The origin of A-type granites and W-Sn-REE-Nb-Ta mineralization: Insights from geochronology, geochemistry, and Sr-Nd-Pb-Hf-O isotopes of Xiaonanshan granitoids in Guangdong Province, South China
Bibliographic record
Abstract
Abstract The Xiaonanshan W deposit, located in Guangdong Province, South China, is a quartz vein–type deposit that is linked to medium- to fine-grained granite. The ore bodies primarily occur as quartz veins, sulfide-quartz veins, and greisen veins. Zircon U-Pb dating of the fine-grained granite yields an age of 80.04 ± 0.37 Ma, and muscovite from the W-bearing greisen vein provides a 40Ar-39Ar plateau age of 81.01 ± 0.41 Ma. Precise Re-Os dating of molybdenite coexisting with wolframite yields Re-Os model ages for four samples ranging from 81.17 ± 0.92 Ma to 79.27 ± 0.9 Ma, with a weighted mean age of 80.1 ± 1.3 Ma and an Re-Os isochron age of 78.3 ± 2.7 Ma. These geochronological results indicate that both the granite and the associated W mineralization formed simultaneously during the Late Cretaceous. The granite is characterized by high SiO2 contents (72.18–73.45 wt%), elevated total alkalis (Na2O + K2O = 11.35–12.18 wt%), and enriched rare earth elements (REEs; ΣREE = 247.9–294.1 ppm), as well as high Ga/Al ratios (10,000 × Ga/Al = 3.39–3.63). These characteristics classify it as an A-type granite with an A2-subtype affinity. Sr-Nd isotope analyses yield initial 87Sr/86Sr values ranging from 0.7065 to 0.7082, and εNd(t) values from −5.8 to −4.5. Pb isotope compositions show little variation, with 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values ranging from 18.524 to 18.821, 15.704–15.719, and 38.799–39.000, respectively. In situ Hf-O isotope analyses reveal εHf(t) values ranging from −7.16 to +0.88, and uniform δ18O values of 6.2‰ to 7.3‰, suggesting a mixed mantle-crust source. The calculated oxygen fugacity (fO2) values range from FMQ −0.41 to FMQ +1.21. Zircon grains exhibit relatively low Eu/Eu*(0.06–0.12) and Ce/Ce* ratios (2.33–22.87), indicative of low oxygen fugacity. The visible tetrad effect (0.78–0.80), coupled with the presence of abundant Nb-Ta minerals and enriched REEs, suggests strong fractionation and significant W-Sn-Nb-Ta-REE mineralization potential. Additionally, garnet U-Pb dating of the Cu-Pb-Zn–bearing skarn in the deposit’s periphery yields an age of 81.2 ± 2.7 Ma, consistent with the emplacement of the Xiaonanshan granite and associated W-Sn mineralization. This correlation underscores the potential for skarn Cu-Pb-Zn-Sn polymetallic deposits and peripheral vein Pb-Zn-Ag mineralization. The large-scale Cretaceous granitoid magmatism and W-Sn polymetallic mineralization in the region are attributed to lithospheric extension. Further evaluation of the W-Sn, Nb-Ta-REE, and Pb-Zn-Ag mineralization potential of Cretaceous A-type granites in eastern China remains crucial.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".