准噶尔盆地南缘侏罗系泥岩黏土矿物组合及地球化学特征  

Jurassic Clay Mineral Assambleges in Mudstones and Geochemical Characteristics in the Southern Part of Junggar Basin

作　　者：王明振[1] 吴朝东[1,2] 王陆新[1] 房亚男[1] 李林林[1] 陈榕[1] 张晨晨[1] 

机构地区：[1]北京大学造山带与地壳演化教育部重点实验室,北京100871 [2]北京大学石油与天然气研究中心,北京100871

出　　处：《矿物岩石地球化学通报》2014年第4期421-430,共10页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家科技重大专项资助(2011ZX05009-001)

摘　　要：对准噶尔盆地南缘玛纳斯河剖面泥岩中黏土矿物的组合类型、微观形貌和地球化学特征进行了综合分析,讨论了侏罗纪古气候、古环境演化过程.结果表明,泥岩中主要矿物为黏土矿物、石英、长石,以及少量的方解石、赤铁矿等.黏土矿物组合类型分为两类.一类为伊利石蒙脱石混层矿物、伊利石、高岭石和绿泥石组合,主要分布在下侏罗统泥岩中;另一类为伊利石和蒙脱石组合,主要分布在上侏罗统泥岩中.扫描电子显微镜分析表明,黏土矿物结晶度较低,伊利石常呈丝状、叶片状,蒙脱石呈不规则板状分布在碎屑颗粒表面,片状伊利石/蒙脱石混层矿物存在于孔隙之中.其δCe为0.9～1.3,Eu呈负异常,La/Sc、La/Th、Th/Sc值则较高,指示源区母岩为长英质岩石类型.研究认为准南地区侏罗纪气候和沉积环境演化可划分为3个阶段：早侏罗世属于温暖湿润气候条件,以湖泊三角洲沉积为主;中侏罗世早期属于温干偏湿润气候条件,以湖泊沉积为主;中侏罗世中后期至晚侏罗世属于相对较冷干旱的气候条件,属于宽浅氧化湖盆沉积环境类型.This paper analyzes the combination of types, micro-morphology and geochemical features of clay minerals contained in the Jurassic mudstones along the Manasi river in the southern part of Junggar Basin. The Jurassic paleo-climate and paleo-environmental evolution is dicussed based on data of X-ray diffraction, SEM, X-ray fluorescence and ICP-MS. Results show that mudstones are composed of clay minerals, quartz, feldspar and accessory cal- cite and hematite. Clay mineral assemblages in the mudstones can be divided into two types： one is a mixed-layer of illite-smectite, illite, kaolinite and chlorite, which is distributed in the lower Jurassic strata, the other type is an assemblage of randomly distributed illite and smectite, which is present in the upper Jurassic strata. The crystallin- ity of clay minerals is low. Illite exists in a filamentous, leaf shape. Montmorillonite shows an irregular distribution of slabs in the surface of clastic particles. Based on the SEM and EDS results, we can conclude that illite/montmo- rillonite interlayers minerals also exist in pores. The δCe value ranges from 0.9 to 1.3. Eu shows a negative anomaly. All the La/Sc, La/Th, Th/Sc values are higher. This suggests that the provenance is a felsic rock. We con- clude that the evolution of the Jurassic climate and sedimentary environment along the southern part of the JunggarBasin can be divided into three stages： during the early Jurassic, the climate was warm and humid, and this area was dominated by fluvial and lacustrine-delta sediments; during the early to middle Jurassic, the climate became relatively warm and arid and this area developed lacustrine sediments; and lastly, from the middle to late middle Ju- rassic to the late Jurassic, the climate became relatively cold and dry and the sedimentary environment changed to a wide shallow lake basin.

关 键 词：古气候 古环境 风化蚀变指数 化学风化指数 

分 类 号：P588.22[天文地球—岩石学]