Pre-eruption compositional gradients and mixing of andesite and dacite magma erupted from Nevado del Ruiz Volcano, Colombia in 1985

Sigurdsson, Haraldur; Carey, Steven; Palais, Julie M.; Devine, J. D.

doi:10.1016/0377-0273(90)90086-u

Cited by 51 publications

(29 citation statements)

References 30 publications

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“…In summary, the melt inclusion data indicate pre-eruptive water contents varying from 1.6 to 3.3 wt.%. These direct SIMS measurements are consistent with previous indirect estimates by Melson et al (1990) (1-4 wt.% H 2 O) and Sigurdsson et al (1990) (3-4 wt.% H 2 O).…”

Section: Water Contentssupporting

confidence: 91%

“…The presence of two magmas, and their macroscopic mixing, is supported by the pumice textures, some of which exhibit mingling features. Previous work also has documented the presence of two distinct magma compositions beneath Nevado del Ruiz, one andesitic and the other dacitic, with mixing and mingling between the two during the November 1985 eruption (Gourgaud & Thouret 1990;Melson et al 1990;Sigurdsson et al 1990).…”

Section: Major Element Abundances and Trendsmentioning

confidence: 91%

“…The great majority have silica contents higher than 70 wt.% on an anhydrous basis, and some glasses contain up to 77 wt.% SiO 2 . The rhyolitic compositions imply that the magma underwent significant amounts of crystallization and differentiation within a holding reservoir or reservoirs beneath the volcano (Sigurdsson et al 1990;Vatin-Pérignon et al 1990). These reservoirs are likely to be of small volume, considering the comparatively small amounts of magma that are erupted from this volcano during any single period of unrest.…”

Section: High-level Magmatic Processes At Nevado Del Ruizmentioning

confidence: 99%

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Mechanisms of degassing at Nevado del Ruiz volcano, Colombia

Stix

Layne

Williams

2003

JGS

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Nevado del Ruiz volcano is an andesite stratovolcano located in the northern Andes of Colombia. The volcano erupted on 11 September 1985, 13 November 1985, and 1 September 1989. The last two eruptions emitted juvenile solid material. This paper examines the volatile and light lithophile trace element contents of melt inclusions and matrix glasses from this juvenile material, and proposes a model for degassing within the volcano. Major element distributions in the glasses show two evolutionary trends, with subsidiary points that lie between the two trends. The data suggest the existence of two separate magmas, which have interacted, mingled, and mixed during their ascent and eruption. Water contents in melt inclusions, as determined by secondary ionization mass spectrometric analysis, are generally low, averaging between 1.6 and 3.3 wt.%. Halogen concentrations in the glasses range from 400 to 1200 ppm for fluorine and from 1100 to 1500 ppm for chlorine. Sulphur contents are low, not exceeding 500 ppm, with most glasses containing ,200 ppm. Lithium concentrations range from 20 to 40 ppm, beryllium from 1.5 to 2 ppm, and boron exhibits high variability from 30 to 100 ppm. The only significant difference between melt inclusions and matrix glasses is for water, with matrix glasses having significantly lower concentrations (,0.5 wt.%) than the melt inclusions. The generally elevated concentrations of boron in the magma may be a consequence of enrichment in the source region of the magma, i.e. by subduction of altered oceanic crust and/or sediments. Yet the large degree of boron heterogeneity in both melt inclusions and matrix glasses necessitates subsequent addition of boron at shallower depths as well, by the assimilation of crustal sedimentary rocks or by interaction with hydrothermal fluids. Evidence for pre-eruptive magma emplacement at shallow levels is provided by (1) anhydrous mineral assemblages of plagioclase and pyroxene, (2) high silica contents of glasses, and (3) low water contents in melt inclusions. When combined, these observations suggest a period of magma residence at shallow depths, probably ,3 km beneath the summit of the volcano. A multistage model of magma transport and degassing involves alternating periods of magma ascent and magma ponding. Initially, volatile-bearing magma ascends from depths of 9-15 km, driven by buoyancy. During decompression, the magma loses gas, particularly CO 2 and sulphur. The magma eventually ponds at its neutral buoyancy level. At this point, the gas-saturated magma cools and crystallizes, thereby liberating gas under isobaric conditions. As a result, CO 2 is depleted from the magma whereas H 2 O and SiO 2 are enriched. The H 2 O enrichment is caused by its increased solubility in the magma as CO 2 is degassed, whereas SiO 2 is enriched by fractional crystallization. The density of the magma decreases as the level of dissolved H 2 O increases, eventually causing the magma to become buoyant once more and to continue its ascent, either to erupt or to freeze a...

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Section: Water Contentssupporting

confidence: 91%

Section: Major Element Abundances and Trendsmentioning

confidence: 91%

Section: High-level Magmatic Processes At Nevado Del Ruizmentioning

confidence: 99%

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Mechanisms of degassing at Nevado del Ruiz volcano, Colombia

