大兴安岭北段奇力滨地区玛尼吐组火山岩年代学、地球化学特征及其构造意义  

Geochronology and geochemical characteristics of volcanic rocks from the Manitu Formation in the Qilibin area,northern Great Xing’an Range and its geological significance

作　　者：崔玉斌 王凯 何付兵[1] 尹刚伟 王召林[3] 王广磊 折士焜 CUI Yubin;WANG Kai;HE Fubing;YIN Gangwei;WANG Zhaolin;WANG Guanglei;SHE Shikun(Beijing Institute of Geological Survey,Beijing 100195,China;Hebei Geological Worker's University,Shijiazhuang,Hebei 050081,China;China Deep Ex ploration Center-SinoProbe Center,China Geological Survey&Chinese Academy of Geological Sciences,Beijing 100037,China;China Non Ferrous Metals Resource Geological Survey,Beijing 100012,China)

机构地区：[1]北京市地质调查研究院,北京100195 [2]河北地质职工大学,河北石家庄050081 [3]中国地质科学院地球深部探测中心,北京100037 [4]有色金属矿产地质调查中心,北京100012

出　　处：《地质学报》2021年第11期3301-3316,共16页Acta Geologica Sinica

基　　金：中国地质调查局内蒙古鄂伦春自治旗奇力滨地区地质矿产调查项目(编号12120115031001)成果;北京市市级职工创新工作室(城市地质、活动构造与监测)联合资助的成果。

摘　　要：大兴安岭北段奇力滨地区玛尼吐组火山岩主要为粗面安山岩和粗面岩。LA-ICP-MS锆石U-Pb年龄为142.2~141 Ma,表明火山岩形成于早白垩世。岩石地球化学结果表明,奇力滨地区玛尼吐组火山岩SiO_(2)含量介于54.09%~64.89%之间,具有高铝Al;O_(2)(14.67%~17.27%)、高全碱K_(2)O+Na_(2)O(6.33%~8.74%),较低的MgO(0.81%~2.71%)和Mg;(24.84~46.15),为高钾钙碱性火山岩;稀土总量(∑REE)介于146.51×10^(-6)~193.29×10^(-6)之间,轻重稀土分馏明显(La/Yb)_(N)=8.5~15.52,弱的负铀异常(δEu=0.64~0.96);微量元素以富集Rb、Ba、K等大离子亲石元素(LILE)和轻稀土元素(LREE),亏损Ta、Nb、Ti、Zr、P等高场强元素(HFSE)为特征,同时具有Hf正异常和高Th/Ta、Th/Nb比值,较低的Lu/Yb(0.14~0.16)和Rb/Sr(0.02~0.17)比值。结合前人研究成果,本研究认为奇力滨地区玛尼吐组火山岩岩浆源区为俯冲消减板片流体交代的地幔楔部分熔融,在岩浆上升过程中经历了分离结晶作用和浅部地壳物质的同化混染。该区火山岩形成与蒙古-鄂霍茨克洋闭合造山后的岩石圈伸展和软流圈上隆作用有关。The volcanic rocks in the Manitu Formation from the Qilibin area,northern Great Xing’an Range are mainly composed of trachyandesite and trachyte.Zircon U-Pb dating results show that they formed during the Early Cretaceous with an age of 142.2~141 Ma.The geochemical characteristics indicate that the volcanic rocks in the Manitu Formation from the Qilibin area are high in SiO_(2)(54.09%~64.89%),Al;O_(2)(14.67%~17.27%)and low in MgO(0.81%~2.71%),total alkaline K_(2)O+Na_(2)O(6.33%~8.74%),and Mg;(24.84~46.15),belonging to the calc-alkaline series with high K contents.The rare earth elements analysis show that the total rare earth elements(∑REE)are in the range of 146.51×10^(-6)~193.29×10^(-6)with insignificant negative Eu anomalies(δEu=0.64~0.96),and intense fractionation between LREE and HREE((La/Yb)_(N)=8.5~15.52).The trace elements are characterized by LILE(e.g.,Rb,Ba,K)and LREE enrichment and HFSE(e.g.,Ta,Nb,Ti,Zr,P)depletion,and containpositive Hf anomalies,high ratios of Th/Ta,Th/Nb,low ratios of Lu/Yb(0.14~0.16)and Rb/Sr(0.02~0.17).Combining their geochemical characteristics with previous studies of this area,the magma for the volcanic rocks in the Manitu Formation from the Qilibin area was derived from the partial melting of the subduction fluid metasomatized mantle wedge,and experienced fractional crystallization and contaminations of crust during the magma ascent.It is possible that these volcanic rocks in the Qilibin area were formed by the collision-postorogenic extension of the Mongolia-Okhotsc Ocean and the upwelling of asthenosphere.

关 键 词：锆石U-PB年龄 地球化学 玛尼吐组 大兴安岭北段 奇力滨地区 

分 类 号：P588.14[天文地球—岩石学] P548[天文地球—地质学]