蚌埠隆起区东段五河群形成条件及时限研究

发布时间：2018-06-13 17:58

  本文选题：P-T评价 + 锆石定年　； 参考：《合肥工业大学》2016年硕士论文

【摘要】：蚌埠隆起区位于华北克拉通东南缘,是华北克拉通的重要组成部分,然而前人对于蚌埠隆起结晶基底形成的变质条件、时限以及构造环境的分析相对较为薄弱,对五河群形成的构造成因背景仍然存在争议,制约了人们全面理解该隆起的形成和演化过程。因此,本文在详细的野外地质调查基础上,以变质岩石学、同位素年代学以及岩石地球化学等为手段,对在蚌埠隆起东段朱顶-石门山地区出露的花岗片麻岩、糜棱岩化花岗片麻岩、黑云斜长片麻岩以及新发现的含石榴石花岗片麻岩进行了较为细致且综合的研究,并在此基础上,探讨了蚌埠隆起五河群形成的变质条件、构造环境以及演化过程,这对揭示华北克拉通东南缘蚌埠隆起东段的构造演化具有重要意义。通过对含石榴石花岗片麻岩样品进行电子探针矿物成分分析以及P-T条件估计,得出该样品的温压条件为736-788℃和0.76-0.89GPa,表明其形成于低压麻粒岩相条件。锆石LA-ICP-MS U-Pb定年分析记录了岩浆结晶事件和变质事件,它们对应的年龄分别为(2562±34)Ma～(2584±25)Ma、(2433±31)Ma至(2466±31)Ma和(2204±68.0)Ma。上述实验结果表明蚌埠隆起区东段具有与华北克拉通演化的一致性,即普遍经历了角闪岩相至麻粒岩相的变质环境以及多阶段的演化过程。对研究区花岗片麻岩进行的岩石地球化学研究结果表明：花岗片麻岩的原岩为岩浆岩,属正变质岩系列,岩石具有富钠、富钾的特点,为准铝质-弱过铝质岩,属钙碱性系列。该套花岗片麻岩明显富集Rb、Ba、K等大离子亲石元素(LILE),亏损Nb、Ta、Ti等高场强元素(HFSE),具有壳源岩浆的特征。结合锆石U-Pb定年结果,并通过岩石构造环境判别图解得出,花岗片麻岩的原岩为火山弧花岗岩,形成于岛弧构造环境。综合研究认为华北克拉通东南缘蚌埠隆起区花岗片麻岩的原岩主要形成于晚太古代岛弧环境,代表了该期板块俯冲—增生事件。
[Abstract]:The Bengbu uplift is located in the southeastern margin of the North China Craton and is an important part of the North China Craton. However, the metamorphic conditions, time limits and tectonic environment of the crystalline basement of the Bengbu uplift are relatively weak. The tectonic background of the Wuhe Group is still controversial, which restricts the overall understanding of the formation and evolution of the uplift. Therefore, on the basis of detailed field geological investigation, based on metamorphic petrology, isotopic chronology and geochemistry, the granitic gneiss exposed in the eastern section of Bengbu uplift, Zhuding-Shimenshan area, has been studied in this paper. Mylonitic granitic gneiss, black cloud plagioclase gneiss and newly discovered garnet granitic gneiss have been studied in detail and synthetically. On this basis, the metamorphic conditions of Wuhe Group in Bengbu uplift have been discussed. The tectonic environment and evolution process are of great significance to reveal the tectonic evolution of the eastern segment of Bengbu uplift in the southeastern margin of North China Craton. By means of electron probe mineral composition analysis and P-T condition estimation of garnet granitic gneiss samples, the temperature and pressure conditions of the samples are 736-788 鈩，

本文编号：2014912