Fluids trapped in speleothems have an enormous potential in frontier fields of paleoclimate and paleohydrological research. This potential is, however, hampered by diverse scientific and technical limitations, among which the lack of a systematic methodology for genetically characterizing fluid inclusions is a major one, as these can have different origins, and thus, the trapped fluid (usually water), different meanings. In this work, we propose a systematic petrological classification of fluid inclusions, based on: 1) the temporal relation between fluid inclusions and the host calcite, 2) the spatial relation between fluid inclusions and the “crystallites” and crystals aggregates, and 3) the phases (water, air) trapped inside fluid inclusions. The first criterion allows dividing fluid inclusions in two main categories: primary and secondary, whose identification is critical in any research based on trapped fluids. The other two criteria allow the definition of eight types of primary and four types of secondary fluid inclusions.Primary fluid inclusions contain the drip water that fed stalagmites at the time of crystal growth, and can be intercrystalline, i.e., located between adjacent crystallites, or intracrystalline, i.e., with the fluid trapped within crystallites. We differentiate six main types among the intercrystalline fluid inclusions (elongate, thorn-shaped, down-arrow, interbranch, macro-elongate, and bucket) and other two among intracrystalline inclusions (pyriform and boudin). In primary inclusions, water is the main phase, while gas is much less abundant. The presence of gas could be related to slow drip rates or degassing in the cave, but also to later leakage due to changes in temperature and humidity often occurring during inadequate handling of speleothem samples.Secondary fluid inclusions were clearly related to younger water inlet through stratigraphic disruptions or unconformities. They are formed after water infiltration, but sealed before the renewed crystal growth. We differentiate four main types of secondary inclusions: interconnected, rounded, triangular, and vertical fluid inclusions. The identification of primary and secondary fluid inclusions in speleothems is a key for interpretation in paleoclimate studies.Integration of petrological results allow establishment of three different genetic scenarios for the formation of fluid inclusions, whose identification can be relevant because of their predictive character.

中文翻译：

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方解石石笋中的流体包裹岩相学：对夹带过程的影响

被困在洞穴中的流体在古气候和古水文研究的前沿领域具有巨大的潜力。然而，这种潜力受到各种科学和技术限制的阻碍，其中一个主要问题是缺乏对流体包裹体进行遗传表征的系统方法，因为这些包裹体可能具有不同的来源，因此被困流体（通常是水）、不同的含义。在这项工作中，我们提出了流体包裹体的系统岩石学分类，基于：1) 流体包裹体与主方解石之间的时间关系，2) 流体包裹体与“微晶”和晶体集合体之间的空间关系，以及 3)流体包裹体中的相（水、空气）。第一个标准允许将流体包裹体分为两个主要类别：主要和次要，在任何基于被困流体的研究中，其识别都是至关重要的。另外两个标准允许定义八种原生流体包裹体和四种次生流体包裹体。原生流体包裹体包含晶体生长时馈入石笋的滴水，可以是晶间，即位于相邻微晶之间，或晶内，即流体被困在微晶内。我们将晶间流体包裹体分为六种主要类型（细长形、刺形、向下箭头、分支间、宏观细长形和桶形包裹体）和其他两种晶内包裹体（梨形和鲍丁形）。在初级包裹体中，水是主要相，而气体的含量要少得多。气体的存在可能与缓慢的滴速或洞穴中的脱气有关，以及由于温度和湿度变化而导致的后期泄漏，这些变化经常发生在洞穴样品处理不当期间。二次流体包裹体显然与地层破裂或不整合导致的较年轻的水入口有关。它们是在渗水后形成的，但在新的晶体生长之前被密封。我们区分四种主要类型的次生包裹体：互连、圆形、三角形和垂直流体包裹体。洞穴中原生和次生流体包裹体的识别是古气候研究解释的关键。岩石学结果的整合允许建立流体包裹体形成的三种不同的遗传场景，由于它们的预测特性，识别可能具有相关性。