【作者】 仵康林；

【导师】 党犇；

【作者基本信息】 长安大学 ， 矿产普查与勘探， 2011， 硕士

【摘要】 阿拉善地区花岗岩类岩体广泛分布,目前对年代学研究及其成因和构造背景研究还很薄弱。本文运用锆石LA-ICP-MS U-Pb测年、采用荧光光谱方法分析和ICP-MS等分析方法对研究区内花岗岩类进行了同位素年代学研究和地球化学特征研究,结合前人认识和项目组的研究成果,对阿拉善地区华力西晚期花岗岩类的形成时代、岩石地球化学特征、岩石成因和大地构造背景方面进行了讨论。本文对宗乃山-沙拉扎山4个岩浆成因的花岗岩类样品测年,获得年龄分别为(273.3±3.9)Ma、(272.6±3.4)Ma、(273.5±4.2)Ma、(250.8±3.3)Ma,对牛泉山-巴彦诺尔公地区2个岩浆成因上的花岗岩类样品锆石测年得到(272.6±7.4)Ma、(272.0±9.0)Ma,均代表岩石的结晶年龄,这反映该区主要侵位时代分别为早二叠世末和晚二叠世末。岩石地球化学分析结果表明,两地区地球化学特征基本相似,显示南北两地华力西晚期花岗岩类在成因的相关性。其岩石类型主要以花岗岩、二长花岗岩和闪长岩类为主；SiO2含量为62.98～76.03%范围内,A/CNK显示样品属于准铝-过铝质岩石,属于钙碱性-高钾钙碱性系列,并普遍含有钾长石斑晶。在微量元素原始地幔标准化蜘蛛网图上,明显是Ba、Ta、Nb、Sr、Y、Tb负异常。在稀土元素配分曲线上,总体呈右倾,轻稀土相对富集,而重稀土相对亏损,个别样品表现出Eu的负异常。Sr负异常表明岩浆发生了明显的长石分离结晶。区内以Ⅰ型花岗岩为主,部分为A型花岗岩。高钾钙碱性Ⅰ型花岗岩(KCG)指示的是一种构造体制的变化,在本区指示了大陆会聚向离散的转折环境。综合研究表明,研究区早二叠世花岗质岩形成于由挤压向拉张的转变时期,是后碰撞的构造环境。更多还原

【Abstract】 Granitoids are widespread in Alashan block, and their genesis and tectonic setting have been an issue hot debate at the present time. LA-ICP-MS U-Pb zircon age and ICP-MS are reported for geochronology and geochemistry of the granitoids there,to reasearch combining previous understanding and group’s research results,then discuss geochemical characteristics and tectonic setting of middle-late Varisian period granitoids in Alashan block and have achieved some recognition.Zircon U-Pb dating of the six spotted magmatogenic diorite-granite from the region was performed, yielding the 273.3±3.9Ma,272.6±3.4Ma,273.5±4.2Ma,250.8±3.3Ma,272.6±7.4 Ma,272.0±9.0Ma, suggesting the Crystallization age and that invading in the Late Early Permain.geochemical characteristics show that the Zongnaihill-shalazhahill plutons and Niuquan bayannuoergong plutons geochemical basic similar. Geochemical characteristics indicate that main rock type is granitoid, monzonite and dioritoid, A/CNK present that the granite has metaluminous-rich potassium, with shoshonitic to Kcalc-alkaline and high-Kcalc-alkaline. In the trace element primitive mantle normalized spider diagrams, Ba, Ta, Nb, Sr, Y, Tb negative anomalies clearly display. The REE distribu- tion curves are of right inclinnation, which indicates LREE enrichment and the deficiency of HREE, very few sample display negative Eu anomalies...The granite is product of the tectonic transition from compression to introplate extension,it fromed in post-collisonal environment.更多还原