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内蒙古乌拉特中旗克布镁铁质-超镁铁质岩体年代学、矿物学和岩石地球化学
投稿时间:2016-05-23  修订日期:2017-07-05  点此下载全文
引用本文:党智财,李俊建,付超,唐文龙,刘跃,赵泽霖,吴兴源,孙宏伟.2018.内蒙古乌拉特中旗克布镁铁质-超镁铁质岩体年代学、矿物学和岩石地球化学[J].地质学报,92(2):278-297
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作者单位E-mail
党智财 1) 中国地质调查局天津地质调查中心天津300170 dangzhicai@163.com 
李俊建 1) 中国地质调查局天津地质调查中心天津300170 junjianl@163.com 
付超 1) 中国地质调查局天津地质调查中心天津300170  
唐文龙 1) 中国地质调查局天津地质调查中心天津300170  
刘跃 3) 中国地质大学地质过程与矿产资源国家重点实验室北京100083  
赵泽霖 1) 中国地质调查局天津地质调查中心天津300170 2) 中国地质科学院研究生部北京100037  
吴兴源 1) 中国地质调查局天津地质调查中心天津300170  
孙宏伟 1) 中国地质调查局天津地质调查中心天津300170  
基金项目:国家科技攻关计划
中文摘要:内蒙古乌拉特中旗地处华北陆块北缘西段,大地构造分区属于狼山-白云鄂博陆缘裂谷。区域上,镁铁质-超镁铁质岩呈东西向带状分布,断续出露长约300km,宽约30km。该镁铁质-超镁铁质岩带内铜镍矿床(点)较为发育,克布为该带内一个中 小型铜镍硫化物矿床。克布镁铁质-超镁铁岩体出露面积约45km2,主要由辉长岩相和橄榄岩相组成,辉长岩相为岩体的主要岩相,橄榄岩相为主要的赋矿岩石,两个相带相伴产出,呈渐变过渡关系。本文采用LA ICP MS锆石U Pb法测年,获得克布斜长方辉橄榄岩年龄为2581±18Ma(MSWD=23),属于晚二叠世。岩石主、微量及稀土元素分析结果表明,岩石样品属铁质镁铁质-超镁铁质岩,具有拉斑玄武岩系列演化趋势,并相对富集大离子亲石元素(Rb、Sr、Ba),亏损高场强元素(Nb、Ta、Zr、Hf、Ti),以及具有轻稀土富集\[(La/Yb)N=247~1129\]的右倾型稀土配分模式。以橄榄石-熔体平衡原理估算克布镁铁质-超镁铁质岩体母岩浆的MgO含量为101%,FeO为121%,应为高镁的拉斑玄武质岩浆。综合分析认为,克布镁铁质-超镁铁质岩体应形成于后碰撞伸展阶段,岩浆源区由被消减板片交代的地幔楔物质和软流圈物质组成。橄榄石和辉石等富镁铁矿物的分离结晶和富硅地壳物质的混染可能对硫化物熔离富集成矿起到了关键性作用。
中文关键词:克布镁铁质-超镁铁质岩体  锆石U Pb年龄  地球化学  铜镍成矿作用  乌拉特中旗
 
Geochronological, Mineralogical and Lithogeochemical Studies of the Kebu Mafic-ultramafic Intrusion in Urad Middle Banner, Inner Mongolia
NameInstitution
DANG Zhicai1) Tianjin Institute of Geology and Mineral Resources, China Geological Survey, Tianjin, 300170, China
LI Junjian1) Tianjin Institute of Geology and Mineral Resources, China Geological Survey, Tianjin, 300170, China
FU Chao1) Tianjin Institute of Geology and Mineral Resources, China Geological Survey, Tianjin, 300170, China
TANG Wenlong1) Tianjin Institute of Geology and Mineral Resources, China Geological Survey, Tianjin, 300170, China
LIU Yue3) State Key Laboratory of Geological Process and Mineral Resources, China University of Geosciences, Beijing, 100083, China
ZHAO Zelin1) Tianjin Institute of Geology and Mineral Resources, China Geological Survey, Tianjin, 300170, China; 2) Graduate Department of Chinese Academy of Geological Sciences, Beijing, 100037, China
WU Xingyuan1) Tianjin Institute of Geology and Mineral Resources, China Geological Survey, Tianjin, 300170, China
SUN Hongwei1) Tianjin Institute of Geology and Mineral Resources, China Geological Survey, Tianjin, 300170, China
Abstract:Urad Middle Banner (Wulatezhongqi) in Inner Mongolia is tectonically located in the northwestern margin of North China Craton, belonging to the Langshan Baiyan Obo epicontinental rifting. Regionally, mafic ultramafic intrusions are distributed discontinuously along central Inner Mongolia, forming a 400 km long, 30 km wide magmatic belt. This belt hosts lots of Cu Ni (PGE) deposits/ occurrences, with the small medium sized Kebu Cu Ni deposit occurring in the Kebu massif. The Kebu massif, cropping out over an area of 45km2, consists of gabbro and olive facies. The gabbro facies is dominant litholgical facies for massif, whereas the olive facies hosts the main orebodies. The two facies occur together and present a transition relation. In this study, LA ICP MS U Pb dating of zircons yielded an age of 2581±18Ma (MSWD=23) for the Kebu plagio harzburgite, suggesting a Late Permain magmatic event. Geochemical analysis results show that the mafic ultramafic rocks from the Kebu massif belong to the tholetiitic series. These rocks are relatively enriched in large ion lithophile elements (eg. Rb, Sr, Ba,) and depleted in high field strength elements (eg. Nb, Ta, Zr, Hf, Ti), with right inclined REE distribution pattern and (La/Yb)N value of 247~1129. According to the Fo and Ni values of olivine which contains the highest Fo, MgO and FeO contents of parent magma were estimated to 101% and 121% respectively, indicating that the parent magma of the Kebu intrusion is a high MgO tholetiitic basalt. The comprehensive analysis shows that the Kebu mafic ultramafic intrusion might form in the post collisional tectonic setting, with magmatic source consisting of asthenospheric material and mantle wedge material, both of which were contaminated by previously subducted fluids. Crystallization fractionation of Fe and Mg rich minerals (such as olivine and pyroxene) and contamination of Si rich crust material might have played a key role in S saturation and subsequent sulfide segregation.
keywords:The Kebu mafic-ultramafic intrusion  Zircon U-Pb dating  Geochemistry  Cu-Ni mineralization  Urad Middle Banner
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