A model for the magmatic–hydrothermal system at Mount Rainier, Washington, from seismic and geochemical observations

Moran, S. C.; Zimbelman, David R.; Malone, Stephen D.

doi:10.1007/pl00008909

Cited by 43 publications

(30 citation statements)

References 23 publications

(37 reference statements)

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“…Rubin and Gillard, 1998); the inflation of the magmatic reservoir, which increases stress, producing rock failure or reactivating pre-existing faults (e.g. Feigl et al, 2000) and gravitational loading of the volcanic edifice (Moran et al, 2000). Dike emplacement as the source of the volcanotectonic events recorded to date on Fogo is ruled out because, for example, the rate is very low (only one event every two months), much below the normal rate in dike-related processes (e.g.…”

Section: Fogomentioning

confidence: 99%

Investigating volcanic hazard in Cape Verde Islands through geophysical monitoring: network description and first results

Faria¹,

Fonseca²

2014

Nat. Hazards Earth Syst. Sci.

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Abstract. We describe a new geophysical network deployed in the Cape Verde Archipelago for the assessment and monitoring of volcanic hazards as well as the first results from the network. Across the archipelago, the ages of volcanic activity range from ca. 20 Ma to present. In general, older islands are in the east and younger ones are in the west, but there is no clear age progression of eruptive activity as widely separated islands have erupted contemporaneously on geological timescales. The overall magmatic rate is low, and there are indications that eruptive activity is episodic, with intervals between episodes of intense activity ranging from 1 to 4 Ma. Although only Fogo Island has experienced eruptions (mainly effusive) in the historic period (last 550 yr), Brava and Santo Antão have experienced numerous geologically recent eruptions, including violent explosive eruptions, and show felt seismic activity and geothermal activity. Evidence for recent volcanism in the other islands is more limited and the emphasis has therefore been on monitoring of the three critical islands of Fogo, Brava and Santo Antão, where volcanic hazard levels are highest. Geophysical monitoring of all three islands is now in operation. The first results show that on Fogo, the seismic activity is dominated by hydrothermal events and volcano-tectonic events that may be related to settling of the edifice after the 1995 eruption; in Brava by volcano-tectonic events (mostly offshore), and in Santo Antão by volcano-tectonic events, medium-frequency events and harmonic tremor. Both in Brava and in Santo Antão, the recorded seismicity indicates that relatively shallow magmatic systems are present and causing deformation of the edifices that may include episodes of dike intrusion.

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Section: Fogomentioning

confidence: 99%

Investigating volcanic hazard in Cape Verde Islands through geophysical monitoring: network description and first results

Faria¹,

Fonseca²

2014

Nat. Hazards Earth Syst. Sci.

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“…1, inset). The volcanoes can be grouped by: (1) their seismicity, with relatively low levels at Mount Adams and Mount Shasta and more moderate levels at Citlaltépetl, Mount Hood, and Mount Rainier (Clarke and Carver, 1992;Stanley et al, 1996;Moran et al, 2000), and (2) the presence or lack of domes, with Citlaltépetl, Mount Hood, and Mount Shasta containing abundant domes and Mount Adams and Mount Rainier generally lacking domes. All of these volcanoes contain ice caps on their upper slopes, exposed hydrothermally altered sulfate-bearing rock, active fumaroles, and have undergone edifice collapse.…”

