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| 鄂尔多斯盆地东胜地区直罗组砂岩的地球化学特征与物源分析 | |
| 引用本文： | 吴兆剑,韩效忠,易超,祁才吉,惠小朝,王明太.鄂尔多斯盆地东胜地区直罗组砂岩的地球化学特征与物源分析[J].现代地质,2013,27(3). |
| 作者姓名： | 吴兆剑 韩效忠 易超 祁才吉 惠小朝 王明太 |
| 作者单位： | 1. 中国地质大学地球科学与资源学院,北京100083;中煤地质工程总公司,北京100037 2. 中煤地质工程总公司,北京,100037 3. 核工业北京地质研究院,北京,100029 4. 中国地质大学地球科学与资源学院,北京100083;中化地质矿山总局地质研究院,河北涿州072754 |
| 基金项目： | 国家高技术研究发展计划("863"计划)项目 |
| 摘 要： | 沉积岩物源分析对揭示盆地砂体展布、物质组成、储集层性质及砂岩型铀矿床铀源等科学问题具有重要的意义。对取自鄂尔多斯盆地东北部8个钻井中的中侏罗统直罗组砂岩进行了详细的岩石学和地球化学研究,试图鉴别岩石的源区和形成的构造环境。研究表明,砂岩以中粗粒杂砂岩为主,其w(SiO2)值及w(Al2O3)/w(SiO2)值中等到较高,w(K2O)值相对较高,Fe2O3、MgO、TiO2含量较低,暗示碎屑物质的富长英质、贫镁铁质特征。Nb、Ta、Ti、P等不活动元素的强烈亏损和K、Rb、Sr、Ba等LILE的富集,共同指示源区具有明显的俯冲带的特征;而w(TFe2O3+MgO)-w(TiO2)、w(TFe2O3+MgO)-w(Al2O3)/w(SiO2)、w(Th)-w(Sc)-w(Zr)/10、w(Th)-w(Co)-w(Zr)/10等判别特征则表明砂岩源区岩石可能形成于大陆弧-活动大陆边缘环境。而且,在球粒陨石标准化分配模式中,LREE强烈富集,HREE无明显分异、有着较平坦的曲线,Eu无异常或表现为弱的正、负异常;在PAAS标准化曲线中,轻重稀土均无明显分异,仅Eu表现为明显正异常。本区直罗组砂岩与华北北缘显生宙闪长岩-花岗闪长岩有着很强的亲缘性。 |
| 关 键 词： | 鄂尔多斯盆地 东胜地区 直罗组砂岩 地球化学 物源分析 |
Geochemistry of Sandstones from the Middle Jurassic Zhiluo Formation,Dongsheng District, Northeastern Ordos Basin:Implications for Provenance and Tectonic Setting |
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| WU Zhao-jian , HAN Xiao-zhong , YI Chao , QI Cai-ji , HUI Xiao-chao , WANG Ming-tai.Geochemistry of Sandstones from the Middle Jurassic Zhiluo Formation,Dongsheng District, Northeastern Ordos Basin:Implications for Provenance and Tectonic Setting[J].Geoscience——Journal of Graduate School,China University of Geosciences,2013,27(3). | |
| Authors: | WU Zhao-jian HAN Xiao-zhong YI Chao QI Cai-ji HUI Xiao-chao WANG Ming-tai |
| Abstract: | The provenance analysis of sandstones are essential for the distribution and composition of sandbodies,reservoir properties and the sources of uranium,in the uranium deposits exploration.In this paper,detailed petrological and geochemical studies were carried out on the sandstones of Middle Jurassic Zhiluo Formation from 8 drilling cores in the northeastern Ordos Basin,in order to determine their provenance and tectonic setting.The samples are coarse greywacke with moderate to high SiO2 content and Al2O3/SiO2 ratio,a high content of K2O and a low content of Fe2O3,MgO and TiO2,which implies that these sandstones are in felsic,lacking of mafic materials.The rocks are enriched in large ion lithophile elements(LILEs,such as K,Rb,Sr and Ba),and depleted in high field strength elements(HFSEs,such as Nb,Ta,Ti and P).These features indicate that the source region have affinity of subduction-related tectonic setting.Similarly,other discrimination diagrams,such as(TFe2O3+MgO)-TiO2,(TFe2O3+MgO)-Al2O3/SiO2,Th-Sc-Zr/10,Th-Co-Zr/10,further suggest that the Zhiluo Formation sandstones were deposited as detritus from a continental island arc or active continental margin.Together with other characteristics,such as enrichment LREE,relatively flat HREE patterns,without or slightly Eu anomalies,flat patterns with positive Eu anomalies in the PAAS-normalized rare element plots,allowed us to conclude that the rocks are strongely related to the Phanerozoic granitoids from the northern margin of North China craton. |
| Keywords: | Ordos Basin Dongsheng district Zhiluo Formation sandstone geochemistry provenance analysis |
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