Helium isotope and gas discharge variations associated with crustal unrest in Long Valley Caldera, California, 1989–1992

Sorey, M.L.; Kennedy, B. Mack; Evans, William C.; Farrar, Christopher D.; Suemnicht, Gene A.

doi:10.1029/93jb00703

Cited by 82 publications

(40 citation statements)

References 41 publications

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“…Gas geothermometry, which at this time indicated temperatures near 150øC [Sorey et al, 1993a], is the basis for the value shown in Figure 10, although disequilibrium generation of H 2 at freshly cracked rock surfaces may cause errors in the geothermometry. The increased gas flow from the reservoir apparently reached the flank areas soon after reaching MMF.…”

Section: Gasmentioning

confidence: 74%

“…Mammoth Mountain also forms the southern end of the Inyo Craters volcanic chain that has produced intermittent rhyolitic and phreatic eruptions over the last 40,000 years, most recently about 600 years ago [Bailey, 1989;Miller, 1985]. The present-day period of unrest in the Long Valley In spite of its modest energy release, the 1989 Mammoth Mountain swarm is noteworthy because of its duration and evidence that it was accompanied by dike emplacement in the upper crust beneath the mountain [Hill, 1996;Hill et al, 1990;Sorey et al, 1993a]. The 1989 swarm also coincided with the onset of a continuing sequence of long-period (LP) volcanic earthquakes beneath and adjacent to the southwest flank of Mammoth Mountain [Pitt and Hill, 1994].…”

Section: Introductionmentioning

confidence: 99%

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Carbon dioxide and helium emissions from a reservoir of magmatic gas beneath Mammoth Mountain, California

Sorey¹,

Evans²,

Kennedy³

et al. 1998

J. Geophys. Res.

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Abstract. Carbon dioxide and helium with isotopic compositions indicative of a magmatic source (b 13C = -4.5 to -5%o, 3He/4He = 4.5 to 6.7 R^) are discharging at anomalous rates from Mammoth Mountain, on the southwestern rim of the Long Valley caldera in eastern California. The gas is released mainly as diffuse emissions from normal-temperature soils, but some gas issues from steam vents or leaves the mountain dissolved in cold groundwater. The rate of gas discharge increased significantly in 1989 following a 6-month period of persistent earthquake swarms and associated strain and ground deformation that has been attributed to dike emplacement beneath the mountain. An increase in the magmatic component of helium discharging in a steam vent on the north side of Mammoth Mountain, which also began in 1989, has persisted until the present time. Anomalous CO 2 discharge from soils first occurred during the winter of 1990 and was followed by observations of several areas of tree kill and/or heavier than normal needlecast the following summer. Subsequent measurements have confirmed that the tree kills are associated with CO 2 concentrations of 30-90% in soil gas and gas flow rates of up to 31,000 g m '2 d 4 at the soil surface. Each of the tree-kill areas and one area of CO 2 discharge above tree line occurs in close proximity to one or more normal faults, which may provide conduits for gas flow from depth. We estimate that the total diffuse CO 2 flux from the mountain is approximately 520 t/d, and that 30-50 t/d of CO 2 are dissolved in cold groundwater flowing off the flanks of the mountain. Isotopic and chemical analyses of soil and fumarolic gas demonstrate a remarkable homogeneity in composition, suggesting that the CO 2 and associated helium and excess nitrogen may be derived from a common gas reservoir whose source is associated with some combination of magmatic degassing and thermal metamorphism of metasedimentary rocks. Furthermore, N2/Ar ratios and nitrogen isotopic values indicate that the Mammoth Mountain gases are derived from sources separate from those that supply gas to the hydrothermal system within the Long Valley caldera. Various data suggest that the Mammoth Mountain gas reservoir is a large, lowtemperature cap over an isolated hydrothermal system, that it predates the 1989 intrusion, and that it could remain a source of gas discharge for some time.

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Section: Gasmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Carbon dioxide and helium emissions from a reservoir of magmatic gas beneath Mammoth Mountain, California

Sorey¹,

Evans²,

Kennedy³

et al. 1998

J. Geophys. Res.

Self Cite

200

178

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“…δ 13 C values of MMF CO 2 increased from -5.3‰ in July 1989 to -4.5‰ in August 1991, probably due to an increase in the magmatic CO 2 component in fumarolic gases [Sorey et al, 1993]. Overall, carbon and helium isotopic values likely indicate contribution of CO 2 from magmatic degassing and degassing of metasedimentary rocks.…”

Section: Lessons Learnedmentioning

confidence: 93%

“…In September 1989, distinct steam vents were observed and steam velocities from the ground had increased significantly. An increase in 3 He/ 4 He ratios measured in gases collected from MMF was observed following the onset of the 1989 earthquake swarm beneath Mammoth Mountain [Sorey et al, 1993]. For example, the 3 He/ He value increased by 58% (i.e., to 5.45 R A , where R A is the atmospheric 3 He/ 4 He ratio) from August to September 1989, and then continued to increase to a maximum value of 6.72 in July 1990 (Figure 2.4).…”

Section: Lessons Learnedmentioning

confidence: 96%

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Natural and industrial analogues for release of CO2 from storagereservoirs: Identification of features, events, and processes and lessonslearned

