Geologically consistent multiphysics imaging of the Darajat geothermal steam field

Soyer, Wolfgang; Mackie, Randall L.; Hallinan, S.; Pavesi, A.; Nordquist, Gregg; Suminar, Aquardi; Intani, Rindu Grahabhakti; Nelson, Chris

doi:10.3997/1365-2397.n0102

Cited by 20 publications

(8 citation statements)

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“…Indeed, critical points of pure water and seawater range between 373°C at 220 bar and 403°C at 298 bar, respectively. On volcanoes and geothermal areas, the presence of steam, or supercritical water in porous media is known to increase electrical resistivity compared to a liquid water phase (e.g., Árnason et al., 2010; Gasperikova et al., 2015; Hersir et al., 2020; Piña‐Varas et al., 2014; Soyer et al., 2018; Yamaya et al., 2013). Such field observations are also attested by numerous laboratory measurements (e.g., Klumbach & Keppler, 2020; Nono et al., 2020; Quist & Marshall, 1968; Roberts et al., 2001).…”

Section: Discussionmentioning

confidence: 99%

Hydrothermal and Magmatic System of a Volcanic Island Inferred From Magnetotellurics, Seismicity, Self‐potential, and Thermal Image: An Example of Miyakejima (Japan)

et al. 2021

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Active hydrothermal systems develop during repose periods of volcanoes within the first kilometers of their edifices when ascending hot magmatic fluids (liquid or gas) encounter meteoric water recharge and/or seawater. Free convection and forced circulation occur, leading to surface manifestations such as fumaroles and hot springs.Intensive volcanic hazards are associated with pervasive hydrothermal systems. Phreatic and phreatomagmatic eruptions represent the most common hazards occurring when hot magmatic fluids or magma are injected into a pre-existing hydrothermal system (Heiken & Wohletz, 1987;Stix, 2018). Pore-water is flashed creating an overpressure until the potential rupture of host-rock, leading to a sudden explosive eruption (e.g., Mannen et al., 2019;Yamaoka et al., 2016). Other hydrothermal-related hazards exist without necessarily involving magmatic origin. Indeed, long-term host-rock interactions between heat, water, and magmatic fluids lead to numerous modifications of the physical-chemical properties of host rocks and fluids. Percolation of hot and acidic fluids (<400°C) dissolves host-rock primary minerals and precipitates low-permeability clay minerals (Pirajno, 2008). Such alteration products create a barrier to the flow of fluids (called Abstract Phreatic and phreatomagmatic eruptions represent some of the greatest hazards occurring on volcanoes. They result from complex interactions at a depth between rock, water, and magmatic fluids. Understanding and assessing such processes remain a challenging task, notably because a large-scale characterization of volcanic edifices is often lacking. Here we focused on Miyakejima Island, an inhabited 8-km-wide stratovolcano with regular phreatomagmatic activity. We imaged its plumbing system through a combination of four geophysical techniques: magnetotellurics, seismicity, self-potential, and thermal image. We thus propose the first comprehensive interpretation of the volcanic island in terms of rock properties, temperature, fluid content, and fluid flow. We identify a shallow aquifer lying above a clay cap (<1 km depth) and reveal its relation with magmatic-tectonic features and past eruptive activity. At greater depths (2-4.5 km), we infer a seismogenic resistive region interpreted as a magmatic gas-rich reservoir (≥370°C). From this reservoir, gases rise through a fractured conduit before being released in the fumarolic area at ∼180°C. During their ascent, these hot fluids cross a ∼1.2-km-long liquid-dominated zone causing local steam explosions. Such magmatic-hydrothermal interaction elucidates (i) the origin of the long-period seismic events and (ii) the mixing mechanism between magmatic and hydrothermal fluids, which was previously observed in the geochemical signature of fumaroles. Our results demonstrate that combining multidisciplinary large-scale methods is a relevant approach to better understand volcanic systems, with implications for monitoring strategies. GRESSE ET AL.

