四川盆地及周缘五峰组-龙马溪组钾质斑脱岩特征及其地质意义  

The characteristics and geological significance of the K-bentonite in Wufeng Formation and Longmaxi Formation in Sichuan Basin and its peripheral areas

作　　者：卢斌[1] 邱振[1,2] 周杰[1] 董大忠[2] 王红岩[1] 薛华庆[1] 周尚文[1] 

机构地区：[1]中国石油勘探开发研究院廊坊分院,河北廊坊065007 [2]中国石油勘探开发研究院,北京100083

出　　处：《地质科学》2017年第1期186-202,共17页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金项目（编号：41602119）、国家重点基础研究发展计划“973”项目（编号：2013CB228001）和中石油廊坊分院项目（编号：XN41601,XN41603,XN11304）资助.

摘　　要：四川盆地及周缘五峰组-龙马溪组黑色页岩地层中斑脱岩广泛分布，蕴含着丰富的地球化学信息。开展相关矿物学（XRD）、主量元素（XRF），以及微量元素（ICP—MS）等分析，结合野外露头观察，对四川盆地及周缘五峰组-龙马溪组黑色页岩地层中斑脱岩进行了分析。研究结果表明：1）斑脱岩主要由伊利石、斜长石、石英等矿物组成；2）主量元素以SiO2、Al2O3、Fe2O3、K2O为主，其中K2O／Na2O介于15．54—270之间；3）微量元素富集Th、U、Pb、Zr、Hf、Ta等高场强元素（HFSE）和Rb、Cs、Ba等大离子亲石元素，亏损La、ce、Sr、Sm、Eu等元素；4）稀土元素∑REE介于19．58×10^-6-383．88×10^-6之间，平均值为105．43×10^-6，LREE／HREE介于0．74—12．67之间，平均值为3．93，总体表现为轻稀土（LREE）富集，而重稀土（HREE）亏损，轻、重稀土元素分异明显，Eu表现出-定的负异常，而Ce未出现明显异常。综合分析认为：1）四川盆地及周缘五峰组-龙马溪组斑脱岩具有高钾低钠的特点，与钾质斑脱岩特征相符，且五峰组与龙马溪组斑脱岩特征相似，火山灰物质来源相近；2）原岩构造环境主要为岛弧环境，同时也存在板内环境，火山灰主要来源于北部秦岭地区；3）火山灰可以提高海洋表层初级生产力，为优质页岩有机质形成提供物质基础。The K-bentonite which contains abundant geochemical information is widely distributed in Wufeng Formation and Longmaxi Formation in Sichuan Basin and its peripheral areas. In order to make a further study of the geological significance of the K-bentonite in black shale, we have learned the K-bentonite by the methods of XRD, XRF, ICP-MS and combined with the outcrop observation. Researches show that the bentonite in the study area mainly composed of illite, plagioclase, quartz and other mineral composition. The main elements mainly composed of SiO2, A1203, Fe203, K20 and the K20/Na2O is 15.54 - 270. The trace elements are rich in Th, U, Pb, Zr, Hf, TaandRb, Cs, Ba, and deplete in La, Ce, Sr, Sm, Eu. The ∑REEis19.58×10^-6-383.88×10^-6, average is 105.43×10^-6 ; LREE/HREE is 0.74 - 12.67, average is 3.93; and rich in LREE, deplete in HREE. The Light and heavy rare earth elements differentiation is obvious, Eu negative abnormity, and there is no evidently Ce abnormity. Comprehensive analysis suggests that： 1） The bentonites in Wufeng Formation and Longmaxi Formation in Sichuan Basin and its peripheral areas have the characteristics of high potassium low sodium, and coincide with the K-bentonite. The bentonites have similar characteristics with the same material sources. 2） The tectonic environment of original rock mainly is the island are environment, also exists certain intraplate environment, volcanic ash may mainly come from the North Qinling Mountains. 3） Volcanic ashes can improve the ocean surface primary productivity and provide material basis for the high quality shale.

关 键 词：四川盆地 五峰组 龙马溪组 钾质斑脱岩 地球化学 

分 类 号：P534.42[天文地球—古生物学与地层学]