地质学报2018，Vol.92Issue(2)：278-297,20.
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
Geochronological, Mineralogical and Lithogeochemical Studies of the Kebu Mafic-ultramafic Intrusion in Urad Middle Banner, Inner Mongolia
摘要
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 45km2,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.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Key words
The Kebu mafic-ultramafic intrusion/Zircon U-Pb dating/Geochemistry/Cu-Ni mineralization/Urad Middle Banner引用本文复制引用
党智财,李俊建,付超,唐文龙,刘跃,赵泽霖,吴兴源,孙宏伟..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,2018,92(2):278-297,20.基金项目
本文为中国地质调查局项目(编号DD20160112、1212010561510、1212010811061、1212011120330、12120114001201、1212011085488)和国土资源公益性行业科研专项(编号200811010)和国家国际科技合作项目(编号2012DFB20220)资助. （编号DD20160112、1212010561510、1212010811061、1212011120330、12120114001201、1212011085488）
