Abstract Neoproterozoic igneous rocks in the Jiangnan orogen can provide important information to unravel the tectonic evolution of the South China Block and are thus important for the reconstruction of Rodinia. Dacites and rhyolites in the Shangshu region, the eastern Jiangnan orogen, contain zircon grains with U-Pb ages of ca. 800 Ma. These felsic rocks have high Ga/Al ratios (2.3–3.7) and HFSE and HREE contents relative to the primitive mantle, thus resembling A-type granitoids. Dacites have negative zircon eHf(t) values (–2.8 to –18.7), indicative of derivation from primary magmas generated by partial melting of ancient continental crust. In contrast, rhyolites show positive eHf(t) values (+1.9 to +8.8) and are explained as derived from partial melting of juvenile lower mafic crust. Felsic volcanic rocks in Shangshu were formed in a post-orogenic extension setting shortly after the final amalgamation of the Yangtze and Cathaysia blocks at around 830 Ma. Combining our results with the previously published ones, we demonstrate that the 800 Ma extension-related magmatic activity was likely the earliest phase of the Neoproterozoic rifting in the South China Block. The tectonic transition from continental collision to a post-orogenic setting should have occurred after ca. 800 Ma.

中文翻译：

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碰撞后约 华南江南造山带东部800 Ma A型长英质火山岩

摘要 江南造山带新元古代火成岩可为揭示华南地块构造演化提供重要信息，对罗迪尼亚重建具有重要意义。江南造山带东部尚树地区英安岩和流纹岩含有锆石颗粒，U-Pb 年龄约为 . 800 马。这些长英质岩石相对于原始地幔具有高 Ga/Al 比 (2.3-3.7) 和 HFSE 和 HREE 含量，因此类似于 A 型花岗岩。英安岩的锆石 eHf(t) 值为负（–2.8 至 –18.7），表明源自古代大陆地壳部分熔融产生的原生岩浆。相比之下，流纹岩显示出正 eHf(t) 值（+1.9 至 +8.8），并被解释为源自幼年下基性地壳的部分熔融。上树长英质火山岩形成于约 830 Ma 的扬子地块和华夏地块最终合并后不久的造山后伸展环境。结合我们之前发表的结果，我们证明 800 Ma 与伸展相关的岩浆活动可能是华南地块新元古代裂谷的最早阶段。从大陆碰撞到造山后环境的构造转变应该发生在大约 10 年之后。800 马。从大陆碰撞到造山后环境的构造转变应该发生在大约 10 年之后。800 马。从大陆碰撞到造山后环境的构造转变应该发生在大约 10 年之后。800 马。