大兴安岭中段哈达陶勒盖组火山岩U-Pb定年及成因

为了研究大兴安岭中段哈达陶勒盖组火山岩的形成时代和岩石成因，进行了锆石U-Pb同位素年龄测试和地球化学研究.LA-ICP-MS锆石U-Pb定年结果显示，哈达陶勒盖组火山岩形成于234~244Ma的中三叠世.岩石地球化学研究表明，哈达陶勒盖组火山岩具有低硅富碱、富钙镁的特征;稀土丰度总量w(∑RE)= 122.32×10^-6~140.66×10^-6，轻、重稀土分馏较明显，m(La)/m (Yb)_N=11.99~18.68， 无明显Eu负异常(δ_○Eu=0.84~0.98)，微量元素以富集Rb，K，Ba，Th，亏损Nb，P，Ti为特征.哈达陶勒盖组火山岩岩浆源区为富集的岩石圈地幔， 并遭受了地壳物质的混染.

Zircon U-Pb Dating and Petrogenesis of Volcanic Rocks in Hadataolegai Formation， Middle Great Xing’an Range

Zircon U-Pb isotopic dating and geochemical analysis were used to study the formation age and petrogenesis of the volcanic rocks in Hadataolegai Formation， the middle Great Xing’an Range. LA-ICP-MS dating results show that the volcanic rocks in Hadataolegai Formation formed in Middle Triassic from 234Ma to 244Ma. The geochemical study suggests that the volcanic rocks are poor in silicon，rich in alkalis， calcium and magnesium. The total RE amount ranges from 122.32×10^-6 to 140.66×10^-6. Fractionation of LRE and HRE is obvious［m(La)/m(Yb)_N=11.99~18.68］ and Eu has no anomalies (δ_Eu=0.84~0.98). The trace element geochemistry are characterized evidently by enrichment of Rb， K， Ba， Th， and depletion of Nb， P， Ti. Original magma of the volcanic in Hadataolegai Formation is chiefly derived from enriched lithospheric mantle， and contaminated by crustal material.