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Neoproterozoic magmatic rocks and detrital zircons with low-delta O-18 values were frequently identified in the Yangtze Block, Madagascar, and India. Here we first report Neoproterozoic low-delta O-18 zircons from the central part of the Cathaysia Block in South China. These zircons include detrital grains from the Early Paleozoic metamorphic rocks, inherited domains from the Early Paleozoic granitic rocks, and igneous ones from the Neoproterozoic volcanic rocks. In combination with the available data for Neoproterozoic O-18-depleted magma and zircons worldwide, we conclude that, globally, O-18-depleted magmatic activities generally began after 800 Ma and reached the peak at 780-760 Ma, corresponding to the rifting of Rodinia supercontinent. The occurrence of low-delta O-18 magmatism after approximately 730 Ma in the northern Yangtze Block possibly indicates extended rifting that was associated with Neoproterozoic glaciations. The similarity in low-delta O-18 magmatism between northwest India, Madagascar, and South China suggests close connections in the Rodinia supercontinent during the middle Neoproterozoic.

Plain Language Summary Low-delta O-18 magma has received great attention and it has profound implications on geological and climate evolution. Neoproterozoic era is a unique period to breed low-delta O-18 magmas and snowball Earth. This manuscript first report Neoproterozoic moderately O-18-depleted zircons from the central part of the Cathaysia Block in South China, and it builds a four end-member Hf-O isotopic mixing model to explain the global low-delta O-18 magmas at Neoproterozoic era. Our compilation of low-delta O-18 zircon data and our new data confirms that globally Neoproterozoic O-18-depleted magmatic activities generally began after 800 Ma and reached a peak at 780-760 Ma. This provides new information on the rifting of Rodinia supercontinent and suggests close connections between northwest India, Madagascar, and South China in the Rodinia supercontinent. This manuscript deals with the hot-debated topics on oxygen isotopes and supercontinent cycle. We believe that this manuscript will attract international readers from a wide scope of geosciences.