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首页> 外文期刊>Geosciences >A New Degassing Model to Infer Magma Dynamics from Radioactive Disequilibria in Volcanic Plumes
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A New Degassing Model to Infer Magma Dynamics from Radioactive Disequilibria in Volcanic Plumes

机译：一种新的脱气模型，从火山羽中的放射性不平衡现象推断岩浆动力学

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Mount Etna volcano (Sicily, Italy) is the place where short-lived radioactive disequilibrium measurements in volcanic gases were initiated more than 40 years ago. Almost two decades after the last measurements in Mount Etna plume, we carried out in 2015 a new survey of 210 Pb- 210 Bi- 210 Po radioactive disequilibria in gaseous emanations from the volcano. These new results [ ( 210 Po / 210 Pb ) = 42 and ( 210 Bi / 210 Pb ) = 7.5 ] are in fair agreement with those previously reported. Previously published degassing models fail to explain satisfactorily measured activity ratios. We present here a new degassing model, which accounts for 222 Rn enrichment in volcanic gases and its subsequent decay into 210 Pb within gas bubbles en route to the surface. Theoretical short-lived radioactive disequilibria in volcanic gases predicted by this new model differ from those produced by the former models and better match the values we measured in the plume during the 2015 campaign. A Monte Carlo-like simulation based on variable parameters characterising the degassing process (magma residence time in the degassing reservoir, gas transfer time, Rn-Pb-Bi-Po volatilities, magma volatile content) suggests that short-lived disequilibria in volcanic gases may be of use to infer both magma dynamics and degassing kinetics beneath Mount Etna, and in general at basaltic volcanoes. However, this simulation emphasizes the need for accurately determined input parameters in order to produce unambiguous results, allowing sharp characterisation of degassing processes.
机译：埃特纳火山（意大利西西里岛）是40多年前开始进行火山气体中短寿命放射性不平衡测量的地方。在埃特纳火山羽流的最后一次测量之后近二十年，我们于2015年对火山喷发的210 Pb- 210 Bi- 210 Po放射性失衡进行了新的调查。这些新结果[（210 Po / 210 Pb）= 42和（210 Bi / 210 Pb）= 7.5]与先前报道的结果相称。先前发布的脱气模型无法解释令人满意地测得的活性比。我们在这里提出了一种新的脱气模型，该模型解释了火山岩气体中222 Rn的富集及其随后在进入地面的气泡中衰减为210 Pb的原因。这个新模型预测的火山气体中理论上的短暂放射性失衡与以前的模型不同，并且更好地匹配了我们在2015年运动期间在羽流中测得的值。基于表征脱气过程的可变参数的类蒙特卡罗模拟（脱气储层中的岩浆停留时间，气体转移时间，Rn-Pb-Bi-Po挥发度，岩浆挥发物含量）表明，火山气体中的短暂失衡可能可用于推断埃特纳火山下的岩浆动力学和除气动力学，通常用于玄武岩火山。但是，此模拟强调需要精确确定的输入参数，以产生明确的结果，从而可以对脱气过程进行清晰的表征。

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