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The Pingtan and Tonglu igneous complexes in SE China are typical of the calc-alkaline series developed at active continental margins. These two complexes are dominated by felsic rocks, temporally and spatially associated with minor mafic rocks. Morphological and trace-element studies of zircon populations in rocks from each of these complexes show that the zircon populations may be divided into 3–4 distinct growth stages, characterized by different distributions of morphological indices (Ipr, Ipy and Iel), and different contents of the substituting elements (Hf, U, Th, Y and P). The four growth stages recognized in the zircons are believed to have formed successively in the magma chamber, during the emplacement, and in the early and later stages of magma consolidation, respectively. All four stages are recognized in the plutonic Pingtan complex, whereas the stages 3 and 4 are less developed in the volcanic/subvolcanic Tonglu complex. Based on the chemistry and morphology of the different zircon populations of the Pingtan and Tonglu complexes, it is suggested that basaltic magmas underplating at the boundary between crust and mantle caused partial melting of the mid–lower crust and produced granitoid magmas. Subsequently, mixing between magmas was important.

The identification of Late Carboniferous (317 ± 3 Ma) Daixi‐Wufenglou S‐type granites and Early Triassic (247 ± 2 Ma) Houzhang complex (comprising monzodiorite and monzogranite) in southeast China provides new insights into the bewildering tectonics of south China, before its final welding to the Eurasian continent. The Daixi‐Wufenglou granites have high K2O (4.01–6.54 wt%), A/CNK (1.02–1.34), high bulk initial 87Sr/86Sr (0.7094–0.7160) and low εNd(t) (−8.87 to −6.31), and low zircon εHf(t) (−8.1 to −1.9) and high δ18O (12.7–14.0‰), indicating derivation by partial melting of a Neoproterozoic basement as a result of the input of mantle‐derived heat in a back‐arc extensional setting, triggered by rollback of the Paleo‐Pacific plate subduction beneath the outboard proto‐Japan arc. The monzodiorites are shoshonitic, characterized by high K, Ni, Cr, and Mg#, and the monzogranites are adakitic, defined by high Sr/Y, (La/Yb)n and low Y, Yb. They have similar 87Sr/86Sr (0.7085–0.7087), εNd(t) (−5.92 to −5.34), and εHf(t) (−7.5 to −2.5), indicating their petrogenetic linkage. The monzodiorites and monzogranites represent early crystallization phases (cumulates) and residual melts of a mantle‐derived magma, generated from a metasomatically enriched mantle. Integrating these data with other geological information from south China and neighboring countries, we propose a new model for the tectonic evolution of the Late Paleozoic south China, which was controlled by the subduction of the Paleo‐Pacific Ocean plate. A distal continental back‐arc setting was produced by slab rollback in the early stages, and an active continental margin environment was produced by the accretion of the proto‐Japan arc in the later stages.