Neoproterozoic magmatic rocks and detrital zircons with low‐δ18O values were frequently identified in the Yangtze Block, Madagascar, and India. Here we first report Neoproterozoic low‐δ18O 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 18O‐depleted magma and zircons worldwide, we conclude that, globally, 18O‐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‐δ18O magmatism after approximately 730 Ma in the northern Yangtze Block possibly indicates extended rifting that was associated with Neoproterozoic glaciations. The similarity in low‐δ18O magmatism between northwest India, Madagascar, and South China suggests close connections in the Rodinia supercontinent during the middle Neoproterozoic.

Silicic igneous rocks in the oceanic crust provide insights into the formation of proto‐continental crust, which can be investigated by studying rare silicic rocks within ophiolite complexes. This study focuses on plagiogranites that crop out as lenses and blocks in the northeast Jiangxi ophiolite (NJO), located in the eastern segment of the Neoproterozoic Jiangnan Orogen, southern China. The plagiogranites yield a mean SHRIMP U‐Pb zircon crystallization age of ca. 995 Ma and also record a late thermal event at ca. 220 Ma. The plagiogranites have high Na, very low K, and highly variable rare earth element (REE) concentrations from extremely depleted total REEs to strong enrichment in light REEs. Some samples have adakitic characteristics. Zircons from the plagiogranites have positive εHf(t) values (9.96 to 16.6) and mantle‐like δ18O values (5.13 ± 0.21‰), indicating a juvenile crustal or mantle source. Based on REE modeling, we propose a two‐stage model for the formation of the geochemically variable NJO plagiogranites: (1) High‐REE adakitic magmas plagiogranites were generated by 20% partial melting of basaltic oceanic crust; and (2) subsequent fractional crystallization (up to 50%) of these magmas and crystal accumulation produced the low‐REE plagiogranites. Our results show that granitic magmas can become highly differentiated in an oceanic setting. The diversity of silicic rocks in the oceanic crust is mainly the result of partial melting of subducted basaltic rocks and subsequent differentiation rather than just fractional crystallization of basaltic magmas.

Copper Catalyzed Decarboxylative Alkynylation of Quaternary α-Cyano Acetate Salts. -The title reaction is utilized for the preparation of functionalized butynenitriles. Alkyne chlorides show a comparable reactivity, but α-cyanoacetates containing active H like (IVb) fail to give the desired coupling product. -(FENG, Y.-S.; XU, Z.-Q.; MAO, L.; ZHANG, F.-F.; XU*, H.-J.; Org. Lett. 15 (2013) 7, 1472-1475, http://dx.doi.org/10.1021/ol400197y ; Sch. Med. Eng., Hefei Univ. Technol., Hefei 230009, Peop. Rep. China; Eng.) -H. Haber 32-049