内蒙古柴河地区柴青岩体年代学及地球化学特征

Chronology and geochemistry features of Chaiqing pluton in Chaihe area, Inner Mongolia

内蒙古柴河地区位于大兴安岭中部,对研究区内柴青岩体进行了系统的岩相学、锆石U-Pb同位素年代学和地球化学分析。研究表明柴青岩体主体岩性为花岗斑岩,LA-ICP-MS锆石U-Pb测年年龄为（139.1±2.7）Ma,即早白垩世。岩石富硅（Si O2=72.15%-72.43%）、铝（Al2O3=14.21%-14.36%）、碱（K2O＋Na2O=8.77%-8.84%）,贫铁（FeO＊=2.02%-2.04%）、镁（Mg O=0.6%-0.62%）、钙（Ca O=0.72%-1.21%）,为高钾钙碱性系列岩石。样品相对富集轻稀土亏损重稀土,具有Eu异常（δEu=0.52）,富集Ba、K、Cs、Th、U,亏损Nb、P、Ti,为I型花岗斑岩。柴青岩体具有造山后花岗斑岩的特征,形成于早白垩世伸展的构造背景。

The Chaihe area of Inner Mongolia is located in the central Greater Xingan Range. We systematically studied the petrography, zircon U-Pb isotope chronology and geochemistry of Chaiqing pluton. The study shows that Chaiqing pluton is mainly of granite-porphyry, the LA-ICP-MS U-Pb dating in zircon is 139.1±2.7Ma, suggest it was intruded in the Early Cretaceous. The granite-porphyry is high in Si O2（72.15-72.43%）, Al2O3（14.21-14.36%） and alkali（K2O＋Na2O=8.77-8.84%）, besides it＇s low in Fe O＊（2.02-2.04%）, Mg O（0.6-0.62%） and Ca O（0.72-1.21%）. Indicates it＇s High-K Calc-alkaline Serise. The samples are enrichment of LREEs relative to HREEs, have negative Eu anomalies（δEu=0.52）, enriched in Ba, K, Cs, Th, U and depleted in Nb, P, Ti. Shows it＇s I-type granite-porphyry. Chaiqing pluton has the characteristic of post-orogenic granite-porphyry and intruded in extensional environment in the Early Cretaceous.