Variations of Cl, F, and S in mount Etna's plume, Italy, between 1992 and 1995

Abstract. This study investigatedsa tao n the C1,F , and S concentrationosf plume-filters amples collectedb etween1 992a nd 1995f romM ountE tna.T he samplesw erec ollectedd uringe ruptive andn oneruptivea ctivity and showf airly constanCt 1/Fr atiosb ut wide variationi n the C1/Sr atios. The determinatio onf the C1/Fr atio( between5 and 14) allowsa n estimateo f F degassintgo be derivedt hat rangesf rom 10 to 30% of the initial F contento f the magma.T he variationi n the C1/Sr atio fits an empiricalt wo-staged egassingm odelw hereg asw ith high C1/Sr atio is discharged uringq uiesciendt egassingan dg asw ith low C1/Sr atiosi s discharged uringe ruptive degassingT.h e typicalp ermanendt egassinogc cursfr om a deptha t whichc hlorinee exsoluti on exceedss ulfure xsolution(C 1/S>1 ). The oppositeo f thisb ehavioris observed duringe ruptive periodsw hens ignificanst ulfurd egassinogc cursb ecausme agmad egasseast neara tmospheric pressure(C 1/SN0.1)T. he C1/Sr atio in the plume,characterizintgh e type of degassingh,a st he potentialt o be a usefulg eochemicatlo ol for monitoringth e volcano.