Lewicki¹,

Birkhölzer²,

Tsang³

2006

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. We thank J. Apps and A. Cortis for constructive review of this report. 2 EXECUTIVE SUMMARYThe injection and storage of anthropogenic CO 2 in deep geologic formations is a potentially feasible strategy to reduce CO 2 emissions and atmospheric concentrations. While the purpose of geologic carbon storage is to trap CO 2 underground, CO 2 could migrate away from the storage site into the shallow subsurface and atmosphere if permeable pathways such as well bores or faults are present. Large-magnitude releases of CO 2 have occurred naturally from geologic reservoirs in numerous volcanic, geothermal, and sedimentary basin settings. Carbon dioxide and natural gas have also been released from geologic CO 2 reservoirs and natural gas storage facilities, respectively, due to influences such as well defects and injection/withdrawal processes. These systems serve as natural and industrial analogues for the potential release of CO 2 from geologic storage reservoirs and provide important information about the key features, events, and processes (FEPs) that are associated with releases, as well as the health, safety, and environmental consequences of releases and mitigation efforts that can be applied.We describe a range of natural releases of CO 2 and industrial releases of CO 2 and natural gas in the context of these characteristics. Based on this analysis, several key conclusions can be drawn, and lessons can be learned for geologic carbon storage. First, CO 2 can both accumulate beneath, and be released from, primary and secondary reservoirs with capping units located at a wide range of depths. Both primary and secondary reservoir entrapments for CO 2 should therefore be well characterized at storage sites. Second, many natural releases of CO 2 have been correlated with a specific event that triggered the release, such as magmatic fluid intrusion or seismic activity. The potential for processes that could cause geomechanical damage to sealing cap rocks and trigger the release of CO 2 from a storage reservoir should be evaluated. Third, unsealed fault and fracture zones may act as fast and direct conduits for CO 2 flow from depth to the surface. Risk assessment should therefore emphasize determining the potential for and nature of CO 2 migration along these structures. Fourth, wells that are structurally unsound have the potential to rapidly release large quantities of CO 2 to the atmosphere. Risk assessment should therefore be focused on the potential for both active and abandoned wells at storage sites to transport CO 2 to the surface, particularly at sites with depleted oil or gas reservoirs where wells are abundant. Fifth, the style of CO 2 release at the surface varies widely between and within different leakage sites. In rare circumstances, the release of CO 2 can be a self-enhancing and/or eruptive process; this possibility should be assessed in the case of CO 2 leakage from storage reservoirs. Sixth, the hazard to human health has been small in most cases of large surface releases of CO 2 . This could be due to imp...

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From quiescence to unrest: 20 years of satellite geodetic measurements at Santorini volcano, Greece

et al. 2015

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Periods of unrest at caldera-forming volcanic systems characterized by increased rates of seismicity and deformation are well documented. Some can be linked to eventual eruptive activity, while others are followed by a return to quiescence. Here we use a 20 year record of interferometric synthetic aperture radar (InSAR) and GPS measurements from Santorini volcano to further our understanding of geodetic signals at a caldera-forming volcano during the periods of both quiescence and unrest, with measurements spanning a phase of quiescence and slow subsidence (1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010), followed by a phase of unrest (January 2011 to April 2012) with caldera-wide inflation and seismicity. Mean InSAR velocity maps from 1993-2010 indicate an average subsidence rate of~6 mm/yr over the southern half of the intracaldera island Nea Kameni. This subsidence can be accounted for by a combination of thermal contraction of the 1866-1870 lava flows and load-induced relaxation of the substrate. For the period of unrest, we use a joint inversion technique to convert InSAR measurements from three separate satellite tracks and GPS observations from 10 continuous sites into a time series of subsurface volume change. The optimal location of the inflating source is consistent with previous studies, situated north of Nea Kameni at a depth of~4 km. However, the time series reveals two distinct pressure pulses. The first pulse corresponds to a volume change (ΔV) within the shallow magma chamber of (11.56 ± 0.14) × 10 6 m 3 , and the second pulse has a ΔV of (9.73 ± 0.10) × 10 6 m 3 . The relationship between the timing of these pulses and microseismicity observations suggests that these pulses may be driven by two separate batches of magma supplied to a shallow reservoir. We find no evidence suggesting a change in source location between the two pulses. The decline in the rates of volume change at the end of both pulses and the observed lag of the deformation signal behind cumulative seismicity, suggest a viscoelastic response. We use a simple model to show that two separate pulses of magma intruding into a shallow magma chamber surrounded by a viscoelastic shell can account for the observed temporal variation in cumulative volume change and seismicity throughout the period of unrest. Given the similarities between the geodetic signals observed here and at other systems, this viscoelastic model has potential use for understanding behavior at other caldera systems.

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Helium isotope and gas discharge variations associated with crustal unrest in Long Valley Caldera, California, 1989–1992

Cited by 82 publications

References 41 publications

Carbon dioxide and helium emissions from a reservoir of magmatic gas beneath Mammoth Mountain, California

Carbon dioxide and helium emissions from a reservoir of magmatic gas beneath Mammoth Mountain, California

Natural and industrial analogues for release of CO2 from storagereservoirs: Identification of features, events, and processes and lessonslearned

From quiescence to unrest: 20 years of satellite geodetic measurements at Santorini volcano, Greece

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