内蒙古乌兰乌台花岗闪长岩U-Pb年龄、地球化学特征及地质意义  

Zircon U-Pb Age and Geochemical Characteristics of the Granodiorite in Wulanwutai,Inner Mongolia and Its Geological Significance

作　　者：程天赦[1] 杨文静[1] 张学斌[1] 吴荣泽[1] 周长红[1] CHENG Tianshe;YANG Wenjing;ZHANG Xuebin;WU Rongze;ZHOU Changhong(Tianjin Institute of Geological Survey,Tianjin300191,China)

机构地区：[1]天津市地质调查研究院,天津300191

出　　处：《现代地质》2021年第5期1231-1239,共9页Geoscience

基　　金：中国地质调查局项目“1:50000扎布其尔沃布勒吉幅、杰林牧场幅、白音诺尔农场幅、巴拉嘎尔牧场牧业小组幅、毛登牧场第二生产队幅区域地质调查”(中国地质调查局基[2010]矿评01-19-01)

摘　　要：内蒙古乌兰乌台花岗闪长岩位于兴蒙造山系内蒙古中部弧盆系锡林浩特岩浆弧中段。为探讨其成因类型和构造背景,开展了150000区域地质调查工作,对其进行了年代学、岩石矿物学及岩石地球化学研究。结果表明,花岗闪长岩的LA-ICP-MS锆石U-Pb谐和年龄为(384.8±5.1)Ma,形成于晚泥盆世。主要矿物为斜长石、钾长石、石英、黑云母及角闪石,副矿物组合属锆石-钛铁矿-磷灰石型,此外还含少量独居石、磁铁矿,其矿物特征与Barbarin花岗岩分类中CPG(含堇青石过铝质花岗岩类)较相近。另外,乌兰乌台花岗闪长岩富钾(K_(2)O含量为3.10%~3.94%),富铝(Al_(2)O_(3)为11.70%~12.89%),属过铝质岩石,其A/CNK=1.16~1.25,含黑云母,副矿物中含有磷灰石、独居石、钛铁矿,岩体见闪长岩包体,指示乌兰乌台花岗闪长岩可能来源于壳-幔混源岩浆,与西伯利亚板块同华北板块陆-陆碰撞有关。The Wulanwutai granodiorite in Inner Mongolia is located in the middle part of Xilinhot magmatic arc of an arc-basin system, in the middle part of Xingmeng orogen. To discuss its genetic type and tectonic background, 1∶50,000 regional geological survey was conducted and the petrology, mineralogy, geochronology and petrochemistry of the granodiorite were studied. The LA-ICP-MS zircon U-Pb age of(384.8±5.1) Ma indicates a Late Devonian granodiorite emplacement. The rocks mainly contain plagioclase, K-feldspar, quartz, biotite, and amphibole, with accessory zircon, ilmenite, apatite, monazite, and magnetite. The mineral contents resemble typical CPG(cordierite-bearing peraluminous granites) in Barbarin granite classification. In addition, the granodiorite is rich in K_(2)O(3.10%-3.94%) and Al_(2)O_(3)(11.70%-12.89%), and is peraluminous(A/CNK=1.16-1.25). The rocks also contain diorite xenolith. Hence, it is considered that the primary magma of the granodiorite may have derived from partial melting of a crust-mantle mixed source, and formed during the continent-continent collision between the Siberian and North China plates.

关 键 词：兴蒙造山带 花岗闪长岩 U-PB定年 晚泥盆世 陆-陆碰撞 

分 类 号：P588.1[天文地球—岩石学] P597[天文地球—地质学]