| The ＂CO2-rich gas vents＂ of Mt. Amiata volcano （Tuscany, Central Italy）： Geochemistry,genetic mechanism and hazard evaluation |
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| 作者姓名： | Franco Tassi Orlando Vaselli Elena Lognoli Fabrizio Cuccoli Barbara Nisi Elena Ramaldi Sandro Moretti Luca Lombardi Bruno Capaccioni |
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| 作者单位： | [1]Department of Earth Sciences, Via G La Pira 4, 50121, University of Florence, Italy [2]U.O. CNIT, Dept. Electronics ＆ Telecommunications, Via di Santa Marta, 3 - 50139 Florence, Italy [3]Department of Earth and Environmental Sciences, P.zza Porto S. Donato, 1, 40126, Bologna, Italy |
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| 摘 要： | Mt. Amiata （Southern Tuscany, Central Italy） is an extinct Quaternary volcano located in an area still marked by high heat-flow that is caused by deep seated （6-10 km） hot masses related to Pliocene magmatic activity. The anomalous geothermal gradient gives rise, within the Mesozoic limestone formation （Tuscan series）, to geothermal systems that fed the Ca-SO4 thermal springs characterizing this area. Besides of thermal fluids, several cold, dry CO2-rich gas emissions seep out on the NE flank of the volcano. These gas vents mostly consist of large sub-circular craters at variable depth and diameter （5-15 m and 10-50 m, respectively）, and represent a serious hazard for the local population, as testified by the several asphyxia casualties that have been repeatedly occurred within these morphological depressions. In this work, the chemical and isotopic compositions of the Mt. Amiata ＂CO2-rich gas vents＂ and the estimation of both the CO2 flux from the soil and the CO2 distribution in air of their surroundings, has been carried out in order to： （1） assess the origin of gases, （2） recognize the mechanism of formation for these gas emissions and their relationship with local tectonics, and （3） to evaluate the CO2 hazard in the high flux emanations. The chemical composition of the gases is largely dominated by CO2 （up to 98 % by vol） and shows relatively high concentrations of N2, CH4 and H2S （up to 1.1%, 0.9% and 3.9 % by vol, respectively）. These features, coupled with the carbon and nitrogen isotopic signatures, suggest that the origin of the main gas compounds may be related to the contribution of deep （i.e., thermometamorphic processes on carbonate formations for CO2） and shallow （i.e. thermal decomposition of organic material for CH4, N2 and H2S） sources.
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| 关 键 词： | 二氧化碳 烟气 火山 地球化学 起源机制 |
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