Arsenic in fumarolic gases of Vulcano (Aeolian Islands, Italy) from 1978 to 1993: Geochemical evidence from multivariate analysis
Arsenic in fumarolic gases of Vulcano (Aeolian Islands, Italy) from 1978 to 1993: Geochemical evidence from multivariate analysis
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1978 年至 1993 年武尔卡诺（意大利风神群岛）喷气孔气体中的砷：来自多变量分析的地球化学证据
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
G. Piccardi
中科院分区：
文献类型：
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作者：
S. Signorelli;A. Buccianti;M. Martini;G. Piccardi
对(意大利南部)伏尔卡诺岛的火山活动进行的一项地球化学监测计划收集了大量的观测资料，因此已知了1978年至1993年期间火山气体的主要化学成分。对伏尔卡诺富马林活动随时间的系统监测为研究富马林气体凝析物中砷浓度的变化提供了一个很好的机会，并将其与温度和气体的化学成分相关联。以前关于砷在富马酸气体中的行为的类似长时间的研究到目前为止还没有文献报道。为了研究大量变量之间的同时关系并评估它们随时间的变化，多变量方法是一种正确的工具。由于火山气体的化学成分由封闭(或组成)变量表示，因此采用对数比方法来克服诱导关联。通过考虑主成分分析的结果，可以得出以下结论：1)砷的行为主要受强烈的热液循环的影响，表现为元素与T、HF/H2O、NH3/H2O和H_2S/H_2O比值的多元组合，2)以随时间不断增加为特征的热液循环是火山系统的主要特征，在这个框架下，1984年发生的地震事件可能对流体循环起到了促进作用；3)气体温度升高与CO2/H2O和SO2/H2O比值所表示的典型岩浆贡献之间没有明显的联系。结果表明，砷与其他表征火山系统的物理化学参数的相关性有助于约束对其随时间演化的解释。如果该系统以热液作用为主，如瓦尔卡诺岛的热液作用，则情况尤其如此，那里的砷经历了密集的再活化。
A program of geochemical surveillance of the volcanic activity at Vulcano island (southern Italy) has allowed to collect a large set of observations, and the main chemical composition of volcanic gases is consequently known for the period from 1978 to 1993. This systematic monitoring with time of fumarolic activity at Vulcano has represented a good opportunity to investigate variations of arsenic concentrations in the condensates of fumarolic gases, and to correlate them both with temperature and chemical composition of the gases. Previous studies on arsenic behaviour in fumarolic gases for a similar long period are not reported in literature so far. Multivariate methodologies are a correct tool in order to investigate the simultaneous relationships between a large number of variables and to evaluate their changes with time. Since the chemical composition of volcanic gases is expressed by closed (or compositional) variables, the log-ratio approach has been adopted to overcome the induced correlations. By considering the results obtained by the application of Principal Component Analysis, the following considerations can be formulated: 1) arsenic behaviour appears to be mainly influenced by the presence of intense hydrothermal circulation as represented by the multivariate association of the element with variables as T, HF/H2O, NH3/H2O and H2S/H2O ratios; 2) the hydrothermal circulation, characterised by a continuous increase with time, appears as the main feature of the volcanic system; in this framework, the seismic event occurred in 1984 may have contributed to facilitate the fluid circulation; 3) no obvious relationships appear to link the increase of gas temperature with typical magmatic contributions as expressed by CO2/H2O and SO2/H2O ratios. The results indicate that the correlations between arsenic and the other physical-chemical parameters characterising the volcanic system are useful to constrain the interpretations on its geochemical evolution with time. This is particularly true if the system is dominated by hydrothermal processes as those of Vulcano island, where arsenic undergoes intensive remobilization.