勉略地区寒武纪含碳岩系稀土元素地球化学特征及成因意义  

REE Geochemical Characteristics of the Cambrian Carbonaceous Rock Series in the Mian-Lüe Region and Their Genetical Implications

作　　者：乔耿彪[1] 杨钟堂[1] 李智明[1] 杨晓勇[2] 蓝翔华[2] 

机构地区：[1]中国地质调查局西安地质矿产研究所,西安710054 [2]中国科学技术大学地球和空间科学学院,合肥230026

出　　处：《吉林大学学报（地球科学版）》2011年第4期1067-1076,共10页Journal of Jilin University：Earth Science Edition

基　　金：中国地质调查局地质调查项目(1212011085111);中央地质勘查基金试点项目(2007611007)

摘　　要：采用等离子质谱仪（ICP-MS）测试方法对岩石的稀土元素含量进行了测定,探讨了勉略地区寒武纪含碳岩系的稀土元素地球化学特征及其成因。研究表明：含碳岩系岩石的稀土元素总量（∑REE）总体变化不大,质量分数为（167.88~210.50）×10-6,平均为192.20×10-6;轻重稀土比值（LREE/HREE）为6.64~16.25,平均为11.52,显示轻稀土富集而重稀土亏损;含碳岩系岩石具明显的Ce负异常,δCeN值为0.58~0.90（平均为0.78）,表明其主要形成于干燥气候条件下的缺氧还原沉积环境,且为近陆边缘海（即浅海）沉积位置;本区含碳岩系岩石具明显的Eu负异常,δEuN值为0.47~0.83（平均为0.62）,说明其形成于被动大陆边缘,为低温成岩作用（〈250℃）下的正常海水及其沉积物;含碳岩系岩石的La/Yb-REE图解及La/Yb-Ce/La图解也表明其非热水沉积特征,为正常的海洋沉积环境,其物质可能主要来自正常海相沉积环境下较高石英含量的陆壳。The authors analyzed REE contents of the Cambrian carbonaceous rock series in the Mian-Lüe region by using ICP-MS method in order to investigate their geochemical characteristics and genetic implications.Some conclusions can be reached from the acquired analytical data：the carbonaceous rock series show narrow variation in the total contents of rare earth elements（∑REE）,from 167.88×10-6 to 210.50×10-6 with an average at 192.20×10-6;the ratios of LREE/HREE vary from 6.64 to 16.25 with an average at 11.52,showing relative enrichment of LREE and depletion in HREE;the carbonaceous rock series show remarkable negative Ce anomalies,varying from 0.58 to 0.90（0.78 on average）,suggesting that the carbonaceous rock series formed in a dry and anoxic sedimentary environment close to a marginal sea of continental slope;the carbonaceous rock series also show distinctly negative Eu anomalies,δEuN=0.47-0.83（0.62 on average）,suggesting that they formed in a passive continental margin environment as products of normal marine sediments under low temperature（250℃） diagenesis,consistent with the their geotectonic location in the northern margin of the Yangtze platform;according to the diagrams of La/Yb-Ce/La and La/Yb-REE,it is also confirmed that the carbonaceous rock series not formed in a hydrothermal sedimentary condition but in a normal marine condition with their main source materials coming from a continental crust with high quartz content.

关 键 词：含碳岩系 稀土元素 地球化学 干燥缺氧环境 非热水沉积 勉略地区 

分 类 号：P595[天文地球—地球化学]