阿尔金且末—若羌地区新元古代花岗质岩石成因及其对Rodinia超大陆汇聚时限的约束

    Petrogenesis for Neoproterozoic granitic rocks in Altyn Qiemo-Ruoqiang area, and implications for determining the timing of Rodinia supercontinent's convergence

    • 摘要: 阿尔金造山带广泛发育新元古代花岗质岩浆岩,形成年龄为800~1000 Ma,可能是Rodinia超大陆汇聚阶段的产物,因此新元古代花岗质岩浆的研究对探讨阿尔金造山带的演化过程具有重要意义。选取南阿尔金地块且末—若羌地区的花岗质岩石为研究对象,开展了详细的岩石学、岩石地球化学及地质年代学研究。结果表明:①且末—若羌地区3类花岗质岩石的轻稀土元素相对于重稀土元素富集,显示右倾配分模式,具明显的负Eu异常(δEu=0.14~0.6),富集Th、U、K等大离子亲石元素,亏损Ba、Ti、Nb、Ta、Sr等高场强元素;②锆石U-Pb年龄为899~915 Ma。综合区域地质演化历史表明,且末—若羌地区3类花岗质岩石形成于同碰撞构造环境,是Rodinia超大陆汇聚阶段板块之间俯冲、碰撞的产物。

       

      Abstract: The Neoproterozoic granitic magma activity was widespread in the Altyn orogenic belt, with formation ages around 800~1000 Ma.These magmatic events are thought to be associated with the convergence of the Rodinia supercontinent.Therefore, the study of Neoproterozoic granitic magma is of great significance for gaining insights into the evolution processes of the Altyn orogenic belt.In this study, we present precise results from petrological, geochronological and geochemical investigations of the granitic rocks from the Qiemo-Ruoqiang area in the southern Altyn block.Our findings indicate that: ①In comparison to the enrichment of light rare earth elements(LREE), heavy rare earth elements(HREE)exhibit a pronounced right-leaning characteristic, accompanied by a distinct negative Eu anomaly(δEu=0.14~0.6).These rocks are enriched in large ion lithophile elements like Th, U, and K, while simultaneously showing depletion in high field strength elements such as Ba, Ti, Nb, Ta, and Sr.②Zircon U-Pb ages fall within the range of approximately 899 Ma to 915 Ma.Comprehensive studies have shown that the three categories of granitic rocks in the Qimo-Ruoqiang region were formed in a syn-collision tectonic environment, which were the products of subduction and collision between plates during the convergence stage of the Rodinia supercontinent.

       

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