Geochronological, geochemical and isotopic constraints on the genesis of Cu mineralization in the giant Zhuxi W–Cu deposit, South China

Abstract

The reported coexisting Cu and W mineralization of economic significance in single ore deposit worldwide is rare. However, both Cu and W mineralization have been discovered in the giant Zhuxi W-Cu deposit in South China. To address the genetic relations between the shallow Cu and deep W mineralization in this giant ore system, here we report U-Pb dating, trace element and Hf isotope data of zircon from the Cu-related granodiorite porphyry, U-Pb dating and trace element data for hydrothermal titanite and S isotopic data for sulfide related to Cu mineralization. The U-Pb ages of zircons from two granodiorite porphyry samples are 155.7 ± 0.8 Ma and 152.5 ± 0.7 Ma, respectively, which are consistent with the U-Pb age of the hydrothermal titanites of 154.5 ± 5.0 Ma, suggesting that the shallow Cu mineralization formed in the late Jurassic and was simultaneously associated with the deep giant W mineralization at Zhuxi. Trace element composition of titanites favor a high fH₂O and relatively low fO₂ environment for Cu formation. Sulfides exhibit δ³⁴S values ranging from –0.9 ‰ to 3.5 ‰, indicating a magmatic origin. Zircons from the granodiorite porphyry present ε_Hf(t) values of − 9.9 to 1.3, suggesting that the Cu ore-related granodiorite magmas were derived mainly from the partial melting of Cu-enriched metavolcanoclastic rocks with minor mantle sources. Trace element composition of zircons indicate a magma mixing process with high-temperature melts > 750 °C that are relatively rich in Y, Th and rare earth elements but with lower Hf concentrations, being added to relatively low-temperature ∼ 700 °C crustal-derived granodiorite magmas. Combining the above data and previously determined zircon Lu–Hf isotopes, we propose that the Cu and W in Zhuxi may have been derived mainly from the partial melting of Cu-enriched metavolcanoclastic rocks and W-enriched metasedimentary sequences of the Neoproterozoic juvenile crust, respectively. The intrusion of the Cu-related granodiorite porphyry should have been triggered by the upwelling of heated mafic magmas from the asthenospheric mantle during the Late Jurassic lithospheric compressional–extensional conversion stage.