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According to the temporal-spatial distribution of Neoproterozoic igneous rocks and relative rocks in South China, including ophiolites, arc volcanic and intrusive rocks and subsequent bimodal magmatism, we identified the presence of a Neoproterozoic intra-oceanic arc, continent-arc-continent collision and three tectono-magmatic zones between the Yangtze Block and Cathaysia Block. We have also unraveled the amalgamation and tectono-magmatic histories between the Yangtze and Cathaysia blocks: At ~ 1000-860 Ma, northwestward ocean-ocean subduction and southeastward ocean-continent subduction resulted in the intra-oceanic arc magmatism and active continental margin magmatism in the Cathaysia Block respectively. At ~ 860-825 Ma, the steepening subdution caused development of back-arc basin in the intra-oceanic arc zone and the slab rollback induced the arc and back-arc magmitism in the Cathaysia Block. Meanwhile, a shallow dip northwestward ocean-continent subduction formed active continental margin magmatism in the Yangtze Block. At ~ 825-805 Ma, the continent-arc-continent collision Page 3 of 106 and final amalgamation between the Yangtze and Cathaysia blocks yielded the Jiangnan Orogen. At ~ 805-750 Ma, the Jiangnan Orogen collapsed, and the Nanhua rift basin formed. Our study also rules out any Grenvillian Orogenic event and mantle plume activity in South China and indicates a marginal position of South China in the Rodinia supercontinent.

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Magma mixing commonly takes place between isotopically depleted mafic and enriched felsic magmas. Here we present isotopic evidence exhibiting the opposite behavior in the Early Cretaceous Siling complex (south China), which is composed of gabbro, quartz diorite, granodiorite, and alkali feldspar granite with locally many mafic microgranular enclaves. Field observations and zircon U‐Pb dating indicate that all of the rock units crystallized contemporaneously at ca. 127–129 Ma. Mineralogical and petrochemical analyses indicate that the Siling quartz diorite and granodiorite crystallized from hybrid magmas of temporally and spatially coexisting gabbroic and granitic melts. The Siling gabbro, characterized by variable yet enriched Sr‐Nd‐Hf isotopic compositions [(87Sr/86Sr)i = 0.70788 to 0.70833; ɛNd(t) = −7.6 to −3.5; ɛHf(t) = −6.8 to −1.9], exhibits Th/Nb, Nb/Nb*, and Sm/Yb versus εNd(t) correlations, indicating that the gabbro represents variable mixing of magmas derived from deep‐level pyroxenite and shallow‐level peridotite sources. The Siling alkali feldspar granite, which has typical A‐type characteristics, exhibits less enriched Sr‐Nd‐Hf isotopic signatures [(87Sr/86Sr)i = 0.70650; εNd(t) = −3.2 to −2.5; ɛHf(t) = −1.3] than the coexisting gabbro, indicating its derivation from the remelting of juvenile lower crust. “Reversed isotope” feature of the Siling gabbro and alkali feldspar granite means that the quartz diorite and granodiorite recorded “reversed isotope” mixing between isotopically enriched mafic and relatively depleted felsic magmas. The results indicate that the injection of mantle‐derived mafic magma does not necessarily imprint relatively depleted isotopic signatures on the host felsic melt and that the vertical growth of the continental crust by the input of isotopically enriched magma should be concerned.