Spectroscopic observation of HCl degassing from Soufriere Hills Volcano, Montserrat

Oppenheimer, Clive; Francis, P. W.; Maciejewski, Adam

doi:10.1029/98gl01584

Cited by 32 publications

(18 citation statements)

References 14 publications

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“…5). This amount is significantly lower than that observed by open-path infrared measurements (15 kg s ±1 ; Oppenheimer et al 1998) and by direct sampling of high temperature gas (10 kg s ±1 ; Hammouya et al 1998) during a period (February to August 1996) of rapid increase (4±10 m 3 s ±1 ) in dome extrusion rate (Young et al 1998a); however, if the abundant crystallization of plagioclase microlites during magma ascent is taken into account, D Cl has to increase passing from 0.049 wt.% (stage 1; no microlites formed) to 0.084 wt.% (stage 3, with 50% extra microlites; i.e. half of groundmass crystallized; see Fig.…”

Section: Variation Of CL Solubility In Experimental Glassescontrasting

confidence: 70%

“…High Cl emissions from the volcano were also indicated by measurements of HCl fluxes (>15 kg s ±1 or 1300 t day ±1 ) using open-path Fourier transform infrared spectroscopy (OP-FTIR) during July to August 1996 (Oppenheimer et al 1998). Such high Cl emissions are rare for andesitic magma eruptions and arc volcanoes more typically display HCl emissions of 10,000 mol/mol (Symonds et al 1994, and references therein).…”

Section: Introductionmentioning

confidence: 98%

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Experimental constraints on the origin of chlorine emissions at the Soufrière Hills volcano, Montserrat

Signorelli

Carroll

2001

Bull Volcanol

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Experimental study of Cl solubility in a rhyolitic melt composition corresponding to the phenocryst-free matrix of the recently erupted Soufrire Hills andesite provides insights into the origin of Cl emitted to the atmosphere during the eruption. The experiments were done at 25±250 MPa, 860±890 C, and they involved equilibration of the estimated matrix composition [~71 wt.% SiO 2 , molar (Na 2 O+ K 2 O)/Al 2 O 3~0 .6] with a Cl-rich aqueous fluid or aqueous fluid+hydrosaline brine. The Cl concentrations in glasses from the experimental run products (0.48±0.68 wt.% Cl) are significantly higher than those observed in natural matrix glasses (~0.20 wt.% Cl) and melt inclusions (0.300.07 wt.% Cl). These results indicate that if the pre-eruptive Montserrat magma was vapour saturated, the vapour phase would have been Cl poor and there was not a co-existing hydrosaline brine. This interpretation, based on Cl solubility data, is supported by the observed coincidence between remote sensing measurements of Cl emissions (as HCl) and petrological estimates of Cl emissions based on the volume of magma extruded and Cl contents of melt inclusions and matrix glasses (with correction for groundmass crystallization during ascent). The Cl emissions during the Soufrire Hills eruption are thus proposed to simply reflect syn-eruptive degassing of magma during ascent.

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Section: Variation Of CL Solubility In Experimental Glassescontrasting

confidence: 70%

Section: Introductionmentioning

confidence: 98%

Experimental constraints on the origin of chlorine emissions at the Soufrière Hills volcano, Montserrat

Signorelli

Carroll

2001

Bull Volcanol

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“…Sigvaldason 1974;Shinohara et al 1993;Francis et al 1995). Enhanced volatilisation of HCl from entrained seawater might help to explain these observations, which are further supported by the COSPEC and FTIR measurements of Oppenheimer et al (1998) and Young et al (1998b), which suggested average daily fluxes from Soufrière Hills of 200 tonnes of SO 2 and 3000 tonnes of HCl, the latter approximately twice the value calculated for Mount Etna (Francis et al 1995).…”

Section: Meteorologymentioning

confidence: 54%

Gas and particle emissions from Soufrière Hills Volcano, Montserrat, West Indies: characterization and health hazard assessment

