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    闽东沿海构造窗晚古生代岩浆岩LA-ICP-MS锆石U-Pb年龄及其地质意义

    LA-ICP-MS zircon U-Pb ages of the Late Paleozoic magmatic rocks in the tectonic window along the eastern coastal Fujian Province and their geologic significance

    • 摘要: 闽东沿海构造窗位于华夏地块东缘,其内部蕴含并发育着极为复杂的变质基底,为探究前中生代的构造演化提供了关键线索。文章以福建省周宁吾凤楼构造窗和屏南黛溪构造窗内的岩浆岩作为研究对象,采用LA-ICP-MS锆石U-Pb定年技术对岩浆岩展开深入分析,并进一步探讨了这些岩浆岩的成因及其地质意义。锆石U-Pb定年结果表明,该区岩浆岩形成于晚石炭世(316~335 Ma),且岩浆岩中存在年龄为 843~2384 Ma 的继承锆石,说明构造窗内的岩浆事件发生在晚古生代,这些岩浆岩可能是元古代(变)沉积岩发生部分熔融后形成的。综合前人研究成果及岩相古地理分析结果,认为东南沿海地区晚古生代岩浆岩形成于陆内造山之后的伸展构造背景之下,研究区在晚古生代可能经历了从挤压造山阶段到板内伸展阶段的构造转变,而这种构造转变与陆内造山机制密切相关。该研究结果将有助于进一步深化对闽东沿海地区地质构造演化历史的认识。

       

      Abstract: The coastal tectonic window of eastern Fujian is located on the eastern edge of the Cathaysia Block and contains a complex metamorphic basement, which provides key clues for exploring the tectonic evolution of the Pre-Mesozoic. This paper focuses on the magmatic rocks in the Wufenglou and Daixi tectonic windows in Zhouning, Fujian Province, and applies LA-ICP-MS zircon U-Pb dating to further explore the petrogenesis and geological significance. The dating results show that the magmatic rocks formed in the Late Carboniferous (316-335 Ma) and contain inherited zircons of 843-2 384 Ma. Thus it can be determined that the magmatic event in the tectonic window occurred in the Late Paleozoic, and the magmatic rocks perhaps sourced from partial melting of Proterozoic sedimentary rocks(variable). Combining with the previous research and the analysis of lithofacies paleogeographic changes, it is believed that the Late Paleozoic magmatic rocks along the southeast coast formed in the extensional tectonic setting after intracontinental orogenesis, and the region may has undergone a tectonic transition from extrusion orogeny to intracontinental extension in the Late Paleozoic, which is closely related to the intracontinental orogenesis mechanism. The research results contribute to a deeper understanding on regional geological evolution and provide new perspectives and data support for related research.

       

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