Rare earth element geochemistry of the Permo-Carboniferous clastic sedimentary rocks from the Spiti Region,Tethys Himalaya:significance of Eu and Ce anomalies  

作　　者：Javid Ahmad Ganai Shaik Abdul Rashid 

机构地区：[1]Department of Geology,Aligarh Muslim University

出　　处：《Chinese Journal Of Geochemistry》2015年第2期252-264,共13页中国地球化学学报

基　　金：the Department of Science & Technology,New Delhi for supporting this research in the form of Research Grant(SR/S4/ES-422/2009) to SAR

摘　　要：包括沙岩和联系页岩， Siliciclastic 沉积岩石 NW Tethys Himalaya 从 Permo 含碳的 Kanawar 组织， Spiti 区域，印度 geochemically 被检验在 Himalaya 在上面的大陆人外壳中监视进化变化。岩石被一致稀土元素元素(REE ) 描绘有轻 REE 丰富的模式(La < 潜水艇 class= “ a-plus-plus ” > N </sub>/Yb<sub class= “ a-plus-plus ” > N </sub>?=?5.328.2) 和完全重的 REE 模式。REE 价值高(多达 281 ? ppm ) 与大否定 Eu 异例(avg。Eu/Eu *?=? 0.57 ) 。沉积的 REE 特征类似于 Archean 以后澳大利亚人页岩和北美的页岩的那些合成。La/Th 价值(avg。2.34 ) 对应于一相对陆上的火的岩石标准的 felsic 作文(G-1 的 La/Th ?=? 2.3 ) 。沉积的发展 felsic 作文可能在来源联系到普遍酸的活动。REE 模式和 Th/U 价值似乎被沉积环境以及由起源影响了。在一些沉积的积极 Ce 异例的存在可以是 post-depositional 过程的结果。而且， Permo 含碳的沉积显示甚至在短运输距离上，水力的排序能够集中足够的附件阶段影响 REE 作文并且开发否定 Eu 异例。高 REE， La/Yb，和 Th/U 内容和大否定 Eu 异例表明沉积在氧化环境被扔，建议地表的环境变得在在印度 craton 的含碳二叠的边界附近氧化。Siliciclastic sedimentary rocks,including sandstones and associated shales,from the Permo-Carboniferous Kanawar Group of NW Tethys Himalaya,Spiti Region,India were examined geochemically to monitor the evolutionary changes in the upper continental crust in the Himalaya.The rocks are characterized by consistent rare earth element（REE） patterns with light REE enrichment（LaN/YbN = 5.3-28.2） and flat heavy REE patterns.The∑REE values are high（up to 281 ppm） with large negative Eu anomalies（avg.Eu/Eu^＊ = 0.57）.The REE characteristics of the sediments are similar to those of postArchean Australian shales and North American shale composite.La/Th values（avg.2.34） correspond to a relatively felsic composition of the terrestrial igneous rocks standard（La/Th of G-1 = 2.3）.The evolved felsic composition of the sediments probably relates to widespread acidic activity in the source.The REE patterns and Th/U values seem to have been affected by the sedimentary environment as well as by the provenance.The presence of positive Ce anomalies in some sediments may be the result of post-depositional processes.Moreover,the Permo-Carboniferous sediments indicate that hydraulic sorting,even over short transport distances,is capable of concentrating enough accessory phases to influence REE composition and to develop negative Eu anomalies.High ∑REE,La/Yb,and Th/U contents and large negative Eu anomalies reveal that the sediments were deposited in an oxidizing environment,suggesting the surficial environment became oxidizing around the Carboniferous-Permian boundary in the Indian craton.

关 键 词：稀土元素地球化学 特提斯喜马拉雅 石炭二叠系 Ce异常 碎屑沉积岩 EU 氧化环境 硅质沉积岩 

分 类 号：P588.2[天文地球—岩石学] P595[天文地球—地质学]