Vapor‐Dominated Zones Within Hydrothermal Systems: Evolution and Natural State

Ingebritsen, Steven E.; Sorey, M.L.

doi:10.1029/jb093ib11p13635

Cited by 82 publications

(40 citation statements)

References 20 publications

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“…The system has a deep water table. This meteoric water "scrubs" (Symonds and others 2001) volcanic gases such as SO 2 , HF, and HCl and also serves as a source of H 2 S to overlying vadose or shallow vapor dominated zones as proposed by Ingebritsen and Sorey (1988). Gases in active fumaroles in summit cones contain spikes of CO 2 up to 10,000 ppm and traces of H 2 S but no SO 2 (Zimbelman and others, 2000).…”

Section: Mount Rainier Meteoric Water Hydrothermal Systemmentioning

confidence: 99%

Preliminary Mineralogic and Stable Isotope Studies of Altered Summit and Flank Rocks and Osceola Mudflow Deposits on Mount Rainier, Washington

Rye¹,

Breit²,

Zimbelman³

2003

Open-File Report

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About 5600 years ago part of Mount Rainier's edifice collapsed with the resultant Osceola Mudflow traveling more than 120 km and covering an area of at least 505 km 2 . Mineralogic and stable isotope studies were conducted on altered rocks from outcrops near the summit and east flank of the volcano and samples of clasts and matrix from the Osceola Mudflow. Results of these analyses are used to constrain processes responsible for pre-collapse alteration and provide insight into the role of alteration in edifice instability prior to the Osceola collapse event.Jarosite, pyrite, alunite, and kaolinite occur in hydrothermally altered rock exposed in summit scarps formed by edifice collapse events and in altered rock within the east-west structural zone (EWSZ) of the volcano's east flank. Deposits of the Osceola Mudflow contain clasts of variably altered and unaltered andesite within a clay-rich matrix. Minerals detected in samples from the edifice are also present in many of the clasts. The matrix includes abundant smectite, kaolinite and variably abundant jarosite.δ Hydrothermal fluid compositions calculated from hydrogen and oxygen isotope data of alunite, and smectite on Mount Rainier reflect mixing of magmatic and meteoric waters. The range in the δD values of modern meteoric water on the volcano (-85 to 155‰) reflect the influence of elevation on the δD of precipitation. The δ 34 S and δ 18 O SO4 values of alunite, gypsum and jarosite are distinct but together range from 1.7 to 17.6‰ and -12.3 to 15.0‰, respectively; both parameters increase from jarosite to gypsum to alunite. The variations in sulfur isotope composition are attributed to the varying contributions of disproportionation of magmatic SO 2 , the supergene oxidation of hydrothermal pyrite and possible oxidation of H 2 S to the parent aqueous sulfate. The 18 O SO4 values of jarosite are the lowest recorded for the mineral, consistent with a supergene origin.The mineralogy and isotope composition of alteration minerals define two and possibly three environments of alteration. At deeper levels magmatic vapor, H 2 S, SO 2 and other gases from venting magmas migrated upward and condensed into the meteoric water. Disproportionation of SO 2 into aqueous sulfate and H 2 S resulted in acid-sulfate (alunite + kaolinite + pyrite) and related argillic and propylitic alteration envelopes in a magmatic hydrothermal environment. At shallow levels H 2 S reacted with andesite to form pyrite that is associated with smectite along fractures on both the flanks and upper edifice. It is not clear to what extent H 2 S was oxidized by atmospheric O 2 to form aqueous sulfate in a steam-heated environment. Near the ground surface, pyrite is oxidized by atmospheric oxygen resulting in soluble iron-and aluminumhydroxysulfates. These supergene hydroxysulfates, which may also form around fumaroles from the oxidation of H 2 S, are subject to continuous solution and redeposition.

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Section: Mount Rainier Meteoric Water Hydrothermal Systemmentioning

confidence: 99%

Preliminary Mineralogic and Stable Isotope Studies of Altered Summit and Flank Rocks and Osceola Mudflow Deposits on Mount Rainier, Washington

Rye¹,

Breit²,

Zimbelman³

2003

Open-File Report

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“…In addition to the two types of two-phase hydrothermal systems discussed above, in some circumstances a parasitic vapor-dominated zone may develop within a liquiddominated system that has significant topographic relief [lngebritsen and Sorey, 1985Sorey, , 1988. A common feature of these systems is that steam and acid-sulfate springs discharge at relatively high altitudes and high-chloride springs discharge at lower altitudes, which is due to processes of boiling and phase separation possibly associated with a vapordominated zone within these systems.…”

