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首页> 外文期刊>Journal of Asian earth sciences >A multidisciplinary study on the emplacement mechanism of the Qingyang-Jiuhua Massif in Southeast China and its tectonic bearings. Part Ⅰ: Structural geology, AMS and paleomagnetism
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A multidisciplinary study on the emplacement mechanism of the Qingyang-Jiuhua Massif in Southeast China and its tectonic bearings. Part Ⅰ: Structural geology, AMS and paleomagnetism

机译：中国东南部庆阳-九华地块的冲撞机制及其构造方位的多学科研究。第一部分：结构地质，AMS和古磁性

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摘要

During the Cretaceous, the South China Block (SCB) experienced a widely distributed extensional event including numerous plutons emplacement and basin opening. Investigations on the tectonic regime coeval with pluton emplacement, and emplacement mechanism of the pluton remain relatively rare in the SCB. In order to address these questions, a multidisciplinary approach, including field structural and pet-rographic observations, anisotropy magnetic susceptibility (AMS) and paleomagnetic analyses, was carried out on the Qingyang-Jiuhua granitic massif which intrudes into the Lower Yangtze fold belt in the northeastern part of the SCB. The Qingyang-Jiuhua massif is composed of the granodioritic Qingyang and monzogranitic Jiuhua plutons dated by zircon U-Pb method at ca. 142 Ma, and ca. 131 Ma, respectively. Our structural observations show that the intrusion of the Qingyang-Jiuhua massif does not modify the fold strike. A weak ductile deformation of the country rocks and granitoid can be only observed in the boundary zone with limited contact metamorphism. In the contact aureole of the massif, the foliation follows the pluton contour, and the mineral lineation is rare. When present, it exhibits a down-dip attitude. Field and microstructural observations indicate isotropic magmatic textures in most parts of the massif. The AMS analysis of 93 sites reveals weak values for the anisotropy degree (P_J ＜ 1.2) and oblate magnetic fabric dominance (T＞0) for most of the measured samples. Two principal foliation patterns are identified: horizontal foliations in the center of the plutons, and vertical foliations on the boundaries. Magnetic lineation strike is largely scattered, and weakly inclined at the scale of the entire massif. The paleomagnetic investigations indicate that (a) the younger Jiuhua pluton did not produce a remagnetiza-tion in the older Qingyang pluton, (b) no relative movement can be observed between these two plutons, (c) the entire massif did not experience any important relative movement with respect to South China, considering the paleomagnetic uncertainties. Integrating the newly obtained results with previous observations, our study favors a permissive emplacement mechanism for the two plutons, i.e. vertical magma intrusion into an opening space controlled by the NW-SE brittle stretching of the upper crust, which is in agreement with a weak extensional regional tectonic framework of the SCB.
机译：在白垩纪期间，华南地块（SCB）经历了广泛分布的伸展活动，包括大量的小行星侵入和盆地开放。在SCB中，与岩体位置有关的构造条件的调查以及岩体的沉积机理仍然相对较少。为了解决这些问题，对庆阳-九华花岗岩体进行了多学科研究，包括野外结构和岩石学观测，各向异性磁化率（AMS）和古磁分析，这些均侵入了长江下游的长江褶皱带。 SCB的东北部。庆阳-九华地块由锆石U-Pb法测年的粒状青阳和单生性九华岩体组成。约142 Ma，以及分别为131 Ma。我们的结构观察表明，庆阳-九华地块的侵入并没有改变褶皱走向。仅在接触变质作用有限的边界区域才能观察到乡村岩石和花岗岩的弱韧性变形。在地块的接触金针中，叶面遵循岩体轮廓，矿物纹路很少。当存在时，它表现出向下倾斜的态度。现场和微观结构观察表明，地块大部分地区各向同性的岩浆质地。 AMS对93个位点的分析显示，大多数测量样品的各向异性度（P_J ＜1.2）和扁磁织物优势（T＞ 0）均较弱。确定了两种主要的叶型模式：在云母中心的水平叶型和边界上的垂直叶型。磁线走向在很大程度上散布，并且在整个地块的尺度上微弱地倾斜。古地磁研究表明（a）较旧的九华岩体在较老的庆阳岩体中没有产生磁化作用;（b）在这两个岩体之间没有观察到相对运动;（c）整个地块没有经历任何重要的运动考虑古地磁不确定性，相对于华南的相对运动。将新获得的结果与以前的观测结果结合起来，我们的研究倾向于对两个云母的放位机制，即垂直岩浆侵入到由上地壳的NW-SE脆性拉伸控制的开口空间中，这与弱伸展性相符。 SCB的区域构造框架。

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  • 来源
    《Journal of Asian earth sciences》 |2014年第1期|76-93|共18页
  • 作者

    W. Wei; Y. Chen; M. Faure; Y.H. Shi; G. Martelet; Q.L. Hou; W. Lin; N. Le Breton; Q.C. Wang;

  • 作者单位

    University of Chinese Academy of Sciences, Beijing 100049, China,Univ d'Orleans, ISTO, UMR 7327, 45071 Orleans, France,CNRS/INSU, ISTO, UMR 7327, 45071 Orleans, France,BRGM, ISTO, UMR 7327, BP 36009, 45060 Orleans, France,Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;

    Univ d'Orleans, ISTO, UMR 7327, 45071 Orleans, France,CNRS/INSU, ISTO, UMR 7327, 45071 Orleans, France,BRGM, ISTO, UMR 7327, BP 36009, 45060 Orleans, France;

    Univ d'Orleans, ISTO, UMR 7327, 45071 Orleans, France,CNRS/INSU, ISTO, UMR 7327, 45071 Orleans, France,BRGM, ISTO, UMR 7327, BP 36009, 45060 Orleans, France;

    Hefei University of Technology, Hefei 230009, China;

    BRGM, ISTO, UMR 7327, BP 36009, 45060 Orleans, France;

    University of Chinese Academy of Sciences, Beijing 100049, China;

    Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;

    Univ d'Orleans, ISTO, UMR 7327, 45071 Orleans, France,CNRS/INSU, ISTO, UMR 7327, 45071 Orleans, France,BRGM, ISTO, UMR 7327, BP 36009, 45060 Orleans, France;

    Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;

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  • 正文语种 eng
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  • 关键词

    South China Block; Pluton emplacement mechanism; Anisotropy of magnetic susceptibility; Paleomagnetism; Cretaceous tectonic extension;

    机译：华南街区Pluton安置机制;磁化率各向异性;古磁性白垩纪构造扩展;

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