Zircon geochronology, geochemistry, and Hf isotopes of granites in the Yazigou skarn Cu–Pb–Zn deposit: Insights into Triassic skarn mineralization potential in the Qimantagh area, Qinghai Province, NW China

Abstract

The Triassic period has been suggested to be the main metallogenic epoch in the Qimantagh area of Qinghai Province. However, the porphyry copper mineralization potential of this region remains poorly constrained. Here we present zircon U–Pb ages, trace-element data, and Hf isotopic compositions from granites in the Yazigou skarn Cu–Pb–Zn deposit. The zircon U–Pb age of the mineralization-related K-feldspar granitic porphyry at Yazigou is 230 ± 2 Ma, whereas the granodiorite yields an age of 416.7 ± 4.2 Ma. The K-feldspar granitic porphyry exhibits ε_Hf(t) values of -0.4 to +4.0 and two-stage Hf model ages (T_DM2) of 1.0–1.3 Ga, suggesting derivation from melting of Mesoproterozoic to crust, accompanied by minor contributions from mantle material. Zircon trace element signatures further indicate highly magmatic oxygen fugacity (ΔFMQ = +1.0 to +2.3), consistent with typical of oxidized skarn systems. The extremely low Eu anomalies (0.01–0.03) suggest that the magma system underwent intense plagioclase fractional crystallization, implying a low water content. Although the Yazigou deposit shares a similar magma source with other metallic deposits in the Qimantagh region, comparison with the Eu anomalies of Tibet porphyry Cu deposits suggests that the low water content resulted in its limited mineralization potential.