茂名油柑窝组油页岩元素地球化学特征及其地质意义  

Geochemical Characteristics and the Geological Significance of Oil Shales from the Youganwo Formation,Maoming Basin,China

作　　者：周圆圆[1,2] 邱楠生[1,2] 腾格尔[3] 王杰[3] 曹涛涛[3] 罗厚勇[3] 

机构地区：[1]中国石油大学(北京)油气资源与探测国家重点实验室,北京102249 [2]中国石油大学(北京)盆地与油藏研究中心,北京102249 [3]中石化石油勘探开发研究院无锡石油地质研究所,江苏无锡214151

出　　处：《矿物岩石地球化学通报》2016年第6期1270-1279,共10页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学青年基金项目(41503033)

摘　　要：结合茂名盆地茂页1井油柑窝组24个油页岩样品的主量元素、微量元素和稀土元素进行测试分析,在综合研究油柑窝组油页岩元素地球化学特征的基础上,探讨了茂名盆地油柑窝组油页岩沉积时期物源属性、源区沉积环境等。结果表明:油页岩样品Th、U和Pb元素富集,Zr、Cr、Hf等元素亏损,具有明显的轻稀土富集、Eu负异常以及Ce负异常等壳源物质的特征。化学蚀变指数(CIA)和Zr/Sc-Th/Sc图解表明物源区经历了强烈的风化作用以及明显的沉积再循环过程。在La/Th-Hf和La/Yb-ΣREE源岩判别图解分析的基础上,结合Eu负异常所指示的源岩长英质特性,认为茂名盆地油柑窝组油页岩物源具有多样性,主要来源于上地壳的长英质岩,推测可能为长英质火山岩、花岗岩和沉积岩的混合物。通过分析Sr/Cu、Mg O/Ca O等参数,认为油页岩形成时水体为淡水介质,沉积早期水体较浅,中晚期水体逐渐加深,属于温暖潮湿的气候背景,综合判断其沉积环境由早期弱还原湖沼相逐渐向半深湖一深湖相过渡。Geochemical elements of oil shale in the Maoming Basin were analyzed to discuss provenance attribute and dep-ositional environment of the Youganwo formation.Experimental date of the major elements,trace elements and rare earth elements of 24samples from the Maoye 1 well were examined.The analyzed oil shale samples were characterized by enrich-ment of Th,U,Rb and LREE,depleted of Zr,Cr and Hf,negative Eu and Ce anomalies,indicating that these samples were originated from continental crust.The chemical index of alteration（CIA）values and the Zr/Sc-Th/Sc diagrams indi-cate that source rocks had undergone intense chemical weathering and deposition recirculation.Based on the La/Th-Hf and La/Yb-REE diagrams and the negative anomaly of Eu element,the oil shale in the Maoming Basin has diverse sources, which mainly came from felsic source region of the upper crust or the mixture of felsic volcanic rocks,granite and sedimen-tary rocks.Ratios of the Sr/Cu,MgO/CaO suggest that oil shale was formed in fresh water under warm and humid cli-mate,shallow water column became deeper during the middle and late sedimentary period.The depositional environment is interpreted to be limnetic with weak reduction at the early stage and gradually turned into semi-deep to deep lacustrine.

关 键 词：油页岩 元素地球化学 物源区 沉积环境 茂名盆地 油柑窝组 

分 类 号：P618.12[天文地球—矿床学]