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大小:1.47 MB
页数:12页
时间:2020-04-30
《内蒙古锡林浩特岩群岩相学、地球化学特征及构造环境分析.pdf》由会员上传分享,免费在线阅读,更多相关内容在行业资料-天天文库。
1、第210912卷年第95月期ScienceFron地tie学rs前(C缘hin(a中U国niv地er质sity大o学fG(e北os京eien)e;es北(B京eij大ing学);)PekingUniversity)Vo1.19No.5Earth一—内蒙古锡林浩特岩群岩相学、地球化学特征及构造环境分析孙俊俊,葛梦春,周文孝,于洋,王仕海,鲍建泉中国地质大学(武汉)地球科学学院,湖北武汉430074SunJunjun,GeMengchun,ZhouWenxiao,YuYang,WangShihai,BaGJianquanFacultyofEarthScie
2、nces,ChinaUniversityofGeosciences(Wuhan),Wuhan430074,ChinaSunJunjun,GeMengchun,ZhouWenxiao,eta1.Lithofacies,geochemicalcharacteristicsandtectonicenvironmentofXilinhotGroup,InnerMongolia,China.EarthScienceFrontiers,2012,19(5):144—155Abstract:TheXilinhotGroupiSanimportantpartofXil
3、inGolComplexinXilinGolmicro-blocksintheeasternpartofInnerMongolia.ThisGroupmainlyconsistsofgneisswithamphibolite,magnetite-quartziteandgranofelsinterlayers.ThegneisseshavemiddleLREE-richREEpattern((La/Yb)N=4.71—7.97).Theam—phibolitehasrelativelyflatREE((La/Yb)N一0.74—0.95)orsligh
4、tlyenrichedLREE((La/Yb)N一1.06—3.63)pattern.ThespiderdiagramoftraceelementsnormalizedbvMORBoftheamphibolitesshowsthattheirprotolithsaremainlysimilartothetransitionalbasaltsbetweenmid-oceanridgebasalts(MORB)andvol—canicarcbasahs(VAB).Petrographyandvariousrelevantgeochemicaldiscrim
5、inationdiagramsshowthattheprotolithsofgneissareclasticsubgreywackeandamphibolitesarebasaltstranstionalbetweentholeiiticandcalc-alkaline.Thegneisseswereformedinactivecontinenta1margins.Themetabasicvolcanicrocksdisplayedthefeaturesofthetransitionaltypebetweenisland-arcandmid-ocean
6、icbasalt.Accordingly,theyaresuggestedtobeformedinislandarc-backarcbasinconditions.AllofthesecharacteristicsindicatethatXilinhotGroupwasformedinactivecontinentalmarginsystem.Keywords:XilinhotGroup;XilinGo1Complex;gneiss;amphibolite;geochemistry摘要:锡林浩特岩群是内蒙古中东部锡林郭勒微地块内原锡林郭勒杂岩的重要组成
7、部分,由一套片麻岩夹层状斜长角闪岩、磁铁石英岩和变粒岩等变质岩组成,形成于中元古代_】]。岩群中片麻岩样品显示轻稀土元素富集的中等分异特征((La/Yb)w一4.71~7.97),斜长角闪岩具有平坦型((La/Yb)N一0.74~o.95)和轻稀土元素微弱富集型((La/Yb)w=1.O6~3.63)两种稀土元素配分模式。在微量元素N-MORB标准化图解中,斜长角闪岩显示出洋中脊玄武岩和岛弧玄武岩的过渡类型特征。同时结合岩相学和岩石地球化学图解分析,推断片麻岩原岩为富含泥质的亚杂砂岩,而斜长角闪岩原岩为一套具有拉斑质到钙碱性过渡型特征的玄武岩;变质沉积
8、岩形成于活动大陆边缘一大陆岛弧环境;变质基性火山岩形成于岛弧一弧后盆地。二者指示锡林浩特岩群形
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