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A multidisciplinary study of the emplacement mechanism of the Qingyang-Jiuhua massif in Southeast China and its tectonic bearings. Part Ⅱ: Amphibole geobarometry and gravity modeling

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。第二部分:闪石的大气压力和重力模拟

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摘要

The Late Mesozoic geology of the Lower Yangtze area is characterized by extensional sedimentary basins, numerous granitic plutons and several world-class ore deposits. Regionaly, the coeval tectonic and geo-dynamic framework remains inadequately investigated. In order to provide a more comprehensive understanding of the regional tectonic context, we performed a multidisciplinary study of the emplacement mechanism of the Qingyang-Jiuhua massif. It consists of the granodioritic Qingyang and the mon-zogranitic Jiuhua plutons, U-Pb dated at 142 ±1.0 Ma and 131 ±2.6 Ma, respectively. Biotite and amphibole cooling ages are 5-8 myr younger. Results deduced from field structural observation, petro-graphic and magnetic fabrics, paleomagnetism show that this massif was probably vertically emplaced by permissive intrusion coeval with weak regional extension. However, detailed information on the characteristics of this tectonic event and its emplacement depth was not documented. Therefore, we carried out an investigation of amphibole geobarometry and gravity modeling in order to address the emplacement mode of the plutons within their regional tectonic framework. Amphibole data show that the Qingyang-Jiuhua massif was emplaced in the upper crust at a depth between 5 and 12 km. Gravity modeling indicates that the massif is laccolithic. It is characterized by several NE-SW-striking linear thickening zones that we interpret as the feeder roots of the massif. These results led us to conclude that (1) the Qingyang-Jiuhua massif was fed by vertical, NE-SW striking tension gashes; (2) consequently the late Early Cretaceous tectonics in the study area was characterized by NW-SE extension.
机译:下扬子地区的晚中生代地质特征是伸展的沉积盆地,众多的花岗岩体和若干世界一流的矿床。就区域而言,中世纪构造和地球动力学框架仍未得到充分研究。为了更全面地了解区域构造背景,我们对庆阳-九华地块的进位机制进行了多学科研究。它由颗粒状的庆阳和单齿状的九华岩构成,U-Pb的年龄分别为142±1.0 Ma和131±2.6 Ma。黑云母和闪石的冷却年龄要小5-8迈。从现场结构观察,岩相图和磁性织物,古磁性学推论得出的结果表明,该地块可能是由允许侵入的同位带垂直侵入而形成的,区域扩展较弱。但是,有关该构造事件的特征及其进位深度的详细信息尚未记录。因此,我们进行了闪石几何气压和重力模型的研究,以解决小行星在其区域构造框架内的进位模式。闪石的数据表明,庆阳-九华地块位于上地壳中,深度为5至12 km。重力建模表明该地块是石质的。它的特点是有几个NE-SW引起的线性增厚带,我们将其解释为地块的馈电线根。这些结果使我们得出以下结论:(1)庆阳-九华地块受到NE-SW垂直垂直打击的拉力填隙作用; (2)因此,研究区的晚白垩世晚期构造以NW-SE扩展为特征。

著录项

  • 来源
    《Journal of Asian earth sciences》 |2014年第1期|94-105|共12页
  • 作者单位

    University of Chinese Academy of Sciences, Beijing 100049, China,Universite 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,SKL, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;

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

    Universite 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;

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

    Universite 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;

    Universite 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;

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

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

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

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    South China; Late Mesozoic extension; Al~(total) in amphibole geobarometry; Gravity modeling;

    机译:华南中生代晚期Al〜(总计)在闪石几何气压计中;重力建模;

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