漠河盆地南缘塔木兰沟组火山岩锆石U-Pb定年、地球化学特征及其地质意义

ZIRCON U-Pb DATING AND GEOCHEMISTRY OF THE VOLCANIC ROCKS OF TAMULANGOU FORMATION IN THE SOUTH EDGE OF MOHE BASIN:Geological implication

对大兴安岭北段漠河盆地南缘的塔木兰沟组玄武安山岩进行锆石LA-ICP-MS U-Pb定年以及岩石地球化学研究,以便限定其形成时代以及火山活动和漠河断陷盆地演化之间的关系.测年结果显示该地区塔木兰沟组玄武安山岩的形成时代为129~147 Ma,为早白垩世早期.塔木兰沟组火山岩主要为高钾钙碱性火山岩系列,具有富集大离子亲石元素（LILE）和轻稀土元素（LREE）,亏损高场强元素（HFSE）的特征.岩浆源区为富集型地幔源区,上升过程中可能受上地壳物质混染.地球化学特征及构造背景显示,研究区塔木兰沟组火山岩形成于大陆板内拉张环境,与中生代漠河盆地断陷构造有关.

The paper studies the zircon LA-ICP-MS U-Pb dating and lithogeochemistry of the Mesozoic basaltic andesite of the Tamulangou Formation from the south edge of Mohe Basin in Northern Daxinganling to define its formation age and the relation between volcanic activities and the evolution of Mohe fault basin. The dating result shows that the age of the basaltic andesite ranges from 129 to 147 Ma, belonging to Early Cretaceous. The volcanic rocks of the Tamulangou Formation are mainly of high-K calc-alkaline series, with enrichment in large ion lithophile elements（LILEs）and light rare earth elements（LREE）and depletion in high field strength elements（HFSEs）. The magmatic source of the volcanic rocks was originated from partial melting of enriched mantle and probably contaminated by upper crustal materials during the ascending. The geochemical characteristics and tectonic background indicate that the volcanic rocks of the Tamulangou Formation was formed in a continental intraplate extensional environment, and related to the Mesozoic faulted structure of the Mohe Basin.