Section: -0227/98/98jb-0148550900mentioning

confidence: 99%

An alternative model of the Lassen hydrothermal system, Lassen Volcanic National Park, California

Xu¹,

Lowell²

1998

J. Geophys. Res.

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Abstract. We describe an alternative two-dimensional numerical model for the Lassen hydrothermal system. As in earlier models, the new model consists of a vertical upflow zone with a low permeability caprock near its top and a permeable horizontal channel that connects to the upflow zone at depth. The new model, however, also includes a recirculation region beneath the horizontal channel and a recharge zone. Magmatic heating is explicitly represented by specifying heat flows near the bottom of the upflow zone. Simulations show that a periodically appearing vapor-dominated zone, which sometimes consists of pure-steam, develops beneath the caprock and feeds steam-type discharges at high elevations, while the horizontal channel feeds the hot-spring discharge region at lower elevations. This model is able to reproduce the inferred-1:1 discharge ratio between water and steam and to match estimates on current heat output from the system. The development of the vapor-dominated zone does not require dramatic changes in geohydrologic conditions. Our model also shows that both the vapor-dominated zone and the whole system evolve quasiperiodically with a period of-10 3 years. These oscillations are related to the unstable two-phase hydrothermal fluid flow. within the vapor-dominated zone. The observed high-frequency oscillations near the vapor-dominated zone superimposed on low frequency ones probably result from the osciliatory instability introduced by rapid changes in permeability of the low-permeability caprock. The results indicate that the system is probably still in a transient state.

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“…This model requires a high heat supply, which is provided at Yellowstone by the 5-to 17-km-deep magma (Farrell et al, 2014). In this model, a lowpermeability cap rock is an important component of the vapor-dominated system because it restricts the amount of recharge and thereby helps maintain the system (Ingebritsen and Sorey, 1988). Within the vapor-dominated reservoir, convective steam upflow is concentrated in the more permeable zones such as faults, and downflow of condensate occurs in smaller pores and fractures.…”

Section: The Yellowstone Hydrothermal Systemmentioning

confidence: 99%

Direct measurement of advective heat flux from several Yellowstone hot springs, Wyoming, USA

et al. 2018

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Actual measurements of advective heat flux from Yellowstone hot springs (Wyoming, USA) are seldom made, due to the difficulty of obtaining mass flow rates to support such measurements. Yet such measurements would provide important information that can be used to help evaluate the total thermal heat transport associated with the Yellowstone Caldera. Typically, discharge from thermal springs migrates through the shallow subsurface, making accurate measurement problematic. Here we present direct measurements of mass and thermal discharge from hot springs in the Lower Geyser Basin of Yellowstone National Park, USA. We added small amounts of nearly pure D 2 O to four springs in the Morning Mist Springs area that ranged in temperature from 74 to 95 °C and analyzed time-series dD samples to determine the volumes and discharge rates of the test springs. D 2 O was chosen to limit the ecological and/or visual impacts of other common tracers, such as NaCl or fluorescein dyes. We calculated spring volumes to range between 560 and 27,400 L and estimated mass and heat discharge as 0.08-1.25 L/s and 0.0189-0.312 MW, respectively. The volumes calculated by deuterium doping were larger in every case than those estimated by field inspection, suggesting that the volume participating in shallow fluid circulation is generally larger than is apparent from the surface. The heat flow data, when paired with conductive heat loss estimates in the vicinity of the springs, suggest that current estimates of thermal discharge at Yellowstone may underestimate heat loss from the caldera and offer insights on the rate of magma supplied by the mantle. Thermal flux estimates suggest that a minimum of 3.2-6.3 km 3 × 10 -2 of basalt magma enters the base of the crust annually.

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Vapor‐Dominated Zones Within Hydrothermal Systems: Evolution and Natural State

Cited by 82 publications

References 20 publications

Preliminary Mineralogic and Stable Isotope Studies of Altered Summit and Flank Rocks and Osceola Mudflow Deposits on Mount Rainier, Washington

Preliminary Mineralogic and Stable Isotope Studies of Altered Summit and Flank Rocks and Osceola Mudflow Deposits on Mount Rainier, Washington

An alternative model of the Lassen hydrothermal system, Lassen Volcanic National Park, California

Direct measurement of advective heat flux from several Yellowstone hot springs, Wyoming, USA

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