Abstract The South China Craton consists of the Yangtze and Cathaysia blocks that were welded together along the Jiangnan Fold Belt in the Neoproterozoic. The Neoproterozoic magmatism in the western and northern margins of the Yangtze Block is characterized by voluminous volcano-sedimentary strata, numerous felsic intrusions and many mafic-ultramafic plutons which provide a good opportunity to examine the geodynamics and tectonic evolution of the South China Craton during the assembly and breakup of Rodinia. Based on the geochronological and geochemical data, our study shows that the Neoproterozoic igneous rocks in the western and northern margins of the Yangtze Block were formed in subduction- and rift-related tectonic settings, respectively. In the western margin of the Yangtze Block, the Neoproterozoic mafic and ultramafic rocks show arc-affinity trace elemental compositions that are indicative of mantle sources enriched by slab fluids. High-δ18O mafic rocks (850–780 Ma) were derived from mantle wedges that were modified by sediment melts, whereas low-δ18O mafic rocks (750–740 Ma) were formed by partial melting of mantle sources further enriched by altered oceanic crust melts. The widespread calc-alkaline I-type granitoids in this region, generated between 870 and 750 Ma, show negative to positive whole rock eNd (−4.9 to +4.8) and variable zircon eHf values (−1.9 to +10.6), similar to those of the contemporary mafic-ultramafic rocks, suggesting that they were produced by melting of the juvenile crust. The 780–750 Ma adakitic granitoids are characterized by high Sr/Y (19–318) and low Y (1.78–17.9 ppm) and have relatively constant eNd (−2.1 to +2.9) and eHf (+4.3 to +7.1) and mantle-like δ18O values (3.40‰ to 6.86‰), suggesting that they were partial melts of a subducted oceanic slab. These three types of igneous rocks demonstrate that the Neoproterozoic magmatism in the western margin of the Yangtze Block was controlled by a continuous subduction system. However, Neoproterozoic magmatism in the South Qinling Belt at the northern margin of the Yangtze Block generated both arc- and rift-related igneous rocks. The arc-like mafic-ultramafic rocks are thought to have been derived from a subduction-modified lithospheric mantle source, whereas the MORB-affinity mafic rocks were probably sourced from an asthenosphere mantle. Associated Neoproterozoic granitoids were produced by melting of the juvenile mafic crust, except minor felsic rocks derived from the ancient basement. Widespread 800–700 Ma volcano-sedimentary sequences and 650 Ma mafic dike swarms suggest an extensional environment. Neoproterozoic magmatic zircons from felsic volcanic rocks and HP/UHP metamorphic rocks preserve low-δ18O values that were inherited from their protolith which underwent high temperature hydrothermal interaction in a rift setting. On the basis of these observations, the Neoproterozoic magmatism in the South Qinling Belt is proposed to have been controlled by a subduction-transform edge propagator (STEP) in relation to the continuous subduction system at the western margin of the Yangtze Block.

中文翻译：

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受板片俯冲和俯冲-转换-边缘-传播控制的扬子地块（华南）西、北缘新元古代岩浆活动

摘要 华南克拉通由新元古代沿江南褶皱带焊接在一起的扬子和华夏地块组成。扬子地块西、北缘新元古代岩浆活动以火山沉积地层大、长英质侵入体众多、基性-超铁质岩体为特征，为研究华南克拉通的地球动力学和构造演化提供了良好的契机。罗迪尼亚的组装和解体。根据年代学和地球化学资料，我们的研究表明，扬子地块西缘和北缘的新元古代火成岩分别形成于俯冲和裂谷相关的构造环境中。在扬子地块西缘，新元古代基性和超基性岩石显示出弧亲和微量元素组成，表明地幔源富含板片流体。高δ18O基性岩（850-780 Ma）来源于沉积物熔体改性的地幔楔，而低δ18O基性岩（750-740 Ma）是由地幔源部分熔融形成的，被改变的洋壳熔体进一步富集. 该地区广泛分布的钙碱性 I 型花岗岩，在 870 到 750 Ma 之间生成，显示出从负到正的整岩 eNd（-4.9 到 +4.8）和可变的锆石 eHf 值（-1.9 到 +10.6），与那些相似现代镁铁质-超镁铁质岩石，表明它们是由幼年地壳熔化产生的。780-750 Ma 埃达克质花岗岩的特征是高 Sr/Y (19-318) 和低 Y (1.78-17. 9 ppm）并且具有相对恒定的 eNd（-2.1 至 +2.9）和 eHf（+4.3 至 +7.1）和类似地幔的 δ18O 值（3.40‰ 至 6.86‰），表明它们是俯冲大洋板块的部分熔体。这三种火成岩表明扬子地块西缘新元古代岩浆活动受连续俯冲系统控制。然而，扬子地块北缘南秦岭带的新元古代岩浆作用产生了弧形和裂谷相关的火成岩。弧状镁铁质-超镁铁质岩石被认为来自俯冲改造的岩石圈地幔源，而MORB亲和基性岩石可能来自软流圈地幔。伴生的新元古代花岗岩是由幼年基性地壳熔融产生的，除了来自古代地下室的少量长英质岩石。广泛分布的 800-700 Ma 火山沉积序列和 650 Ma 基性岩脉群表明存在伸展环境。来自长英质火山岩和 HP/UHP 变质岩的新元古代岩浆锆石保留了低 δ18O 值，这些值是从它们的原岩继承的，这些原岩在裂谷环境中经历了高温热液相互作用。在这些观测的基础上，提出南秦岭带新元古代岩浆活动受扬子地块西缘连续俯冲系统的俯冲转换边缘传播器（STEP）控制。来自长英质火山岩和 HP/UHP 变质岩的新元古代岩浆锆石保留了低 δ18O 值，这些值是从它们的原岩继承的，这些原岩在裂谷环境中经历了高温热液相互作用。在这些观测的基础上，提出南秦岭带新元古代岩浆活动受扬子地块西缘连续俯冲系统的俯冲转换边缘传播器（STEP）控制。来自长英质火山岩和 HP/UHP 变质岩的新元古代岩浆锆石保留了低 δ18O 值，这些值是从它们的原岩继承的，这些原岩在裂谷环境中经历了高温热液相互作用。在这些观测的基础上，提出南秦岭带新元古代岩浆活动受扬子地块西缘连续俯冲系统的俯冲转换边缘传播器（STEP）控制。