摘要
对鄂尔多斯盆地南缘下石盒子组碎屑岩的主量、微量及稀土元素等进行分析,研究鄂尔多斯盆地南缘下石盒子组碎屑岩地球化学特征,探讨其物源组成及源区构造环境。研究认为,研究区砂岩较泥岩含有较高的SiO2,而泥岩较砂岩含有较高的铁镁质组分和含钾矿物。砂岩和泥岩样品的微量元素组成与上地壳相似,均亏损Nb,Sr元素,泥岩还富集Ni,Cr元素,砂岩中则主要富集Zr,Hf元素。稀土元素标准化配分曲线均呈现轻稀土富集、重稀土亏损和Eu,Ce负异常特征。下石盒子组碎屑岩物源以酸性岩和少量基性岩为主,且遭受了低—中等程度的化学风化作用,在碎屑岩中混有少量来自被动大陆边缘并经历了沉积分选和再循环的古老物质加入。构造背景判别表明,该碎屑岩主要形成于大陆岛弧和活动大陆边缘环境。综合北秦岭构造带在二叠纪大幅度隆升的区域地质背景推断,北秦岭地区秦岭群、宽坪群变质岩、早期花岗岩及再循环造山带中的低级副变质岩为鄂尔多斯盆地南缘下石盒子组碎屑岩提供了主要物源。
This study analyses the Xiashihezi Formation to study the major elements, trace elements and sedimentary geochemistry of clastic rare-earth elements of clastic rocks from the rocks from the Xiashihezi Formation in the south of Ordos Basin and discuss the provenance characteristic and structural environment. The results suggest that sandstone contains higher SiO2 and plagioclase content than mudstone; mudstone, however, occupies higher femic mineral and K-bearing than sandstone. The trace elements of these samples are similar to the upper crust, which is depleted in Nb and Sr elements. Mudstones are enriched with Ni and Cr elements and most of sandstones are rich in Zr and Hr. The REE patterns are characterized by LREE enrichment, flat HREE, and negative Eu and Ce anoma- lies. Characteristics of samples from the Xiashihezi Formation show that rocks in the source come from upper crust and mainly consist of felsic rocks with a small amount of granite. And source underwent middle intense chemical weathering and was mixed with ancient sediments recycled from passive continental margin. Tectonic setting dis- criminations suggest that rocks in the source were mainly formed in the continental arc and active continental mar- gin. Combining the geological setting that North Qinling orogenic belt had raised by large amplitude during the Per- mian infers that the material component of the source rocks tended to be related to the metamorphic rocks and gran- ite from Qinling Group and Kuanping Group of the North Qinling orogenic belt.
出处
《西北大学学报（自然科学版）》
CAS
CSCD
北大核心
2013年第5期765-775,共11页
Journal of Northwest University（Natural Science Edition）
基金
国家重大基础研究“973”基金资助项目(2003CB214601)
关键词
鄂尔多斯盆地南缘
下石盒子组
碎屑岩
地球化学
the South of Ordos Basin
Xiashihezi Formation
clastic rocks
geochemistry
作者简介
罗婷婷,女,新疆乌鲁木齐人,西北大学博士生,从事油气资源勘探评价研究.