Section: Volcano Descriptionsmentioning

confidence: 99%

Origin of secondary sulfate minerals on active andesitic stratovolcanoes

Zimbelman¹,

2005

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Sulfate minerals in altered rocks on the upper flanks and summits of active andesitic stratovolcanoes result from multiple processes. The origin of these sulfates at five active volcanoes, Citlaltépetl (Mexico), and Mount Adams, Hood, Rainier, and Shasta (Cascade Range, USA), was investigated using field observations, petrography, mineralogy, chemical modeling, and stable-isotope data. The four general groups of sulfate minerals identified are: (1) alunite group, (2) jarosite group, (3) readily soluble Fe-and Al-hydroxysulfates, and (4) simple alkaline-earth sulfates such as anhydrite, gypsum, and barite. Generalized assemblages of spatially associated secondary minerals were recognized: (1) alunite+silicaFpyriteFkaoliniteFgypsumFsulfur, (2) jarosite+alunite+silica; (3) jarosite+smectite+silicaFpyrite, (4) Fe-and Al-hydroxysulfates+silica, and (5) simple sulfates+silicaFAl-hydroxysulfatesFalunite.Isotopic data verify that all sulfate and sulfide minerals and their associated alteration assemblages result largely from the introduction of sulfur-bearing magmatic gases into meteoric water in the upper levels of the volcanoes. The sulfur and oxygen isotopic data for all minerals indicate the general mixing of aqueous sulfate derived from deep (largely disproportionation of SO 2 in magmatic vapor) and shallow (oxidation of pyrite or H 2 S) sources. The hydrogen and oxygen isotopic data of alunite indicate the mixing of magmatic and meteoric fluids. Some alunite-group minerals, along with kaolinite, formed from sulfuric acid created by the disproportionation of SO 2 in a condensing magmatic vapor. Such alunite, observed only in those volcanoes whose interiors are exposed by erosion or edifice collapse, may have d 34 S values that reflect equilibrium (350F50 8C) between aqueous sulfate and H 2 S. Alunite with d34 S values indicating disequilibrium between parent aqueous sulfate and H 2 S may form from aqueous sulfate created in higher level low-temperature environments in which SO 2 is scrubbed out by groundwater or where H 2 S is oxidized. Jarosite-group minerals associated with smectite in only slightly altered volcanic rock are formed largely from aqueous sulfate derived from supergene oxidation of hydrothermal pyrite above the water table. Soluble Al-and Fehydroxysulfates form in low-pH surface environments, especially around fumaroles, and from the oxidation of hydrothermal pyrite. Anhydrite/gypsum, often associated with native sulfur and occasionally with small amounts of barite, also commonly form around fumaroles. Some occurrences of anhydrite/gypsum may be secondary, derived from the dissolution and reprecipitation of soluble sulfate. Edifice collapse may also reveal deep veins of anhydrite/gypsumFbarite that formed from the mixing of saline fluids with magmatic sulfate and dilute meteoric water. Alteration along structures associated with both 0009-2541/$ -see front matter D

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“…2. Fluid circulation reduces the yield strength of the country rock by the alteration of rock to secondary minerals, including clays, thus reducing the shear stress required to initiate fracturing (geochemical weakening;NISHI et al, 1996;MORAN et al, 2000). 3.…”

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confidence: 99%

Multiparametric Approach in Investigating Volcano-Hydrothermal Systems: the Case Study of Vulcano (Aeolian Islands, Italy)

Cannata

Diliberto

Alparone

et al. 2011

Pure Appl. Geophys.

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Seismic activity, ground deformation, and soil and fumarole temperatures acquired during 2004-2007 at Vulcano (Aeolian Islands) are analysed and the time relations among the different time series are discussed. Changes in temperature of fumarolic gases took place during four ''anomalous'' periods () at the same time as an increasing number of volcano-seismic events. In particular, the temperatures at high temperature vents and at steam heated soil ranged in time from 180 to 440°C and from 20 to 90°C, respectively. The maximum daily number of volcano-seismic events was 57, reached during the second anomalous period. This seismicity, characterised by focal depth generally lower than 1 km below sea level (b.s.l.) and composed of different kinds of events associated to both resonance and shear failure processes, is related to the shallow dynamics of the hydrothermal system. During the analysed period, very few volcano-tectonic earthquakes took place and tilt recordings showed no sharp or important changes. In light of such observations, the increases in both temperature and volcano-seismic events number were associated to increases in the release of gas from a deep and stable magma body, without magma intrusions within the shallow hydrothermal system. Indeed, a greater release of gas from depth leads to increased fluid circulation, that can promote increases in volcano-seismic events number by both fracturing processes and resonance and vibration in cracks and conduits. The different trends observed in the measured geochemical and geophysical series during the anomalous periods can be due to either time changes in the medium permeability or a changing speed of gas release from a deep magma body. Finally, all the observed variations, together with the changing temporal distribution of the different seismic event kinds, suggest that the hydrothermal system at Vulcano can be considered unsteady and dynamic.

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A model for the magmatic–hydrothermal system at Mount Rainier, Washington, from seismic and geochemical observations

Cited by 43 publications

References 23 publications

Investigating volcanic hazard in Cape Verde Islands through geophysical monitoring: network description and first results

Investigating volcanic hazard in Cape Verde Islands through geophysical monitoring: network description and first results

Origin of secondary sulfate minerals on active andesitic stratovolcanoes

Multiparametric Approach in Investigating Volcano-Hydrothermal Systems: the Case Study of Vulcano (Aeolian Islands, Italy)

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