An official website of the United States government
Abstract Transition to cleaner energy sources is crucial for reducing carbon emissions to zero. Among these new clean energy types, there is a growing awareness of the potential for naturally occurring geologic hydrogen (H2) as a primary energy resource that can be readily introduced into the existing energy supply. It is anticipated that geophysics will play a critical role in such endeavors. There are two major different types of geologic H2. One is natural H2 (referred to as gold H2), which is primarily accumulating naturally in reservoirs in certain geological setting; and the other is stimulated H2 (referred to as orange H2), which is produced artificially from source rocks through chemical and physical stimulations. We will first introduce geophysics in geologic H2 in comparison and contrast to the scenarios of blue and green H2. We will then discuss the significance of geophysics in both natural H2 and stimulated H2 in term of both exploration and monitoring tools. Comparing and contrasting the current geophysical tools in hydrocarbon exploration and production, we envision the innovative geophysical technologies and strategies for geologic H2 resources based on our current understanding of both natural and stimulated geologic hydrogen systems. The strategies for H2 exploration will involve a shift from reservoir- to source rock-centered approaches. Last, we believe that the geophysical methods including integration of multi-geophysics, efficient data acquisition, and machine learning in geologic H2 could be potentially provide sufficient new directions and significant opportunities to pursue research for the next one or two decades.
more »
« less
This content will become publicly available on August 4, 2026
Where could geologic hydrogen generation happen in UAE? Mapping serpentinization in the ophiolite blocks using MT phase tensors
Abstract Geologic hydrogen has emerged as a primary energy source, drawing growing interest from the scientific community and the energy sector. One of the primary geochemical mechanisms for natural hydrogen generation is serpentinization, which is the hydration of mafic and ultramafic rocks. The United Arab Emirates (UAE) is home to one of the largest ophiolite blocks in the world, making it a promising area for geologic hydrogen exploration. In this study, we apply magnetotelluric (MT) phase tensor analysis to detect electrical anisotropy associated with serpentinization in the mantle peridotite sequence. The alignment of olivine crystals and hydrous minerals such as serpentine impart electrical anisotropy to these rocks. Current approaches for detecting serpentinization have primarily focused on changes in bulk physical properties, often overlooking the directional dependencies and complexities introduced by anisotropy. In this research, we introduce a novel geophysical framework based on the phase tensors, to identify serpentinized zones within source rocks in geologic hydrogen systems and possibly identify potential hydrogen-bearing zones. Using MT field data from the UAE, we demonstrate that phase tensor analysis effectively identifies anisotropic conductivity zones associated with serpentinization. The MT phase tensor approach we propose can support assessment of geologic hydrogen generation and its lifecycle.
more »
« less
- PAR ID:
- 10641872
- Publisher / Repository:
- Research Square
- Date Published:
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
The conditions of methane (CH 4 ) formation in olivine-hosted secondary fluid inclusions and their prevalence in peridotite and gabbroic rocks from a wide range of geological settings were assessed using confocal Raman spectroscopy, optical and scanning electron microscopy, electron microprobe analysis, and thermodynamic modeling. Detailed examination of 160 samples from ultraslow- to fast-spreading midocean ridges, subduction zones, and ophiolites revealed that hydrogen (H 2 ) and CH 4 formation linked to serpentinization within olivine-hosted secondary fluid inclusions is a widespread process. Fluid inclusion contents are dominated by serpentine, brucite, and magnetite, as well as CH 4( g ) and H 2( g ) in varying proportions, consistent with serpentinization under strongly reducing, closed-system conditions. Thermodynamic constraints indicate that aqueous fluids entering the upper mantle or lower oceanic crust are trapped in olivine as secondary fluid inclusions at temperatures higher than ∼400 °C. When temperatures decrease below ∼340 °C, serpentinization of olivine lining the walls of the fluid inclusions leads to a near-quantitative consumption of trapped liquid H 2 O. The generation of molecular H 2 through precipitation of Fe(III)-rich daughter minerals results in conditions that are conducive to the reduction of inorganic carbon and the formation of CH 4 . Once formed, CH 4( g ) and H 2( g ) can be stored over geological timescales until extracted by dissolution or fracturing of the olivine host. Fluid inclusions represent a widespread and significant source of abiotic CH 4 and H 2 in submarine and subaerial vent systems on Earth, and possibly elsewhere in the solar system.more » « less
