Characterization of mixed-layer illite-smectite from bentonites using microscopic, chemical, and X-ray methods: Constraints on the smectite-to-illite transformation mechanism
Characterization of mixed-layer illite-smectite from bentonites using microscopic, chemical, and X-ray methods: Constraints on the smectite-to-illite transformation mechanism
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DOI：
10.2138/am-1998-7-808
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发表时间：
1998-08
影响因子：
3.1
通讯作者：
J. Cuadros;S. Altaner
中科院分区：
文献类型：
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作者：
J. Cuadros;S. Altaner
本文研究了北美和欧洲不同地区的28个上新世-奥陶纪成岩膨润土样品中的伊/蒙混合层（<1或0.5 μm粒级），探讨了蒙皂石向伊利石转化的机制。XRD测量的伊利石含量范围为3 - 100%，层序从R = 0到R ≥ 3连续变化。XRD多型分析表明，随着伊利石化的进行，ES从主要的顺式空位结构变为反式空位结构，尽管数据中存在相当大的分散。伊利石在I/S中没有从IMd到1 M多型体的演化，具有渐进伊利化。氮的微探针化学分析和燃烧分析表明，NH+4占总固定阳离子含量的9-22%。我们计算出层间电荷为伊利石端员的1.5每O20（OH 4）。样品形态进行了研究，原子力显微镜，这表明在整个I/S系列恒定的纵横比和粒径。颗粒厚度随伊利石百分比的增加而增加。I/S粘土的氧同位素组成没有显示出任何系统的趋势。我们的研究结果表明，伊利化膨润土I/S的收益通过固态机制，与本地晶格重排，允许结构（八面体顺/反占有）和化学变化在2：1层，并导致层间合并。
Abstract We studied mixed-layer illite-smectite (I/S) (<1 or 0.5 μm size fractions) in 28 diagenetic bentonite samples, Pliocene to Ordovician in age, from different locations in North America and Europe to investigate the smectite-to-illite transformation mechanism. XRD- measured illite contents ranged from 3 to 100%, and layer ordering varied continuously from R = 0 to R ≥ 3. XRD polytype analysis showed that with progressive illitization, ES changes from a predominantly cis-vacant to a trans-vacant structure, although considerable scatter is present in the data. There is no evolution of illite in the I/S from IMd to 1M polytypes with progressive illitization. Microprobe chemical analysis and combustion analysis for N showed that NH+4 comprised 9-22% of the total fixed cation content. We calculated an interlayer charge for the illite end-member of 1.5 per O20(OH4). Sample morphology was studied by atomic force microscopy, which showed a constant aspect ratio and particle diameter over the whole I/S series. Particle thickness increased with percent illite. Oxygen isotope compositions of the I/S clays did not display any systematic trends. Our results suggest that illitization of bentonite I/S proceeds via a solid-state mechanism, with local lattice rearrangements that permit structural (octahedral cis/trans occupancy) and chemical changes in 2:1 layers and cause interlayer coalescence.