Stix

Layne

Williams

2003

JGS

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“…However, measured molar CO2/SO 2 ratios of volcanic emissions in convergent tectonic settings fall in the range 2-15 [Williams et al, 1992], and so for El Chich6n we assume a CO2/SO 2 ratio of 7. Additional constraints were XH20 = 0.95 for El Chich6n, as phase equilibria suggest [Luhr, 1990], and XH20=0.5 for Nevado del Ruiz because of the observed scarcity of amphibole in the eruptive products [Sigurdsson et al, 1990], which suggests pre eruption conditions on the verge of the stability field of amphibole. In both the Nevado del Ruiz and Redoubt eruptions there is petrologic evidence for magma mixing before eruption [Sigurdsson et al, 1990; Goutgaud and Thouret, 1990; Swanson et al, 1994], and glass sulfur contents are highly variable with the lowest sulfur contents in the most silicic glasses [Sigurdsson et al, 1990;.…”

mentioning

confidence: 99%

Redox control of sulfur degassing in silicic magmas

Scaillet¹,

Clemente²,

Evans³

et al. 1998

J. Geophys. Res.

191

139

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Abstract. Explosive eruptions involve mainly silicic magmas in which sulfur solubility and diffusivity are low. This inhibits sulfur exsolution during magma uprise as compared to more mafic magmas such as basalts. Silicic magmas can nevertheless liberate large quantities of sulfur as shown by the monitoring of SO2 in recent explosive silicic eruptions in arc settings, which invariably have displayed an excess of sulfur relative to that calculated from melt degassing. If this excess sulfur is stored in a fluid phase, it implies a strong preference of sulfur for the fluid over the melt under oxidized conditions, with fluid/melt partition coefficients varying between 50 and 2612, depending on melt composition. Experimentally determined sulfur partition coefficients for a dacite bulk composition confirm this trend and show that in volcanic eruptions displaying excess gaseous sulfur, the magmas were probably fluid-saturated at depth. The experiments show that in more reduced silicic magmas, those coexisting only with pyrrhotite, the partition coefficient decreases dramatically to values around 1, because pyrrhotite locks up nearly all the sulfur of the magma. Reevaluation of the sulfur yields of some major historical eruptions in the light of these results shows that for oxidized magmas, the presence of 1-5 wt % fluid may indeed account for the differences observed between the petrologic estimate of the sulfur yield and that constrained from ice core data. Explosive eruptions of very large magnitude but involving reduced and cool silicic magmas, such as the Toba or the Bishop events, release only minor amounts of sulfur and could have consequently negligible long-term (years to centuries) atmospherical effects. This redox control on sulfur release diminishes as the melt composition becomes less silicic and as temperature increases, because both factors favor more efficient melt sulfur degassing owing to the increased diffusivity of sulfur in silicate melts under such conditions.

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“…34), (DEVINE et al, 1984;SIGURDSSON et al, 1985;METRICH & CLOG-CHIATTI 1989;PAI.AIS & SIGURDSSON 1989), eine Methode, die auch f/ir AbscMtzungen des Schwefelausstot~es bei der 11 000 Jahre alten Laacher-See-Eruption angewendet wurde (ScHMINCKE et al, 1990;BOCAARD et al, 1990 ANDRES et al, 1991). Nur etwa 10 % der emittierten SO2-Mengen der Eruption des E1 Chich6n im Jahre 1982 und des Nevado del Ruiz in 1985 lassen sich durch Entgasung des eruptierten Magmas erkl~iren (LUHR et al, 1984;SIGURDSSON et al, 1990). Auch bei der Eruption des Pinatubo war die Diskrepanz zwischen emittierten SO2-Mengen und der maximal im Magma 16slichen sehr grof~ (BA-KER & RUTHERFORD 1992;McKIBBEN et al, 1992 (CASTLEMAN et al, 1974;TURCO et al, 1982;HOFMANN & ROSEN 1983;SNETSINGER et al, 1987;MICHELANGELI et al, 1989) (LABITZKE et al, 1983;GELMANN 1992;SIMARSKI 1992 …”

Section: So2unclassified

Transfer von festen, flüssigen und gasförmigen Stoffen aus Vulkanen in die Atmosphäre

Schmincke¹

1993

UWSF - Z Umweltchem Ökotox

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Zusammenfassung. Die hfiufigsten vulkanischen Volatilen sind H20 , CO2, SO 3 und Halogene. Zusammensetzung, Menge und Injektionsraten von vulkanischen Gasen und Partikeln in die Troposphere und Stratosph~ire h/ingen ab yon der chemischen Zusammensetzung eines Magmas, dem plattentektonischen Milieu sowie Eruptionsmechanismen und Eruptionsraten. l[lber 90 % der eruptierten Magmen sind basaltischer Zusammensetzung mit niedriger Viskositfit, relativ geringen Volatilengehalten und meist niedrigen Eruptionsraten sowie wenig explosiven Eruptionen fiberwiegend entlang der mittelozeanischen Riicken in grot~en Wassertiefen. Magmen in Inselbfgen und Subduktionszonen an Kontinentrfindern sind H20-reich , in anderen plattentektonischen Milieus tiberwiegt in basaltischen Magmen CO 2. In mafischen Magmen ist CO 2 schlecht 16slich und kann daher schon mehrere Kilometer unter der Erdoberfl/iche als Gasphase aus einem Magma entweichen. Felsische (hochdifferenzierte) Magmen, H20-reich und CO2-arm , eruptieren oft hochexplosiv, insbesondere an Subduktionszonen, und mit hohen Eruptionsraten, z.B. E1 Chich6n (Mexiko, 1982) und Pinatubo (Philippinen, 1991. lhre Eruptionss~iulen (Gas-/Partikelgemische) k6nnen bis ca. 40 km H6he erreichen und sind Hauptlieferant der in die Stratusph~ire injizierten Gasmengen.

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Pre-eruption compositional gradients and mixing of andesite and dacite magma erupted from Nevado del Ruiz Volcano, Colombia in 1985

Cited by 51 publications

References 30 publications

Mechanisms of degassing at Nevado del Ruiz volcano, Colombia

Mechanisms of degassing at Nevado del Ruiz volcano, Colombia

Redox control of sulfur degassing in silicic magmas

Transfer von festen, flüssigen und gasförmigen Stoffen aus Vulkanen in die Atmosphäre

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