-
Abstract Antigorite is a hydrous sheet silicate with strongly anisotropic seismic and rheological properties. Hydrous minerals such as antigorite have been invoked to explain numerous geologic observations within subduction zones including intermediate‐depth earthquakes, arc volcanism, the persistent weakness of the subduction interface, trench‐parallelSwave splitting, and episodic tremor and slip. To understand how the presence of antigorite‐bearing rocks affects observations of seismic anisotropy, three mylonites from the Kohistan palaeo‐island arc in Pakistan were analysed using electron backscatter diffraction. A fourth sample, which displayed optical evidence for crystallographically controlled replacements of olivine, was also investigated using electron backscatter diffraction to identify potential topotactic relationships. The resulting data were used to model the bulk seismic properties of antigorite‐rich rocks. The mylonitic samples exhibit incredibly strong bulk anisotropy (10–20% for the antigorite + olivine). Within the nominally undeformed protomylonite, two topotactic relationships were observed: (1) (010)ant//(100)ol with [100]ant//[001]ol and (2) (010)ant//(100)ol with [100]ant//[010]ol. However, the strength of a texture formed by topotactic replacement is markedly weaker than the strength of the textures observed in mylonitic samples. Since antigorite is thought to be rheologically weak, we hypothesise that microstructures formed from topotactic reactions will be progressively overprinted as deformation is localised in regions with greater percentages of serpentine. Regions of highly sheared serpentine, therefore, have the potential to strongly influence seismic wave speeds in subduction settings. The presence of deformed antigorite in a dipping structure is one explanation for observations of both the magnitude and splitting pattern of seismic waves in subduction zones.more » « less
-
Abstract Devastating seismic events occur mainly in subduction zones, and a significant percentage of them are intraslab earthquakes. The geologic record of these events holds valuable information that needs to be investigated for a comprehensive seismic risk assessment. Here we investigate pseudotachylytes formed in oceanic peridotites and that are interpreted to result from intraslab seismic rupture. Each vein has recorded the seismic slip direction and slip sense of a single coseismic shear‐heating event. The well‐preserved exposures, showing individual veins up to 7 m in length and about 3 cm in width, of Cima di Gratera, in the Schistes Lustrés ophiolitic units of Corsica, offer unparalleled opportunities to investigate intraslab rupture kinematics in mantle rocks. The principal ferromagnetic phase in these rocks is a Ti‐poor magnetite. We use the anisotropy of magnetic susceptibility (AMS) recorded in pseudotachylyte generation veins (bulk susceptibilities range from 600 to 20,000 × 10−6[SI] volume, withP′ ranging from 1.05 to 2.5) to reconstruct the co‐seismic deformation parameters, that is, fault plane attitude, direction and sense of slip. These new results, internally consistent at the vein level, span across oblate and prolate symmetries and reveal that seismic deformation recorded in these veins was kinematically diverse and included mostly normal mechanisms acting along the same subduction zone. In addition, our investigations show that the magnetic fabric of peridotite‐hosted pseudotachylytes provides key information bearing on the complex dynamics of frictional melts at a unprecedently high spatial resolution.more » « less
-
Abstract Volcanic arcs consist of many distinct vents that are ultimately fueled by the common melting processes in the subduction zone mantle wedge. Seismic imaging of crustal‐scale magmatic systems can provide insight into how melt is organized in the deep crust and eventually focused beneath distinct vents as it ascends and evolves. