Petrogenesis and Mineralization Potential of the Early Silurian Syenogranites in the Yama Beryllium Deposit Within the Tataleng Granitic Batholith, Qilian Orogen, NW China: Insights from U-Pb Geochronology and Geochemistry

Recently, significant beryllium mineralization was discovered along faults within syenogranites in the Yama area of the Qilian Orogen, NW China. This study presents a comprehensive analysis of the geochemical compositions of these syenogranites, along with zircon U–Pb geochronology, Hf isotopic data, and trace element analyses. Barren and beryllium-bearing syenogranites yielded weighted mean 206Pb/238U zircon ages of 437.7 ± 3.3 Ma and 432.0 ± 2.3 Ma, respectively, indicating a consistent emplacement age in the early Silurian. Their geochemical characteristics are slightly peraluminous, with high alkali contents; relatively low (K2O + Na2O)/CaO and Fe2O3T/MgO ratios, low concentrations of Zr + Nb + Ce + Y, strongly negative Eu anomalies, high Rb/Sr and Rb/Ba ratios, and negative correlations between Rb and Th, all indicative of fractionated S-type syenogranites. Furthermore, geochemical data combined with negative zircon εHf(t) values suggest derivation from the partial melting of Paleoproterozoic pelitic-rich protoliths within a relatively shallow, reworked lower crust during an early Silurian syn-collisional setting. Negative ΔFMQ values and low Ce4+/Ce3+ ratios, along with relatively high La contents and SmN/LaN ratios in a few zircon grains, as well as relatively low whole-rock Nb/Ta and Zr/Hf ratios, imply a certain initial-stage magmatic–hydrothermal beryllium-mineralization potential for the studied syenogranites.