From Arc to Delamination: Episodic Magmatism and Porphyry Cu–(Mo–Au) Systems in the Sanjiang Tethyan Orogenic Belt, Southwestern China

ABSTRACT Porphyry Cu(MoAu) deposits are economically critical mineral resources that form under complex geodynamic regimes, particularly within collisional orogenic belts such as the Sanjiang Tethyan orogen in southwestern China. Here, we combine new zircon UPb geochronology and LuHf isotopes with a curated compilation of whole‐rock geochemistry and SrNdO isotope analyses to construct a high‐resolution temporal–spatial framework of multiphase magmatic evolution and associated metallogenesis across the belt. Three distinct magmatic–metallogenic episodes are recognised: (1) Late Triassic, subduction‐related hybrid magmatism (235–206 Ma); (2) Late Cretaceous, post‐collisional crustal anatexis (88–76 Ma); and (3) Paleogene, post‐collisional hybridisation driven by lithospheric delamination and/or lower‐crustal foundering (45–32 Ma). Each episode is characterised by unique magma sources, redox conditions, and crust–mantle interactions, which collectively control melt fertility and ore‐forming efficiency. Elevated Sr/Y ratios, depleted Y and Yb contents, and variable εNd(t) and εHf(t) isotopic signatures reflect partial melting and deep differentiation within garnet±amphibole stability fields at deep crustal levels. Where two or more independent proxies concur, the conditions are consistent with relatively oxidised, H 2 O‐rich magmas. Our findings highlight the pivotal role of deep lithospheric processes in generating ore‐fertile magmas and establish a coherent geodynamic framework for porphyry deposit formation in collisional orogens, providing important implications for mineral exploration in comparable geological settings globally. This study also offers exploration guidelines for porphyry systems in post‐collisional orogenic belts worldwide, enhancing its applicability beyond the Sanjiang region.