大兴安岭西缘玛尼吐组火山岩成因及构造指示

发布时间：2019-07-10 08:21

【摘要】：我国东北地区分布有大量中生代(侏罗纪至白垩纪)火山岩。选取大兴安岭西缘玛尼吐组粗安岩-粗面英安岩-流纹岩为研究对象,研究结果显示它们为高钾钙碱性的火山岩,主量、微量元素含量变化较大,SiO_2含量为56.71%~71.85%,Na_2O+K_2O含量为5.92%~10.18%,Na_2O/K_2O比值较高,为0.78~1.33,Mg~#为30.6~56.4。玛尼吐组火山岩的稀土元素配分图和微量元素蛛网图右倾明显,可见明显的Nb、Ta、Ti、Sr和Eu负异常(Nb~*=0.17~0.71,Sr~*=0.24~1.15,Eu~*=0.49~0.77)。稀土总量较高,为200×10~(-6)~949×10~(-6)。结果分析可知,玛尼吐组火山岩源岩与霍林河火山岩源岩相似,均为混合了少量先存古老地壳的新生基性下地壳。新生基性下地壳部分熔融形成安山质岩浆,并经角闪石+斜长石+钾长石+磷灰石+钛磁铁矿等的分离结晶形成了玛尼吐组粗安岩-粗面英安岩-流纹岩。玛尼吐组火山岩显著的岛弧地球化学特征说明其形成于与太平洋俯冲有关的岛弧环境。
[Abstract]:There are a large number of Mesozoic (Jurassic to Cretaceous) volcanic rocks in Northeast China. The trachyandesite-rhyolite of Manitu formation in the western margin of Daxing'an Mountains is selected as the research object. The results show that they are volcanic rocks with high potassium calc-alkaline content, the content of trace elements varies greatly, the content of SiO_2 is 56.71%, the content of Na _ 2O K _ 2O is 5.92% 10.18%, the ratio of Na _ 2O / K _ 2O is 0.78% 1.3, and the mg ~ (#) is 30.6% 56.4. The results show that they are volcanic rocks with high potassium calc-alkaline content, the content of trace elements varies greatly, the content of Na _ 2O K _ 2O is 5.92% 10.18%. The rare earth element distribution map and trace element cobweb diagram of volcanic rocks in Manitu formation are obviously tilted to the right, and obvious negative anomalies of Nb,Ta,Ti,Sr and Eu (Nb~*=0.17~0.71,Sr~*=0.24~1.15,Eu~*=0.49~0.77) can be seen. The total amount of rare earth is 200 脳 10 ~ (- 6) ~ 949 脳 10 ~ (- 6). The results show that the volcanic rocks of Manitu formation are similar to those of Huolinhe volcanic rocks, and all of them are new basic lower crust mixed with a small amount of pre-existing ancient crust. The granitic magma was formed by partial melting of the new basic lower crust, and the crude andesite-trachyandesite-rhyolite of the Manitou formation was formed by the separation and crystallization of hornblende plagioclase potassium feldspar apatite ilmenite and so on. The significant island arc geochemistry of volcanic rocks in Manitu formation indicates that it was formed in the island arc environment related to Pacific subduction.
【作者单位】：内蒙古自治区岩浆活动成矿与找矿重点实验室内蒙古自治区地质调查院;中国地质大学(武汉)地球科学学院;中山大学地球科学与工程学院;
【基金】：国家自然科学基金项目(41502210) 中国地质调查局“内蒙古新巴尔虎右旗地营子等六幅1∶5万地质矿产综合调查”子项目(12120115031301)
【分类号】：P542;P588.14

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