Silver Behavior During Magmatic and Magmatic-Hydrothermal Evolution of a Highly Evolved Reduced Granitic System Related to the Giant Shuangjianzishan Ag-Pb-Zn-(Sn) Epithermal Deposit, Northeast China
Bibliographic record
Abstract
Abstract Magmatic-related epithermal silver-rich polymetallic deposits are among the most important sources of Ag in the world, and they are found associated with magmatic systems with striking differences. Most of the time, they are associated either with I-type oxidized (magnetite-series granite) intermediate to evolved intrusions or with S-type/A-type reduced (ilmenite-series granite) highly evolved intrusions. To better understand these associations, the Ag evolution has been tracked during the magmatic differentiation and the magmatic-hydrothermal transition stage of A-type highly evolved porphyritic granites associated with the giant Shuangjianzishan Ag-Pb-Zn-(Sn) epithermal deposit, the largest known Ag deposit of Asia (145 million tonnes at 128.5 g/t Ag and 2.2 wt % Pb + Zn) located in the largest known metallogenic province for Ag in China (the southern Great Xing’an Range). At the Shuangjianzishan deposit, the porphyritic granite complex consists of three temporally distinct intrusions—a coarse-grained monzogranite porphyry, a fine-grained syenogranite porphyry, and a fine-grained syenogranite—having crystallized at ~2 kbar and ~750°C and recording a continuous magmatic differentiation trend. The silicate melt that generated the last highly differentiated intrusion (fine-grained syenogranite) is interpreted as the source of the mineralizing fluids forming the Shuangjianzishan Ag-Pb-Zn-(Sn) epithermal deposit, as it is the only intrusive unit that reached fluid saturation, as indicated by cotrapped fluid and melt inclusions in quartz phenocrysts and by the occurrences of unidirectional solidification textures (USTs). Silver evolution in the different porphyritic granite facies was reconstructed with laser ablation-inductively coupled plasma-mass spectrometry analyses of quartz-hosted silicate melt inclusions, amphibole-hosted magmatic sulfide inclusions, and chemical modeling. The silicate melt forming the porphyritic granite complex was sulfide saturated during the first crystallization stage, as shown by the occurrence of Ag-rich monosulfide solid solution (MSS) inclusions hosted in amphibole phenocrysts from the coarse-grained monzogranite porphyry and from mafic microgranular enclaves hosted in the coarse-grained monzogranite porphyry. However, these Ag-rich MSSs had only a minimal impact on the Ag budget of the magmatic system, as shown by the increase of the Ag concentration (~100–1,000 ppb) in quartz-hosted silicate melt inclusions during the further evolution of the system until fluid exsolution was reached. These results combined with mass balance modeling suggest that Ag and Sn are efficiently transferred to the evolving residual melt during crystallization and crystal-melt segregation. The results of this study indicate that highly Ag endowed epithermal polymetallic deposits can be formed from the exsolution of Ag-rich mineralizing fluids from relatively low volume, highly evolved, reduced melts, similar to those responsible for the formation of Sn-rich greisen deposits.
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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) | 0.003 | 0.001 |
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; both teacher heads agree on what is shown here.
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".