The Lassen geothermal system

Muffler, L. J. Patrick; Nehring, N.L.; Truesdell, A.H.; Janik, C.J.; Clynne, Michael A.; Thompson, J. M. T.

doi:10.3133/ofr82926

Cited by 17 publications

(18 citation statements)

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“…This temperature is suggested by liquid geothermometry at the high-chloride vents and by gas geothermometry at both the acidsulfate and high-chloride vents (Muffler et al 1982;Thompson 1985;Janik and McLaren 2010). Furthermore, the stable-isotope composition (dD and d 18 O) of samples from the acid-sulfate and high-chloride vents is consistent with phase separation at ~240 °C (Muffler et al 1982;Ingebritsen and Sorey 1985;Janik and McLaren 2010).…”

Section: Steam Up Owsupporting

confidence: 62%

“…Furthermore, the stable-isotope composition (dD and d 18 O) of samples from the acid-sulfate and high-chloride vents is consistent with phase separation at ~240 °C (Muffler et al 1982;Ingebritsen and Sorey 1985;Janik and McLaren 2010). There is no geochemical evidence that the circulating hydrothermal fluids ever attain temperatures significantly in excess of 240 °C.…”

Section: Steam Up Owsupporting

confidence: 55%

“…Stable-isotope compositions (dD and d 18 O) of Lassen hydrothermal fluids suggest that they originate as local meteoric recharge on the Lassen highlands (Muffler et al 1982;Ingebritsen and Sorey 1985;Janik and McLaren 2010). Patterns of seismicity (Fig.…”

Section: Patterns Of Hydrothermal Circulationmentioning

confidence: 98%

“…Early studies (e.g., Muffler et al 1982;Ingebritsen and Sorey 1985) invoked a single upflow zone beneath Bumpass Hell; a hydraulically well-connected liquid-dominated system with parasitic vapor-dominated zones. Janik and McLaren (2010) proposed an alternative model that involves two separate hydrothermal fluid cells rather than a single, connected system.…”

Section: Patterns Of Hydrothermal Circulationmentioning

confidence: 99%

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The Lassen hydrothermal system

Ingebritsen

Bergfeld

Clor

et al. 2016

American Mineralogist

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The active Lassen hydrothermal system includes a central vapor-dominated zone or zones beneath the Lassen highlands underlain by ~240 °C high-chloride waters that discharge at lower elevations. It is the best-exposed and largest hydrothermal system in the Cascade Range, discharging 41 ± 10 kg/s of steam (~115 MW) and 23 ± 2 kg/s of high-chloride waters (~27 MW). The Lassen system accounts for a full 1/3 of the total high-temperature hydrothermal heat discharge in the U.S. Cascades (140/400 MW). Hydrothermal heat discharge of ~140 MW can be supported by crystallization and cooling of silicic magma at a rate of ~2400 km 3 /Ma, and the ongoing rates of heat and magmatic CO 2 discharge are broadly consistent with a petrologic model for basalt-driven magmatic evolution. The clustering of observed seismicity at ~4-5 km depth may define zones of thermal cracking where the hydrothermal system mines heat from near-plastic rock. If so, the combined areal extent of the primary heat-transfer zones is ~5 km 2 , the average conductive heat flux over that area is >25 W/m 2 , and the conductive-boundary length <50 m. Observational records of hydrothermal discharge are likely too short to document long-term transients, whether they are intrinsic to the system or owe to various geologic events such as the eruption of Lassen Peak at 27 ka, deglaciation beginning ~18 ka, the eruptions of Chaos Crags at 1.1 ka, or the minor 1914-1917 eruption at the summit of Lassen Peak. However, there is a rich record of intermittent hydrothermal measurement over the past several decades and more-frequent measurement 2009-present. These data reveal sensitivity to climate and weather conditions, seasonal variability that owes to interaction with the shallow hydrologic system, and a transient 1.5-to twofold increase in high-chloride discharge in response to an earthquake swarm in mid-November 2014.

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Section: Steam Up Owsupporting

confidence: 62%

Section: Steam Up Owsupporting

confidence: 55%

Section: Patterns Of Hydrothermal Circulationmentioning

confidence: 98%

Section: Patterns Of Hydrothermal Circulationmentioning

confidence: 99%

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The Lassen hydrothermal system

Ingebritsen

Bergfeld

Clor

et al. 2016

American Mineralogist

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“…However, waters in acid-hot springs and solfataras (i.e., at Lassen, California and Yellowstone, Wyoming) typically show an enrichment in both deuterium and oxygen relative to the initial meteoric water composition. This enrichment is due to non-equilibrium surface evaporation of steam at temperatures of about 70-100°C and the composition of the waters plot about a line of slope 3 (Craig, 1963;Muffler et al 1982;Truesdell and Hulston, 1980). A line of this slope originating from the point of present-day ground waters (5D = -30 to-40%o) falls on the composition field of fluids responsible for steam-heated alteration at Rodalquilar (Fig.…”

