摘要
对扬子地块北缘贵池地层区从震旦系到三叠系沉积地层各种岩石的稀土元素组成研究表明，全剖面稀土平均含量（１２７μｇ／ｇ）低于沉积岩的平均含量（２３０μｇ），但与地台区（１２９μｇ／ｇ）十分接近。按岩类平均，页岩稀土含量最高（２３０μｇ／ｇ），砂岩及粉砂岩次之（２１３μｇ／ｇ），灰岩最低（１８μｎ／ｇ）。不同时代地层稀土含量受岩性控制，以碳酸盐岩为主的奥陶系（４０μｇ／ｇ）、三叠系地层（４４μｇ／ｇ）稀土含量最低，以陆源碎屑岩为主的志留系（２３１μｇ／ｇ）、泥盆系地层（２４８μｇ／ｇ）最高。不同岩性、不同时代的地层，尽管稀土含量有别，但稀土分布模式却很相似，构成一组右倾斜负铕异常的平行曲线，在∑（Ｌａ～Ｎｄ）－∑（Ｓｍ～Ｈｏ）－∑（Ｅｒ～Ｌｕ）三角图解上，各样品点很集中，反映本区稀土组成的均一性。相似的稀土组成表明，本区自震旦纪到三叠纪长期处于稳定的构造环境，具地台区的属性。沉积环境与世界典型地台区类似。江南古陆不是本区沉积物的来源区．可能来自北方古陆。
The study on REE compositions of Sinian to Triassic sedimentary strata from Guichi stratigraphic region located in northern margin of the Yangtze block indicates that average total REE concentration is 127μg/g which Is lower than average value of sedimentary rocks in the world(230 μg/g)and approximates to that of sedimentary rocks from the platforms(129 μg/g).Among different lithologies,the average total REE concentration of shales is the highest(230 μg/g),that of limestoneS is the lowest(18 μg/g)and that of sandstones and siltstones is in middle(213 μg/g).REE concentrations of strata of different geologic ages are controlled by lithology.REE concentrations of Ordovician and Triassic strata consisting mostly of carbonate rocks are the lowest(40 and 44 μg/g,respectively),the of Silulian and Devonian strata consisting mainly of terrestrial detrital rocks are the highest(231 and 248 μg/g,respectively).Sedimentary rocks of this study show very similar REE patterns with LREE enrichment and negative Eu anomaly regardless of lithology and stratigraphic age.The points of the samples are concentrated in the triangular diagram for ∑(La～Nd)-∑(Sin～Ho)-∑(Er～Lu),suggesting hompeneity of REE compositions and a stable environment for the studied region.Similarity between REE compositions of sedimentary rocks from the studied region and that from typical platforms of the world suggests the platform character of the studied region during Sinian to Triassic.Results of this study suggests that the provenance of the studied sedimentary rocks is not the Jiangnanian old land mass,but the old continent(s)from the north.
出处
《中国稀土学报》
CAS
CSCD
北大核心
1996年第3期254-260,共7页
Journal of the Chinese Society of Rare Earths
基金
国家自然科学基金
关键词
沉积地层
沉积环境
稀土元素
沉积学
Sedimentary strata,REE composition,sedimentary environment,Guichi straitigraphic region
