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首页> 外文期刊>Contributions to Mineralogy and Petrology >Dissolution-precipitation processes governing the carbonation and silicification of the serpentinite sole of the New Caledonia ophiolite
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Dissolution-precipitation processes governing the carbonation and silicification of the serpentinite sole of the New Caledonia ophiolite

机译：溶解-沉淀过程控制新喀里多尼亚蛇绿岩蛇纹岩岩层的碳化和硅化作用

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摘要

The weathering of mantle peridotite tectoni-cally exposed to the atmosphere leads commonly to natural carbonation processes. Extensive cryptocrystalline mag-nesite veins and stock-work are widespread in the serpentinite sole of the New Caledonia ophiolite. Silica is systematically associated with magnesite. It is commonly admitted that Mg and Si are released during the laterization of overlying peridotites. Thus, the occurrence of these veins is generally attributed to a per descensum mechanism that involves the infiltration of meteoric waters enriched in dissolved atmospheric CO_2. In this study, we investigate serpentinite carbonation processes, and related silicification, based on a detailed petrographic and crystal chemical study of serpentinites. The relationships between serpentine and alteration products are described using an original method for the analysis of micro-X-ray fluorescence images performed at the centimeter scale. Our investigations highlight a carbonation mechanism, together with precipi- tation of amorphous silica and sepiolite, based on a dissolution-precipitation process. In contrast with the per descensum Mg/Si-enrichment model that is mainly concentrated in rock fractures, dissolution-precipitation process is much more pervasive. Thus, although the texture of rocks remains relatively preserved, this process extends more widely into the rock and may represent a major part of total carbonation of the ophiolite.
机译：暴露于大气的地幔橄榄岩的构造风化通常导致自然的碳化过程。在新喀里多尼亚蛇绿岩的蛇纹岩层中广泛分布着隐晶镁磁矿脉和储层。二氧化硅与菱镁矿有系统地关联。通常认为，在上覆橄榄岩的后期化过程中会释放出Mg和Si。因此，这些静脉的出现通常归因于逐日下降机制，该机制涉及富含溶解的大气CO_2的流域水的渗透。在这项研究中，我们基于蛇纹石的详细岩石学和晶体化学研究，研究蛇纹石的碳化过程和相关的硅化作用。蛇纹石和蚀变产物之间的关系使用原始方法进行了描述，该方法用于分析以厘米为单位的微X射线荧光图像。我们的研究着重说明了基于溶解-沉淀过程的碳化机理，以及无定形二氧化硅和海泡石的沉淀。与主要集中在岩石裂缝中的逐次增加的Mg / Si富集模型相反，溶解-沉淀过程更为普遍。因此，尽管岩石的质地保持相对保留，但是该过程更广泛地延伸到岩石中，并且可以代表蛇绿岩总碳酸盐化的主要部分。

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