宋维民, 杜继宇, 那福超, 庞雪娇, 杨佳林, 刘英才, 孙巍, 陶楠, 葛锦涛. 大兴安岭中段突泉地区早白垩世碱性流纹岩锆石U-Pb定年及岩石成因[J]. 地质通报, 2019, 38(4): 619-631.
    引用本文: 宋维民, 杜继宇, 那福超, 庞雪娇, 杨佳林, 刘英才, 孙巍, 陶楠, 葛锦涛. 大兴安岭中段突泉地区早白垩世碱性流纹岩锆石U-Pb定年及岩石成因[J]. 地质通报, 2019, 38(4): 619-631.
    SONG Weimin, DU Jiyu, NA Fuchao, PANG Xuejiao, YANG Jialin, LIU Yingcai, SUN Wei, TAO Nan, GE Jintao. Zircon U-Pb dating and petrogenesis of Early Cretaceous alkaline rhyolites in Tuquan Basin of middle Da Hinggan Mountains[J]. Geological Bulletin of China, 2019, 38(4): 619-631.
    Citation: SONG Weimin, DU Jiyu, NA Fuchao, PANG Xuejiao, YANG Jialin, LIU Yingcai, SUN Wei, TAO Nan, GE Jintao. Zircon U-Pb dating and petrogenesis of Early Cretaceous alkaline rhyolites in Tuquan Basin of middle Da Hinggan Mountains[J]. Geological Bulletin of China, 2019, 38(4): 619-631.

    大兴安岭中段突泉地区早白垩世碱性流纹岩锆石U-Pb定年及岩石成因

    Zircon U-Pb dating and petrogenesis of Early Cretaceous alkaline rhyolites in Tuquan Basin of middle Da Hinggan Mountains

    • 摘要: LA-ICP-MS锆石U-Pb年龄表明,突泉地区碱性流纹岩锆石的206Pb/238U年龄分别为135±1Ma、133±1Ma,属于早白垩世岩浆活动的产物。岩石地球化学资料表明,碱性流纹岩具富SiO2、K2O和高TFeO/MgO值,低Al2O3、CaO和MgO的特征,属于高钾钙碱性系列岩石,稀土元素总量较高,轻、重稀土元素分馏明显,具右倾的稀土元素分布模式,负Eu异常明显,相对富集Rb、U、Zr、Hf,亏损Sr、Ti、Nb、Ta等元素,花岗岩判别图解上,样品分布在A型花岗岩区;在Nb-Y-3Ga图解上,显示拉张构造环境的A2型花岗岩的特征;元素地球化学示踪指出,突泉地区碱性流纹岩可能起源于下地壳的部分熔融,结合区域上分布的同时代火山岩及A型花岗岩类,可以限定碱性流纹岩形成于伸展构造背景,并可能与北部蒙古-鄂霍茨克缝合带的演化有关。锆石Hf同位素研究显示,本区早白垩世流纹岩εHft)值为+4.2~+10.7,其二阶模式年龄平均为0.74~0.76Ga,结合松嫩地块、兴安地块Hf同位素资料,表明兴安地块与松嫩地块具有相似的地壳增生过程。

       

      Abstract: The LA-ICP-MS zircon 206Pb/238U age estimates for the alkeline rhyolites yielded weighted average ages of 135±1Ma and 133±1Ma, indicating Early Cretaceous. The whole-rock geochemistry of the alkeline rhyolites shows an A-type magmatic affinity, with a typical enrichment of SiO2, K2O and a high ratio of TFeO/MgO, and low content of Al2O3, CaO and MgO, belonging to Khigh calc-alkaline series rocks; high ∑REE and fractionated REE patterns show strong negative Eu anomalies, relative enrichment of Rb, U, Zr, Hf, but depletion of Sr, Ti, Nb, Ta. In the discrimination diagrams of granites, all of the samples show the characteristics of A-type granites; in the Nb-Y-3Ga diagram, the samples show the characteristics of A2-type granites. These elements show that the alkeline rhyolites were derived from partial melting of crust materials. Viewed from regional correlations with the volcanic rocks as well as A-type granites, it is held that the alkeline rhyolites were associated with an extensional tectonic setting, being the product of a regional extensional environment associated with the evolution of Mongol-Khotsk suture. Zircon Hf isotope analyses show that dacite of Cretaceous have εHf(t) values of +4.2~+10.7 with Hf modal ages being 0.74~0.76Ga, indicating that there existed similar crustal processes between Xing'an block and Songnen block.

       

    /

    返回文章
    返回