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Section: Discussionmentioning

confidence: 99%

Hydrothermal and Magmatic System of a Volcanic Island Inferred From Magnetotellurics, Seismicity, Self‐potential, and Thermal Image: An Example of Miyakejima (Japan)

et al. 2021

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“…While the relationship between low grain density and high conductivity has been seen in other experimental studies (e.g., Nelson and Anderson, 1992), this is perhaps underappreciated in the context of geophysical imaging in geothermal systems. These data suggest that joint inversions of gravimetric and electromagnetic measurements, particularly when combined with porosity constraints based on core measurements and geologic modeling (e.g., Soyer et al, 2018), may facilitate better delineation of the geometry of the cap rock, precise knowledge of which is essential to target the underlying higher-temperature resistive core.…”

Section: Relationships Between Grain Density and Electricalmentioning

confidence: 99%

Valgarður: a database of the petrophysical, mineralogical, and chemical properties of Icelandic rocks

Scott

Levy²,

Covell

et al. 2023

Earth Syst. Sci. Data

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Abstract. The Valgarður database is a compilation of data describing the physical and geochemical properties of Icelandic rocks. The dataset comprises 1166 samples obtained from fossil and active geothermal systems as well as from relatively fresh volcanic rocks erupted in subaerial or subaqueous environments. The database includes petrophysical properties (connected and total porosity, grain density, permeability, electrical resistivity, acoustic velocities, rock strength, and thermal conductivity) as well as mineralogical and geochemical data obtained by point counting, X-ray fluorescence (XRF), quantitative X-ray diffraction (XRD), and cation exchange capacity (CEC) analyses. The database may be accessed at https://doi.org/10.5281/zenodo.6980231 (Scott et al., 2022a). We present the database and use it to characterize the relationship between lithology, alteration, and petrophysical properties. The motivation behind this database is to (i) aid in the interpretation of geophysical data, including uncertainty estimations; (ii) facilitate the parameterization of numerical reservoir models; and (iii) improve the understanding of the relationship between rock type, hydrothermal alteration, and petrophysical properties.

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“…The MT modeling code used in this work is a proprietary commercial code that has a long history of use and has been benchmarked against semi‐analytical results and other numerical codes (e.g., Mackie & Watts, 2012; Miensopust et al., 2013). It has been used extensively for commercial exploration projects including oil and gas, geothermal, mining, and marine EM (e.g., Hoversten et al., 2021; Mackie et al., 2020; Soyer et al., 2018).…”

Section: Synthetic Modelmentioning

confidence: 99%

Magnetotelluric Investigations of the Kīlauea Volcano, Hawaii

Hoversten¹,

Newman²,

Gasperikova³

et al. 2022

JGR Solid Earth

Self Cite

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In 2002 and 2003 a collaborative effort was undertaken between Lawrence Berkeley National Laboratory, Sandia National Laboratories, the U.S. Geological Survey (USGS) Menlo Park, the USGS Hawaiian Volcano Observatory, and Electromagnetic Instruments Inc. to study the Kīlauea volcano in Hawaii using the magnetotelluric (MT) technique. The work was motivated by a desire to improve understanding of the magma reservoirs and conduits within Kīlauea and the East and Southwest Rift zones, which has implications for understanding Kīlauea's plumbing system. An improved understanding of the rift zones has implications in understanding large‐scale landslides that are generated in the Hilina Slump, which produce significant impacts on coastal communities. Up to eight stations operated simultaneously, with multiple remote reference sites, and data were processed using multi‐station robust processing techniques. In total, data were acquired at 70 sites over the Southwest and East rift zones. Good to excellent quality data were obtained even in the harshest conditions, such as those encountered on the fresh lava flows of the East Rift Zone, where electrical contact resistances are on the order of 100 kΩ. A three‐dimensional (3D) MT model study was done to guide interpretation of the observed MT measurements. Synthetic modeling demonstrates that conductive bodies in the upper 3 km can be spatially resolved where MT station sampling is good. Resistivity anomalies in the 3D inversions have a high degree of spatial correlation with previously published seismic velocity anomalies beneath Kīlauea. Melt fractions between 0.096 and 0.117 are calculated for the Kīlauea and Puʻuʻōʻō low resistivity anomalies, respectively.

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Geologically consistent multiphysics imaging of the Darajat geothermal steam field

Cited by 20 publications

References 0 publications

Hydrothermal and Magmatic System of a Volcanic Island Inferred From Magnetotellurics, Seismicity, Self‐potential, and Thermal Image: An Example of Miyakejima (Japan)

Hydrothermal and Magmatic System of a Volcanic Island Inferred From Magnetotellurics, Seismicity, Self‐potential, and Thermal Image: An Example of Miyakejima (Japan)

Valgarður: a database of the petrophysical, mineralogical, and chemical properties of Icelandic rocks

Magnetotelluric Investigations of the Kīlauea Volcano, Hawaii

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