Deep-Seated Processes Controlling Mesozoic Differential Metallogeny in the Southern Region of South China: Insights from Hf-Nd Isotope Mapping

The southern region of the South China Block hosts a super-large metallogenic province. However, the Mesozoic differential metallogeny between the southern Cathaysia Block (W-Sn) and the southern Yangtze Block (Au-Sb) remains enigmatic. To characterize the crustal architecture beneath different metallogeny belts, we integrate 3239 published εHf(t) values of synmagmatic zircons from Mesozoic igneous rocks and corresponding whole-rock εNd(t) datasets to generate coupled Hf–Nd isotopic mappings. The results show that εHf(t) values range from −19.3 to +11.6 (TDM2: 464–2419 Ma) and εNd(t) values are from −12.2 to +5.0 (TDM2: 580–2008 Ma) in the southern part of South China Block. High εHf(t) (−4~+11.6) and εNd(t) (−4~+5.0) zones are concentrated along the Honghe Fault and Chenzhou–Linwu Fault systems, while low-value Hf–Nd isotopic (εHf(t) = −10.6 to −4; εNd (t) = −12.2 to −4) zones are mainly distributed in the interior of the southern Yangtze Block. The W-Sn deposits in the southern Cathaysia Block are genetically linked to the heterogeneous εHf(t)-εNd(t) isotopic domains. The ore-forming materials of these high-temperature W-Sn polymetallic deposits may primarily derive from crust hybrid magmas that have undergone multistage crustal reworking. In contrast, low-temperature Au-Sb deposits in the northern Youjiang basin are distributed in areas characterized by elevated εHf(t)-εNd(t) isotopic signatures, which are primarily derived from reworked crust with significant mantle contributions. Most magmatic rock-associated Au deposits tend to cluster at the boundaries of Hf-Nd isotopic anomalies, which indicates the contribution of crust-mantle interaction to Au mineralization. Our Hf-Nd isotopic mappings reveal that mantle-crust deep-seated process controls the Mesozoic differential metallogeny between the southern Cathaysia Block (W-Sn) and the southern Yangtze Block (Au-Sb).