Genesis of gold mineralization in southwestern Hunan, Jiangnan Orogen, South China: Insights from sulfide geochemistry and quartz H-O isotopes
Bibliographic record
Abstract
• Invisible gold occurs as lattice-bound in sulfides, while visible gold concentrates along fractures. • Mineralizing fluids were weakly acidic, low-T, and reducing metamorphic hydrothermal solutions. • Mixing of magmatic, metamorphic and meteoric water contributed to Au mineralization. • Sb Enrichment highlights the potential for Au-Sb co-genetic exploration. Recent gold exploration in the Jiangnan orogenic belt, South China, has yielded significant progress, particularly within regions characterized by complex tectonic evolution and magmatic-hydrothermal activity. Despite these advancements, the sources of ore-forming fluids and the genesis of gold deposits in southwestern Hunan, western Jiangnan orogen, remain poorly understood. To address these gaps, this study integrates detailed fieldwork, petrographic investigation, and trace element geochemistry of gold-bearing pyrite and arsenopyrite, alongside hydrogen and oxygen (H-O) isotopic compositions of quartz, from four representative gold deposits: Taojinchong, Yangwantuan, Mobin and Xinhuang Mibei. Pyrite from these deposits exhibits a range of elemental concentrations: very low to low (< 0.1–10 ppm) for Zn, Mo, Bi, Co, Cu, Sb, Au, Ni and Pb; moderate concentrations (10 to 1,000 ppm) for Ge, Ni, Pb, Co, Cu, Sb and Au; and elevated concentrations (> 1,000 ppm) for As. Arsenopyrite crystals show very low to low concentrations (< 0.1–10 ppm) of elements such as Cu, Zn, Ag, Co, Mo, Te, Bi, Ni, Au and Pb; intermediate concentrations (10 to 1,000 ppm) of Ge, Ni, Au, Pb, Co, Te; and extremely high concentrations (> 1,000 ppm) of Sb. The δD fluid values vary from –72.3 ‰ to –48.9 ‰, while the δ 18 O fluid values range from 0.3 ‰ to 4.6 ‰. Gold occurs in both visible and invisible forms, with the latter predominantly existing as lattice-bound gold in pyrite and arsenopyrite crystals. The findings revealed that gold transport occurred primarily as complexes (e.g., Au(HS) 2 – and AuH 3 SiO 4 ) within weakly acidic, low-temperature, and reducing metamorphic-hydrothermal fluids. We propose that metamorphic-hydrothermal fluids were the primary source of ore-forming fluids during the mineralization process, accompanied by late-stage influx of meteoric water. The pronounced enrichment of Sb in these mineralizing fluids highlights a potential genetic association between Au and Au-Sb deposits in the Jiangnan Orogenic Belt, offering new exploration targets in analogous collisional orogens.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".