Allen¹,

Baxter

Ottley

2000

Bulletin of Volcanology

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The Soufrière Hills Volcano, Montserrat, erupting since 18 July 1995, intensified its degassing in early 1996 with the continuing growth of the lava dome inside the summit crater. During this period of increased activity, between 11 and 18 March 1996, we measured gases and particles within the visible plume to determine whether at that time it posed a health risk to the population of Plymouth, the capital town, which is 5 km southwest (downwind) and was then still occupied. Gravimetric measurements were made of total suspended particles (TSP) and particles having an aerodynamic diameter of less than 10 mm (PM 10 ). Measurements were made of sulphur dioxide (SO 2 ), hydrochloric acid (HCl), hydrofluoric acid (HF), nitric acid (HNO 3 ), acetic acid (CH 3 COOH), formic acid (HCOOH), and particulate sulphate (SO 4 2-), chloride (Cl -), nitrate (NO 3 -), fluoride (F -), methanesulphonate (CH 3 SO 3 -), acetate (CH 3 COO -), formate (HCOO -), ammonium (NH 4 c ), sodium (Na c ) and acidity (H c ). Trace metals having human health implications [chromium (Cr), nickel (Ni), cobalt (Co), copper (Cu), zinc (Zn), arsenic (As), selenium (Se), cadmium (Cd), tin (Sn), mercury (Hg) and lead (Pb)] were also determined. Mean concentrations of HCl, SO 2 and HF obtained in the town of Plymouth were 14.0, 5.9 and 0.8 ppbv, respectively. Corresponding concentrations in the mixed plume on the crater edge were 533, 168 and 22 ppbv. There were no direct emissions of HNO 3 , although nitrate was detected in coarse particles at the source. Higher concentrations of CH 3 COOH and HCOOH were measured close to the crater. Mean TSP and PM 10 were 64 and 15 mg m -3 in Plymouth, and 455 and 47 mg m -3 on the upper volcano slope. Aerosols were highly acidic at the source but rapidly neutralised during transport. Trace metals were enriched in the aerosol relative to crater surface material. The concentrations of the acid gases, sulphur dioxide in particular, and particles were found to be too small to pose a health hazard at the time of these measurements, when relatively modest volcanic activity was occurring.

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“…The raw spectra are analysed for HCl and SO 2 using a forward model. A more detailed description of data reduction procedures may be found elsewhere Oppenheimer et al 1998).…”

Section: Methodsmentioning

confidence: 99%

HCl emissions at Soufrière Hills Volcano, Montserrat, West Indies, during a second phase of dome building: November 1999 to October 2000

2001

Self Cite

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HCl:SO 2 mass ratios measured by open path Fourier transform spectroscopy (OP-FTIR) in the volcanic plume at Soufrière Hills Volcano, Montserrat, are presented for the second phase of dome building between November 1999 and November 2000. HCl:SO 2 mass ratios of greater than 1 and HCl emission rates of greater than 400 t day -1 characterise periods of dome building for this volcano. The data suggest that chlorine partitions into a fluid phase as the magma decompresses and exsolves water during ascent. This is substantiated by a correlation between chlorine and water content in the melt (derived from the geochemical analysis of plagioclase melt inclusion and matrix glasses from phase I and II of dome growth). The matrix glass from the November 1999 and March 2000 domes indicate an open system degassing regime with a fluid-melt partition coefficient for chlorine of the order of 250-300. September 1997 glasses have higher chlorine contents and may indicate a switch to closed system degassing prior to explosive activity in September and October 1997. The OP-FTIR HCl time series suggests that HCl emission rate is strongly related to changes in eruption rate and we infer an emission rate of over 13.5 kt day -1 HCl during a period of high extrusion rate in September 2000. A calculation of the HCl emission rate expected for varying extrusion rates from the open-system degassing model suggests a HCl emission rate of the order of 1-4 kt day -1 is indicative of an extrusion rate of between 2 and 8 m 3 s -1 . Monitoring of HCl at Soufrière Hills Volcano provide a proxy for extrusion rate, with changes in ratio between HCl and SO 2 occurring rapidly in the plume. Order of magnitude changes occur in HCl emission rates over the time-scale of hours to days, making these changes easy to detect during the day-to-day monitoring of the volcano. Mean water emission rates are calculated to range from 9-24 kt day -1 during dome building activity, calculated from the predicted mass ratio of H 2 O:HCl in the fluid at the surface and FTIR-derived HCl emission rates.

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Spectroscopic observation of HCl degassing from Soufriere Hills Volcano, Montserrat

Cited by 32 publications

References 14 publications

Experimental constraints on the origin of chlorine emissions at the Soufrière Hills volcano, Montserrat

Experimental constraints on the origin of chlorine emissions at the Soufrière Hills volcano, Montserrat

Gas and particle emissions from Soufrière Hills Volcano, Montserrat, West Indies: characterization and health hazard assessment

HCl emissions at Soufrière Hills Volcano, Montserrat, West Indies, during a second phase of dome building: November 1999 to October 2000

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