Section: Stable Isotope Geochemistrymentioning

confidence: 95%

Preliminary study of the ore deposits and hydrothermal alteration in the Rodalquilar caldera complex, southeastern Spain

Arribas¹,

Rytuba²,

Rye³

et al. 1989

Open-File Report

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SUMMARYThe Rodalquilar gold-alunite deposits are the first documented example of calderarelated epithermal gold mineralization in Europe. Mineralization occurs in rhyolitic tuffs and domes of the Rodalquilar caldera complex in the Miocene Cabo de Gata volcanic field. Geologic constraints indicate a close temporal relationship between the mineralization and a late magmatic phase of the caldera cycle. A zone of extensive advanced argillically altered rocks trends from east to west through the caldera and is well delineated by Landsat Thematic Mapper data. Aeromagnetic and gravity data show that an east-west trending gravity and aeromagnetic high coincides with the distribution of the altered rock. The source of this geophysical anomaly is considered to be andesitic magma that intruded into the base of the volcanic pile and is regarded as the heat source responsible for hydrothermal circulation, niite and alunite K-Ar data indicate an age for the mineralization of 10.8 Ma. Recent drilling in the core of the system shows that hydrothermally altered rocks continue to depths of over 900 m and are characterized by assemblages typical of acid-sulfate epithermal systems. A deep sericitic zone, with chlorite present below about 500 m, grades upward into argillic, advanced argillic and silicic (vuggy silica) zones. Zonation of the alteration assemblages also occurs laterally; the advanced argillic alteration mineral assemblage is replaced by chlorite within the argillic zone at or near the ground surface.Ore deposits within the Rodalquilar complex consist of alunite, gold-alunite, and lead-zinc-silver-gold veins. The gold-alunite deposits are the most important economically. They are preferentially localized in ring and radial fractures of the Lomilla caldera nested within the Rodalquilar caldera. Gold extends over a vertical interval of about 200 m below the original paleosurface and changes at depth to a complex sulfide assemblage. Most gold was deposited in the highest part of the center of upwelling fluid following the peak of acidic alteration. Highest gold values, with a median near 8 g/t, occur in black, pyritic, banded chalcedony that fills preexisting open spaces and fractures within advanced argillically altered rocks. Hypogene alunite in the central core assemblage reaches depths of more than 300 m, is characterized by high sodium content, and is accompanied, below the zone of supergene oxidation, by kaolinite, zunyite, diaspore, pyrite and aluminum phosphate-sulfates. Stable isotope data indicate that this alunite formed in a magmatichydrothermal environment from the disproportionate of SO2 derived from a magma. The 6^4S data of coeval pyrite indicate the 834S of bulk sulfur in the system was ~7 per mil. Barren alunite-jarosite veins are extensive throughout the district to a depth of about 50 m. Stable isotope data from these alunites indicate that they were derived by the oxidation of H2S in a steam-heated environment that in some places was superimposed on the advanced argillic assemblage as the hydrotherma...

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Hydrothermal response to a volcano‐tectonic earthquake swarm, Lassen, California

Ingebritsen

Shelly

Hsieh

et al. 2015

Geophysical Research Letters

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The increasing capability of seismic, geodetic, and hydrothermal observation networks allows recognition of volcanic unrest that could previously have gone undetected, creating an imperative to diagnose and interpret unrest episodes. A November 2014 earthquake swarm near Lassen Volcanic National Park, California, which included the largest earthquake in the area in more than 60 years, was accompanied by a rarely observed outburst of hydrothermal fluids. Although the earthquake swarm likely reflects upward migration of endogenous H2O‐CO2 fluids in the source region, there is no evidence that such fluids emerged at the surface. Instead, shaking from the modest sized (moment magnitude 3.85) but proximal earthquake caused near‐vent permeability increases that triggered increased outflow of hydrothermal fluids already present and equilibrated in a local hydrothermal aquifer. Long‐term, multiparametric monitoring at Lassen and other well‐instrumented volcanoes enhances interpretation of unrest and can provide a basis for detailed physical modeling.

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The Lassen geothermal system

Abstract: This report will be published i n the proceedings of the Pacific Geothermal Conference , Auckl and, New Zeal and, November 1 982. ' 'PORTIONS OF THIS REPORT ARE ILLEEilBhE. B% has been reproduc:ed from the best available copy to permit the broadest ., rl possible availability.

Cited by 17 publications

References 0 publications

The Lassen hydrothermal system

The Lassen hydrothermal system

Preliminary study of the ore deposits and hydrothermal alteration in the Rodalquilar caldera complex, southeastern Spain

Hydrothermal response to a volcano‐tectonic earthquake swarm, Lassen, California

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