内蒙古牙尔盖地区哈布楚浑迪隆起晚石炭世花岗岩类岩石化学特征及其构造环境

The petrochemical characteristics and tectonic environment of Late Carboniferous granitoids of the Habchuhudi’s uplift in Yalgai area, Inner Mongolia

通过对哈布楚浑迪隆起晚石炭世花岗岩类进行岩相学、年代学和岩石化学分析,首次系统讨论了牙尔盖地区与古生代区域构造线展布一致的古生代侵入岩岩石化学特征及构造环境。研究表明,该花岗岩类属于钙碱性系列,总体表现为高硅、中-高钾、偏铝质-过铝质特征。大离子亲石元素相对富集Rb,贫K、Ba,高场强元素相对富集Zr、Hf,Nb、Ta、Sr、P、Ti不同程度亏损。轻重稀土强烈分馏,轻稀土分馏明显,重稀土分馏不明显,Eu具有不同程度的亏损。LA-ICP-MS U-Pb测年结果显示206 Pb/238 U加权平均年龄为305.5±1.90 Ma,形成时代为晚石炭世。系列判别图解显示,研究区花岗岩类具有火山弧花岗岩特征,部分样品具有同碰撞或板内花岗岩特征,成因类型属S型。

The lithofacies,chronology and analysis of petrochemical characteristics and tectonic environment of the Paleozoic intrusive rocks for Habchuhudi’s uplift in Yalgai area was discussed systematically for the first time.The results show that the granites belong to calc-alkaline series and are characterized by high silicon,medium-high potassium and alumina-peraluminous.It’s also characterized by remarkable fractionation between LREEs and HREEs,especially obvious with LREEs and not with HREEs,and there are different negative Eu anomalies.LA-ICP-MS U-Pb dating results show that the weighted average age of 206Pb/238U is 305.5±1.90 Ma and the formation age was Late Carboniferous.Discriminant diagrams show that the granites in the study area(their genetic type is S-type)have the characteristics of volcanic arc granites,and some samples show the characteristics of syn-collision or intraplate granites.