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Numerous late Paleoproterozoic to early Mesoproterozoic mafic magmatic rocks are exposed in the southwestern Yangtze Block, corresponding to early breakup of the Nuna supercontinent. Geochronological data reveal three episodes of mafic magmatism at ~1,740, 1,700, and 1,500 Ma. The two older generations have MORB‐like Nb/Ta ratios and superchondritic Nd‐Hf isotopes, indicating that they were likely derived from partial melting of asthenospheric mantle. In contrast, the ~1,500 Ma mafic rocks possess OIB‐like Nb/Ta (16.7–19.1) and Zr/Hf (41.0–45.1) ratios, εNd (t) values (−0.8 to +0.1), and εHf (t) values (−3.3 to +8.4), suggesting that they originated from a mantle plume. These three pulses of mafic magmatic activity in the Yangtze Block have geochemical features (such as TiO2 contents, Nb/Y, and La/Yb values), similar to coeval mafic rocks in Siberia and Laurentia, consistent with detrital zircon provenance studies, which show a spatial linkage of the Yangtze Block with northern Laurentia in the Nuna configuration. Taking all synchronous mafic magmatism into account, a mantle plume beneath southern Siberia was considered to be initiated at ~1,750 Ma forming a broad region of mafic magmatism that extended into the Yangtze Block as well as beneath northern Laurentia and resulted in lithospheric extension. The Yangtze Block was possibly the nearest neighbor to northwestern Siberia at ~1,500 Ma and subsequently drifted from the Nuna supercontinent induced by the ~1,500 Ma Kuonamka mantle plume, heralding a period of limited magmatic activity and tectonic quiescence in the Yangtze Block that extended throughout the remainder of the Mesoproterozoic. Key Points: Three episodes of mafic magmatism (~1,740, 1,700, and 1,500 Ma) in the Yangtze Block were associated with breakup of the Nuna supercontinentFar field extensional setting beneath the Yangtze Block was possibly induced by ~1,750 Ma Timpton mantle plume beneath SiberiaThe Yangtze Block was finally separated from the Nuna supercontinent associated with the upwelling ~1,500 Ma Kuonamka mantle plume [ABSTRACT FROM AUTHOR]

It is debated whether global-scale tectono-magmatic quiescence prevails on the Earth during the early Paleoproterozoic. The early Paleoproterozoic meta-mafic and intermediate rocks in the southwestern Yangtze Block of South China could provide an opportunity to constrain not only the tectonic evolution of the Yangtze Block itself but also augment our understanding of the global tectono-magmatic lull during the early Paleoproterozoic. Zircon U Pb geochronological study indicates that the meta-mafic rocks were emplaced at ca. 2.32 Ga, whereas the intermediate rocks were emplaced at ca. 2.35 Ga. These two lithologies are characterized by subduction-related whole-rock geochemical (such as depleted Nb, Ta and enriched Rb, K, Pb) and unradiogenic Nd Hf isotopic signatures (ε Hf (t) < 0, ε Nd (t) < 0), implying a derivation from a geochemically enriched lithospheric mantle modified by ancient subduction. Thermodynamic modeling further suggests that the intermediate rocks are products of the AFC process between mantle-derived basaltic magma and TTG-like basement rocks at shallow crustal levels. We interpret this as occurring within a post-orogenic extensional setting. Integrated with the published work, we further posit that the Yangtze Block experienced a tectonic regime transition from compressive orogenesis to post-orogenic extension during the early Paleoproterozoic, and the magmatic activities in several crustal blocks are still active until ~2.3 Ga and therefore places important constraints on the beginning of the tectono-magmatic lull. [Display omitted] • 2.35–2.32 Ga mafic-intermediate magmatism is identified in the SW Yangtze Block. • Mafic-intermediate rocks in this study were derived from the lithospheric mantle. • Tectonic transition from orogeny to post-orogenic extension at ~2.35 Ga in Yangtze. [ABSTRACT FROM AUTHOR]