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  

Lithofacies,geochemical characteristics and tectonic environment of Xilinhot Group,Inner Mongolia,China

作　　者：孙俊俊[1] 葛梦春[1] 周文孝[1] 于洋[1] 王仕海[1] 鲍建泉[1] 

机构地区：[1]中国地质大学(武汉)地球科学学院,湖北武汉430074

出　　处：《地学前缘》2012年第5期144-155,共12页Earth Science Frontiers

基　　金：中国地质调查局项目"内蒙古1:5万锡林浩特市等4幅区域地质调查"(1212010811005);"内蒙古1:25万锡林浩特市幅区域地质调查"(1212010510507)

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[1]。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)N=4.71～7.97),斜长角闪岩具有平坦型((La/Yb)N=0.74～0.95)和轻稀土元素微弱富集型((La/Yb)N=1.06～3.63)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;变质沉积岩形成于活动大陆边缘-大陆岛弧环境;变质基性火山岩形成于岛弧-弧后盆地。二者指示锡林浩特岩群形成于活动大陆边缘体系。The Xilinhot Group is an important part of Xilin Gol Complex in Xilin Gol micro-blocks in the eastern part of Inner Mongolia.This Group mainly consists of gneiss with amphibolite,magnetite-quartzite and granofels interlayers.The gneisses have middle LREE-rich REE pattern（（La/Yb）N=4.71-7.97）.The amphibolite has relatively flat REE（（La/Yb）N=0.74-0.95） or slightly enriched LREE（（La/Yb）N=1.06-3.63） pattern.The spider diagram of trace elements normalized by N-MORB of the amphibolites shows that their protoliths are mainly similar to the transitional basalts between mid-ocean ridge basalts（MORB） and volcanic arc basalts（VAB）.Petrography and various relevant geochemical discrimination diagrams show that the protoliths of gneiss are clastic subgreywacke and amphibolites are basalts transtional between tholeiitic and calc-alkaline.The gneisses were formed in active continental margins.The metabasic volcanic rocks displayed the features of the transitional type between island-arc and mid-oceanic basalt.Accordingly,they are suggested to be formed in island arc-back arc basin conditions.All of these characteristics indicate that Xilinhot Group was formed in active continental margin system.

关 键 词：锡林浩特岩群 锡林郭勒杂岩 片麻岩 斜长角闪岩 地球化学 

分 类 号：P588.3[天文地球—岩石学]