蒋小洁, 刘松楠, 周丽云, 陈鑫, 王瑜. 0: 同构造岩浆流动与相对稳定环境下岩体侵位的差异性及其大地构造意义. 地质通报. DOI: 10.12097/gbc.2023.09.029
    引用本文: 蒋小洁, 刘松楠, 周丽云, 陈鑫, 王瑜. 0: 同构造岩浆流动与相对稳定环境下岩体侵位的差异性及其大地构造意义. 地质通报. DOI: 10.12097/gbc.2023.09.029
    Xiaojie JIANG, Songnan LIU, Liyun ZHOU, Xin CHEN, Yu WANG. 0: Difference of the syn-tectonic magma flow and granite emplacement in relatively stable tectonic environment and its tectonic implication. Geological Bulletin of China. DOI: 10.12097/gbc.2023.09.029
    Citation: Xiaojie JIANG, Songnan LIU, Liyun ZHOU, Xin CHEN, Yu WANG. 0: Difference of the syn-tectonic magma flow and granite emplacement in relatively stable tectonic environment and its tectonic implication. Geological Bulletin of China. DOI: 10.12097/gbc.2023.09.029

    同构造岩浆流动与相对稳定环境下岩体侵位的差异性及其大地构造意义

    Difference of the syn-tectonic magma flow and granite emplacement in relatively stable tectonic environment and its tectonic implication

    • 摘要: 花岗质岩浆岩是大陆地壳的重要组成部分,其岩浆作用和侵位过程是研究大陆形成与演化的重要依据。与相对稳定的构造环境下侵位的花岗岩不同,同构造岩浆流动通常发生在大陆边缘、造山带等构造活跃带,在强烈的构造应力场影响下,其岩体特征、侵位过程、流动方向通常十分复杂。华北板块北缘在晚古生代期间有大量花岗质岩体侵入,其构造属性与成因分析为研究古亚洲洋的俯冲与华北克拉通破坏提供关键证据。以华北板块北缘的大光顶岩体和盘山岩体为研究对象,进行从宏观到微观的构造变形以及岩石学特征分析,结合电子探针手段进行半定量的矿物学研究,并利用角闪石压力计来计算岩体形成的压力条件,从而反演侵位的深度。结果表明晚古生代(320-290Ma)的大光顶花岗闪长岩在露头尺度上表现为大量轴面低角度北倾的无根褶皱,显微镜下可见角闪石、黑云母等暗色矿物定向排列,包体和捕虏体长轴平行于流动面理,具有典型的同构造变形特征,其角闪石全铝压力计指示结晶压力为3.62~5.64 kbar,大致对应中地壳的深度(12.86~22.99km)。说明晚古生代华北板块北缘中下地壳重熔形成由北向南的同构造岩浆流动,形成大光顶岩体的同时也为中—深层次的应力传递提供媒介。而中生代盘山花岗岩中的包体、捕虏体未发生变形,也无暗色矿物定向排列,但岩体与围岩接触带发育热接触变质作用形成大理岩,属稳定构造环境下侵位的花岗岩。

       

      Abstract: Granitoid intrusions constitute most of continental crust, and provide vital evidences for researching continental formation and evolution. Different from granite emplacement in relatively stable tectonic environment, syn-tectonic magma flow usually occurs in active tectonic zones such as continental margin and orogenic belt. The structure of syn-tectonic granite, magmatic process and flow direction are usually complicated affected by strong tectonic stress field. A large number of granitic plutons intruded in the north margin of the North China Plate during the Late Paleozoic, and their tectonic properties and genetic analysis provide key evidence for the study of the subduction of the Paleo-Asian Ocean and the destruction of the North China Craton. The structural deformation and petrographic characteristics of the Daguangding granodiorite and Panshan granite on the northern margin of North China Plate are analyzed from macro to micro, and semi-quantitative mineralogy research is carried out by electron probe microanalysis. Forming pressure of the pluton are calculated by hornblende pressure gauge, so as to invert the emplacing depth. The results show that the late Paleozoic (320-290Ma) granodiorite is characterized by a large number of root-less folds with north dipping axial plane. Under the microscope, dark minerals such as amphiboles and biotite are oriented alignment, and the long axes of xenolith are parallel to the flow foliation, showing typical syn-tectonic deformation characteristics. Its hornblende all-aluminum manometer indicates a crystallization pressure of 3.62~5.64 kbar, roughly corresponding to the depth of the middle crust (12.86~22.99km). This indicates that the remelting of the middle and lower crust on the northern margin of the North China Plate in the late Paleozoic was formed by syn-tectonic magmatic flow from north to south, which formed the Daguangding pluton and also provided a medium for the stress transfer in the middle and deep layers. The xenolith in Mesozoic Panshan granite are not deformed, and there is no directional arrangement of dark minerals, but marble is formed by thermal contact metamorphism in the contact zone between pluton and surrounding rock, which belongs to granite emplacement under stable tectonic environment.

       

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