Abstract

The clay minerals in the Upper Pleistocene sediments from DSDP Hole 478 (a drilled depth of 464 m) located in the central area of the Guaymas Basin, Gulf of California, are studied. The composition of the clay minerals and their quantitative proportions in natural mixtures are determined by modeling of X-ray diffraction patterns for oriented specimens of finely dispersed particles. The terrigenous clay minerals are mainly dioctahedral (mixed-layer smectite–illite is dominant, the amount of illite is smaller) with admixtures of chlorite and kaolinite. They are distributed throughout the entire sedimentary section, except for thermally altered sediments from the contact zones with the top of the sills, where terrigenous dioctahedral clay minerals disappear, except for illite, and are substituted by trioctahedral mixed-layer chlorite–smectite and corrensite–chlorite; trioctahedral smectite also appears. Terrigenous illite is missing in the sediments at the base of the sedimentary cover exposed by the hole, on the top of the sill complex with a thickness of no less than 125 m.

中文翻译：

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加利福尼亚湾瓜伊马斯盆地中部沉积物中的粘土矿物

摘要

研究了位于加利福尼亚湾瓜伊马斯盆地中部的DSDP孔478（钻进深度464 m）上更新世沉积物中的粘土矿物。粘土矿物的组成及其在天然混合物中的定量比例是通过对细分散颗粒的定向试样的X射线衍射图进行建模来确定的。陆源粘土矿物主要是八面体（混合层蒙脱石-伊利石为主，伊利石的量较小），以及绿泥石和高岭石的混合物。它们分布在整个沉积区，除了与基石顶部接触区的热蚀变沉积物外，陆上的二八面体粘土矿物消失了，伊利石除外。并被三面体混合层亚氯酸盐-蒙脱石和堇青石-亚氯酸盐代替；三面体蒙脱石也出现了。在基岩复合体顶部，厚度不小于125 m的沉积物覆盖层的底部，孔中露出的陆源伊利石丢失。