四川地质学报

作为前寒武Rodinia超大陆的一部分，扬子陆块在新元古代时期的构造岩浆演化是了解Rodinia超大陆裂解机制的重要一环。本文对陕西南部凤凰山花岗闪长岩样品进行了镜下岩相学观察、微量元素含量分析，以及原位微区锆石U-Pb定年工作。该花岗闪长岩具有过铝质、弱碱性的特征，是典型的S型花岗岩，其源区可能以富集斜长石的碎屑沉积物为主；侵位时代在～760Ma的新元古代。结合邻区内～820Ma的构造演化，岩浆活动被认为是地幔柱撞击导致的Rodinia超大陆裂解的响应。745～760 Ma的岩浆活动可以视为超大陆裂解末期的反映，因此，凤凰山花岗闪长岩指示了扬子陆块新元古代时期伸展裂解的大地构造背景。

As a part of the Precambrian Rodinia supercontinent, the tectonic magmatic evolution of the Yangtze Block in the Neoproterozoic period is an important link in understanding the rifting mechanism of the Rodinia supercontinent. This paper conducts a detailed field geological investigation, microscopic petrographic observation, analysis of the contents of major and trace elements in the whole rock, as well as in-situ micro-area zircon U-Pb dating of granodiorite samples from Fenghuang Mountain in southern Shaanxi. The granodiorite has the characteristics of peraluminous and weakly alkaline.It is a typical S-type granite, and its source area may be mainly composed of clastic deposits enriched with plagioclase. The Formation Age is in the Neoproterozoic at ～760Ma. Combined with the tectonic evolution of ～820Ma in the adjacent area, magmatic activity is considered a response to the rifting of the Rodinia supercontinent caused by mantle plume impacts. Therefore, the granodiorite of Fenghuang Mountain indicates the tectonic background of the extensional rifting of the Yangtze Block during the Neoproterozoic.