ABSTRACT The Peigang intrusive complex, located at the margin of the Luzong Basin in the Middle‐Lower Yangtze Metallogenic Belt, is mainly composed of pyroxene diorite and pyroxene monzodiorite porphyry, which exhibit transitional contacts and similar geochemical signatures. Zircon U–Pb dating yields an age of ~131 Ma, indicating emplacement during the Early Cretaceous magmatic event in the region. Both pyroxene diorite and pyroxene monzodiorite porphyry show adakitic affinities, characterised by high Sr/Y and La/Yb ratios and relatively low SiO 2 contents (< 56 wt%). Zircon ε Hf ( t ) values ranging from −8.2 to −4.5 suggest derivation from a lower crustal source. Compared with the adjacent Shaxi intrusion, which is genetically associated with porphyry Cu–Au mineralisation, the Peigang intrusion displays a more crustal signature and lower oxidation state (ΔFMQ −1.8 to 0). These characteristics likely account for its limited porphyry Cu–Au mineralisation potential, despite minor chalcopyrite occurrences. This comparison underscores the critical role of mantle‐derived magma input in controlling magma fertility and the formation of porphyry Cu–Au deposits in the Middle‐Lower Yangtze Belt.
TU et al. (Tue,) studied this question.