Redox and temperature conditions governing chemical and isotopic equilibration of CO2 and CH4 in volcanic-hydrothermal environments

与先前的假设相反，最近对希腊的尼西罗斯火山和意大利的维苏威火山的研究表明，甲烷和二氧化碳之间的化学和同位素平衡在低至320°C的温度下是可能的。在溶液中达到总体平衡，并且在蒸气分离之后两种气体的二次再平衡似乎只是次要的。这可能使CH 4-CO2地质温度计成为监测上升岩浆体上含水层温度变化的合适候选者，从而反映火山活动的状态。此外，它们还有助于为地热能勘探目的确定含水层并说明其特性。然而，需要更多关于火山热液系统的综合数据（成分和同位素），以确定CH 4-CO2平衡的先决条件，其在自然界中的相对存在，因此，其对火山风险评估的意义。因此，我们打算调查的化学和同位素组成的火山气体从三个构造不同的火山设置在意大利。

Contrary to what has been previously assumed, recent investigations on Nisyros volcano, Greece, and Vesuvio, Italy, imply that chemical and isotopic equilibration between CH4 and CO2 is possible down to temperatures as low as 320°C. Overall equilibrium is attained in solution and secondary re-equilibration of both gases after vapor separation seems to be only of minor importance. This possibly makes the CH4-C02 geothermometers suitable candidates to monitor temperature variations of aquifers overlying rising magma bodies and, hence, to reflect the state of volcanic activity. Furthermore, they could help to identify and characterize aquifers for the purpose of geothermal energy exploration. However, more combined data (compositional and isotopic) on volcanic-hydrothermal systems is needed to identify the prerequisites for CH4-C02 equilibration, its relative occurrence in nature and, hence, its significance for volcanic risk evaluation. We, therefore, intend to investigate the chemical and isotopic composition of fumarolic gases emitted from three tectonically distinct volcanic settings in Italy.