The study of active and fossil hydrothermal systems shows clay minerals to be a fundamental tool for the identification and characterization of hydrothermal alteration facies. The occurrence and composition of hydrothermal alteration facies could provide useful information on the physicochemical conditions of the hydrothermal activity affecting a rock volume. In particular, clay minerals (i.e., smectite group, chlorite, illite, kaoline group, pyrophyllite, biotite) are pivotal for extrapolating important parameters that strongly affect the development of water/rock interaction processes such as the temperature and pH of the hydrothermal environment. This work aims to give a general reference scheme concerning the occurrence of clay minerals in hydrothermal alteration paragenesis, their significance, and the information that can be deduced by their presence and chemical composition, with some examples from active and fossil hydrothermal systems around the world. The main mineralogical geothermometers based on chlorite and illite composition are presented, together with the use of hydrogen and oxygen isotope investigation of clay minerals in hydrothermal systems. These techniques provide a useful tool for the reconstruction of the origin and evolution of fluids involved in hydrothermal alteration. Finally, a list of oxygen and hydrogen fractionation factor equations between the main clay minerals and water is also provided.

中文翻译：

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热液系统中的粘土矿物

对活跃和化石热液系统的研究表明，粘土矿物是识别和表征热液蚀变相的基本工具。热液蚀变相的发生和组成可以为影响岩石体积的热液活动的理化条件提供有用的信息。尤其是，粘土矿物（即绿土，亚氯酸盐，伊利石，高岭土，叶蜡石，黑云母）对于推断重要影响水/岩石相互作用过程（例如水热环境的温度和pH）的重要参数至关重要。这项工作旨在提供有关热液蚀变共生中粘土矿物的发生，其意义的一般参考方案，以及可以通过它们的存在和化学组成来推断的信息，其中一些例子来自世界各地的活跃和化石热液系统。介绍了基于绿泥石和伊利石成分的主要矿物地热仪，以及在水热系统中利用粘土矿物中的氢和氧同位素进行研究。这些技术为重建与热液蚀变有关的流体的起源和演化提供了有用的工具。最后，还提供了主要粘土矿物和水之间的氧和氢分馏因子方程式的列表。以及在水热系统中使用氢和氧同位素研究粘土矿物。这些技术为重建与热液蚀变有关的流体的起源和演化提供了有用的工具。最后，还提供了主要粘土矿物和水之间的氧和氢分馏因子方程式的列表。以及在水热系统中使用氢和氧同位素研究粘土矿物。这些技术为重建与热液蚀变有关的流体的起源和演化提供了有用的工具。最后，还提供了主要粘土矿物和水之间的氧和氢分馏因子方程式的列表。