(Table 1) Average composition of smectites of sediment core CRP-3@en

The aim of this work is to evaluate the origin of smectites in sediments of CRP-3 core (Victoria Land Basin, Antarctica), through TEM observations and microanalyses on smectite microparticles and XRD analyses of clay fractions. Smectites in the lower sedimentary section (between 602.05 and 815.86 mbsf), and in some levels of the central section of the core, are intermediate members of the beidellite-saponite series, with lower K and higher Mg contents in interlayer and higher cristallinity values. The clay fraction largely consists of smectite, that is regarded as authigenic. Smectites in the upper (between 6.60 and 101.69 mbsf) and in some other levels of the central section of the core are Al-Fe beidellites, with higher K and lower Mg contents in interlayer sites and lower values of crystallinity. In the clay fraction illite and chlorite also occur. These characteristics suggest that smectites in these sediments are detrital. Smectites in an igneous body (between 901.20 and 919.06 mbsf) have a homogeneous composition and are Al-rich beidellite-montmorillonites; the clay fraction is mostly composed by kaolinite with mixed-layer smectite-illite or kaolinite-smectite. Authigenic smectites probably formed from the alteration of volcanic material (pyroxenes, glasses) and/or through precipitation from fluids of possible hydrothermal origin.本研究旨在通过对CRP-3岩芯（南极洲维多利亚地盆地）沉积物中的蒙脱石微粒开展透射电子显微镜（TEM）观测与微区分析，以及对黏土组分开展X射线衍射（XRD）分析，探究该岩芯沉积物中蒙脱石的成因。 该岩芯下部沉积层段（602.05~815.86 米深海床以下深度（mbsf））以及中部层段的部分地层中产出的蒙脱石，属于贝得石-皂石系列的中间成员，其层间钾、镁含量分别偏低、偏高，且结晶度更高。该黏土组分主体由蒙脱石构成，被认为是自生成因矿物。 该岩芯上部层段（6.60~101.69 mbsf）以及中部层段的其他部分地层中产出的蒙脱石为铝铁贝得石，其层间钾含量偏高、镁含量偏低，且结晶度更低。该黏土组分中还含有伊利石与绿泥石。上述特征表明，该类沉积物中的蒙脱石为陆源碎屑成因。 位于901.20~919.06 mbsf的火成岩体中的蒙脱石成分均一，属于富铝贝得石-蒙脱石系列；该黏土组分主体由高岭石以及混层结构的蒙脱石-伊利石或高岭石-蒙脱石构成。 自生蒙脱石可能形成于火山物质（辉石、火山玻璃）的蚀变作用，或由可能为热液成因的流体沉淀形成。