Geochemical monitoring of the 2002–2003 eruption at Stromboli volcano (Italy): precursory changes in the carbon and helium isotopic composition of fumarole gases and thermal waters
Geochemical monitoring of the 2002–2003 eruption at Stromboli volcano (Italy): precursory changes in the carbon and helium isotopic composition of fumarole gases and thermal waters
复制标题
2002-2003 年斯特龙博利火山（意大利）喷发的地球化学监测：喷气孔气体和热水的碳和氦同位素组成的前兆变化
DOI：
--
复制
发表时间：
2005
期刊：
影响因子：
--
通讯作者：
A. Rizzo
中科院分区：
文献类型：
--
作者：
G. Capasso;M. Carapezza;C. Federico;S. Inguaggiato;A. Rizzo
在2002年至2003年的喷发之前和期间，斯特龙博利记录了浅层热沃茨与气体和火山口火山气体的氦和碳同位素组成的显着变化。在2002年5月至11月期间，经空气污染校正后的3 He/4 He比值（Rc/Ra）和火山喷发气体的δ 13 C值逐渐升高。这些变化意味着早期脱气的气体丰富的岩浆在深度，可能美联储都强烈的斯特龙博利活动和小熔岩溢出记录在此期间。2002年12月下旬的熔岩喷发之前不久，水和火山气体中的Rc/Ra都显著下降。溶解气体中He/CO2和CH 4/CO2比值与$${
m delta }^{13} {
联系我们
m CO}_2 }$$值排除了由于放射性4 He输入增加而导致的Rc/Ra降低。Rc/Ra的降低是由于He同位素分馏过程中快速岩浆上升和脱气。2003年1月至2月可能发生了一次新的富3 He岩浆的上升，当时Rc/Ra比值显示了溶解气体中的最高值（4.56 Rc/Ra）。2003年4月5日爆发后，记录到He/CO2和CH 4/CO2比值的增加以及溶解CO2 δ 13 C的降低，可能是由于气水相互作用增强导致CO2溶解。没有异常Rc/Ra值记录在同一时期，当通常的Strombolian活动逐渐恢复。
Significant changes in the helium and carbon isotopic composition of shallow thermal waters vs. gas and a crater fumarolic gas have been recorded at Stromboli prior and during the 2002–2003 eruption. The3He/4He ratios corrected for air contamination (Rc/Ra), and δ13C of fumarolic gases gradually increased from May to November 2002 before the eruption onset. These variations imply early degassing of a gas-rich magma at depth that likely fed both the intense Strombolian activity and small lava overflows recorded during that period. The lava effusion of late December 2002 was shortly preceded by a marked Rc/Ra decrease both in water and fumarolic gases. Comparison of He/CO2 and CH4/CO2 ratios in dissolved gas and with$${
m delta }^{13} {
m C}_{{
m CO}_2 }$$ values rules out the Rc/Ra decrease due to an increasing input of radiogenic4He. The Rc/Ra decrease is attributed to the He isotope fractionation during rapid magma ascent and degassing. A new uprising of 3He-rich magma probably occurred in January to February 2003, when Rc/Ra ratios displayed the highest values in dissolved gases ever measured before (4.56 Rc/Ra). The increase in He/CO2 and CH4/CO2 ratios and decrease in δ13C of dissolved CO2 was recorded after the 5 April 2003 explosive paroxysm, likely caused by enhanced gas-water interaction inducing CO2 dissolution. No anomalous Rc/Ra values were recorded in the same period, when usual Strombolian activity gradually resumed.