摘要
笔者采用等离子质谱仪(ICP-MS)方法对北秦岭大荆区奥陶纪—志留纪庙湾组黑色岩系岩石的稀土元素及V、Ni、Cr、U、Th等微量元素含量进行了测定。结果显示岩石轻稀土元素相对重稀土元素富集,Eu异常值δEu为0.63～10.61(绝多数大于1.54)多呈正异常,Ce异常值δCe为0.65～1.02(平均为0.893)异常微弱且有正负差异;U/Th值为0.38～4.07,w(V)/w(V+Ni)值为0.38～0.93以及w(Ce)/w(La)值为1.27～2.17。将这些特征值与前人研究成果对比,并利用La/Yb-Ce/La和La/Yb-REE判别图解判别后,认为北秦岭区庙湾组黑色岩系形成于活动陆缘一种干燥缺氧较深浅海环境,黑色岩系形成过程中有热液作用参与。
The abundances of rare earth elements and some trace elements such as V,Ni,Cr,U and Th of the black rock series from the Miaowan Formation in North Qinling Mountain were measured by using the ICP-MS method.The results show that the black rock series of the Miaowan Formation is usually of the LREE-enriched type,that the samples are characterized by slightly negative or positive Ce anomalies （δCe=0.65～1.02） and distinct positive Eu anomalies （with δEu mostly higher than 1.54）,and that the ratios of U/Th display a wide variation range from 0.38 to 4.07,the ratios of w （V） /w （V ＋Ni）（= 0.38～0.93） are normal,and the ratios of w （Ce）/w （La） （=1.27～2.17） are relatively high.A study of the parameters of REE and trace elements in comparison with the available data and an analysis of the La/Yb-Ce/La and La/Yb-REE diagrams reveal that the black rock series was formed in a dry,anoxic and shallow sea environment belonging to an active continental margin,with the participation of some hydrothermal fluids.
出处
《地球学报》
EI
CAS
CSCD
北大核心
2010年第1期73-82,共10页
Acta Geoscientica Sinica
基金
西北有色地勘局地勘院“陕西南部黑色岩系金属矿床成矿规律及找矿预测研究”(编号:地勘[2006])
中国地质调查局“昆仑-阿尔金成矿带地质矿产调查综合研究”(编号:1212010913015)联合资助
关键词
庙湾组
黑色岩系
稀土地球化学
干燥缺氧环境
北秦岭
Miaowan Formation
black rock series
REE geochemistry
dry and anoxic environment
Northern Qinling
