) deposit.
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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 | 0.002 |
| Science and technology studies | 0.001 | 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".