TY - JOUR

T1 - Partitioning of Cl and F between fluid and hydrous phonolitic melt of Mt. Vesuvius at ~ 850-1000 °C and 200 MPa

AU - Yu. Chevychelov, Vitaliy

AU - Botcharnikov, Roman E.

AU - Holtz, Francois

N1 - Funding Information: The authors are grateful to H. Behrens for assistance during experimental studies and the discussion of obtained results. We thank O. Diedrich and S. Schoenborn for the help with sample preparation and electron microprobe analyses, respectively. B. Scaillet and D. Dolejs are acknowledged for the very useful comments that improved the quality of the paper. Financial support was provided by the German Science Foundation (Ho 1337/8), the German Academic Exchange Service (DAAD study grant), Russian Foundation for Basic Research (Grant No.05-05-64754) and Scientific School (Grant No. NSh-3763.2008.5). Copyright: Copyright 2018 Elsevier B.V., All rights reserved.

PY - 2008/11/15

Y1 - 2008/11/15

N2 - The solubilities of Cl- and/or F-bearing fluids in phonolitic melts of Vesuvius volcano have been determined experimentally at temperatures of 845-865 °C and 1000 °C, and pressure of 200 MPa. At 845-865 °C, the maximum Cl concentration in the melt (mCl) coexisting with Cl-rich (~ 35.5 wt.%; flCl) and F-free fluid is about 0.5 wt.%. An addition of F to the system increases the Cl content of the melt up to 0.7 wt.% at ~ 39 wt.% Cl and ~ 13 wt.% F in the fluid(s). The relationship between mCl and flCl indicates that low-density vapor and dense brine phases might have coexisted in some experiments. The relationship between mCl and flCl at 1000 °C is similar to that determined at 845-865 °C, implying that variations of temperature in the range 850-1000 °C have no significant effect on the partitioning of Cl between fluid and phonolitic melt. The concentration of F in phonolitic melt coexisting with F-rich fluid(s) reaches at least 0.9 wt.% at 845-865 °C and 1.3 wt.% at 1000 °C. The comparison of data from experiments conducted in Au and Pt capsules indicates that F may react with Au, which influences the quality of the experimental results. The partition coefficients of F between bulk fluid and melt (fl/mDF) are higher than 1 in all experiments, indicating that fluorine is preferentially incorporated into the fluid phase in phonolitic systems, in contrast to fl/mDF values determined in rhyolitic systems. The influence of Cl on fl/mDF is not detectable at the conditions of our experiments. The experimental data imply that Mt. Somma-Vesuvius phonolitic magmas from the eruptions between A.D. 79 and A.D. 1944 may have coexisted with Cl-rich and F-rich fluid phase(s) prior to eruption.

AB - The solubilities of Cl- and/or F-bearing fluids in phonolitic melts of Vesuvius volcano have been determined experimentally at temperatures of 845-865 °C and 1000 °C, and pressure of 200 MPa. At 845-865 °C, the maximum Cl concentration in the melt (mCl) coexisting with Cl-rich (~ 35.5 wt.%; flCl) and F-free fluid is about 0.5 wt.%. An addition of F to the system increases the Cl content of the melt up to 0.7 wt.% at ~ 39 wt.% Cl and ~ 13 wt.% F in the fluid(s). The relationship between mCl and flCl indicates that low-density vapor and dense brine phases might have coexisted in some experiments. The relationship between mCl and flCl at 1000 °C is similar to that determined at 845-865 °C, implying that variations of temperature in the range 850-1000 °C have no significant effect on the partitioning of Cl between fluid and phonolitic melt. The concentration of F in phonolitic melt coexisting with F-rich fluid(s) reaches at least 0.9 wt.% at 845-865 °C and 1.3 wt.% at 1000 °C. The comparison of data from experiments conducted in Au and Pt capsules indicates that F may react with Au, which influences the quality of the experimental results. The partition coefficients of F between bulk fluid and melt (fl/mDF) are higher than 1 in all experiments, indicating that fluorine is preferentially incorporated into the fluid phase in phonolitic systems, in contrast to fl/mDF values determined in rhyolitic systems. The influence of Cl on fl/mDF is not detectable at the conditions of our experiments. The experimental data imply that Mt. Somma-Vesuvius phonolitic magmas from the eruptions between A.D. 79 and A.D. 1944 may have coexisted with Cl-rich and F-rich fluid phase(s) prior to eruption.

KW - Chlorine

KW - Fluorine

KW - Mixed fluid

KW - Partitioning

KW - Phonolitic melt

KW - Vesuvius volcano

UR - http://www.scopus.com/inward/record.url?scp=54449083343&partnerID=8YFLogxK

U2 - 10.1016/j.chemgeo.2008.06.025

DO - 10.1016/j.chemgeo.2008.06.025

M3 - Article

AN - SCOPUS:54449083343

VL - 256

SP - 172

EP - 184

JO - Chemical Geology

JF - Chemical Geology

SN - 0009-2541

IS - 3-4

ER -