Abstract White (Mg-rich) and green (Ni-rich) clay infillings (“deweylite”/“garnierite”) found in serpentine veins of faulted peridotite formations from New Caledonia consist of an intimate mixture of fine-grained and poorly ordered 1:1 and 2:1 layer silicates, commonly referred to as non-expandable serpentine-like (SL) and talc-like (TL) minerals. New data on the swelling and shrinking capacity of these layer silicates were gathered from X‑ray diffraction (XRD) after saturation of the clay fractions with different cations (Ca2+, Li+, K+), ethylene glycol (EG) solvation, and heat treatments. Simultaneously, layer charge distribution and vacancy density, respectively, were investigated by FTIR spectroscopy on NH4-saturated clay fractions and XRD on Li-saturated clay fractions before and after heating (Hofmann Klemen treatment). Five clay infillings, with dominant 2:1 layer silicates and variable Ni contents, were selected for this study, from a large set of veinlets, according to their swelling capacity. The crystal chemistry of these samples was characterized by FTIR spectroscopy and bulk chemical analyses. The swelling ability of the clay infillings is attributed to the 2:1 layer silicates. It does not seem to be affected by the relative fraction of Mg and Ni in their octahedral sheets. In XRD patterns, the swelling ability is reflected by slight shifts of the basal reflection of the 2:1 layer silicates toward low angles for bulk samples and by splitting of the peak into two contributions for clay fractions saturated with Ca (or Li) and solvated with EG. The split increases with the swelling capacity of the sample. It originates mainly from octahedral-layer charge generated by vacant sites. Such results lead us to consider the 2:1 layer silicates of the infillings as an intimate mixture of non-expandable (TL) and expandable (stevensite) phases. In agreement with previous studies that suggested a contribution of hydrothermal processes in the alteration of serpentine species into 2:1 layer silicates, we propose that the proportion of expandable phases in the clay infillings (or vacancy sites in the octahedral sheets of the 2:1 layer silicates) could be used as an efficient means for assessing the temperature of their formation. Clay infillings mostly made of stevensite would have formed at ambient temperatures, whereas those consisting mainly of non-expandable TL would have formed at higher temperatures.

中文翻译：

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来自新喀里多尼亚断层橄榄岩蛇纹石脉的白色/绿色粘土填充物（“杜威岩”/“石榴石”）中混合滑石/硅镁石层的溶胀能力

摘要 在新喀里多尼亚断层橄榄岩地层的蛇纹岩脉中发现的白色（富含镁）和绿色（富含镍）粘土填充物（“杜威岩”/“石榴石”）由细粒和排列不良的 1 的紧密混合物组成： 1 和 2:1 层状硅酸盐，通常称为不可膨胀蛇纹石 (SL) 和滑石 (TL) 矿物。这些层状硅酸盐的溶胀和收缩能力的新数据是在粘土部分用不同的阳离子（Ca2+、Li+、K+）、乙二醇 (EG) 溶剂化和热处理饱和后从 X 射线衍射 (XRD) 收集的。同时，分别通过 FTIR 光谱对 NH4 饱和粘土部分的层电荷分布和空位密度进行研究，并对 Li 饱和粘土部分进行 XRD 研究，在加热前后（Hofmann Klemen 处理）。五个粘土填充物，根据膨胀能力，从大量细脉中选择了占主导地位的 2:1 层硅酸盐和可变 Ni 含量的细脉用于本研究。这些样品的晶体化学特性通过 FTIR 光谱和大量化学分析进行表征。粘土填充物的膨胀能力归因于 2:1 层状硅酸盐。它似乎不受八面体片中 Mg 和 Ni 的相对分数的影响。在 XRD 图中，溶胀能力通过 2:1 层硅酸盐的基底反射向散装样品的低角度的轻微偏移以及通过将峰分裂为用 Ca（或 Li）饱和和溶剂化的粘土部分的两个贡献来反映与EG。分裂随着样品的溶胀能力而增加。它主要来源于空位产生的八面体层电荷。这样的结果使我们将填充物的 2:1 层硅酸盐视为不可膨胀 (TL) 和可膨胀 (硅镁石) 相的紧密混合物。与之前的研究表明热液过程对蛇纹石物种转变为 2:1 层状硅酸盐的贡献一致，我们提出粘土填充物中可膨胀相的比例（或 2:1 八面体片中的空位）层硅酸盐）可用作评估其形成温度的有效手段。主要由硅镁石制成的粘土填充物会在环境温度下形成，而主要由不可膨胀的 TL 组成的粘土填充物会在较高温度下形成。填充物的 1 层硅酸盐是不可膨胀 (TL) 和可膨胀 (硅镁石) 相的紧密混合物。与之前的研究表明热液过程对蛇纹石物种转变为 2:1 层状硅酸盐的贡献一致，我们提出粘土填充物中可膨胀相的比例（或 2:1 八面体片中的空位）层硅酸盐）可用作评估其形成温度的有效手段。主要由硅镁石制成的粘土填充物会在环境温度下形成，而主要由不可膨胀的 TL 组成的粘土填充物会在较高温度下形成。填充物的 1 层硅酸盐是不可膨胀 (TL) 和可膨胀 (硅镁石) 相的紧密混合物。与之前的研究表明热液过程对蛇纹石物种转变为 2:1 层状硅酸盐的贡献一致，我们提出粘土填充物中可膨胀相的比例（或 2:1 八面体片中的空位）层硅酸盐）可用作评估其形成温度的有效手段。主要由硅镁石制成的粘土填充物会在环境温度下形成，而主要由不可膨胀的 TL 组成的粘土填充物会在较高温度下形成。1 层硅酸盐，我们建议粘土填充物中可膨胀相的比例（或 2:1 层硅酸盐八面体片中的空位）可用作评估其形成温度的有效手段。主要由硅镁石制成的粘土填充物会在环境温度下形成，而主要由不可膨胀的 TL 组成的粘土填充物会在较高温度下形成。1 层硅酸盐，我们建议粘土填充物中可膨胀相的比例（或 2:1 层硅酸盐八面体片中的空位）可用作评估其形成温度的有效手段。主要由硅镁石制成的粘土填充物会在环境温度下形成，而主要由不可膨胀的 TL 组成的粘土填充物会在较高温度下形成。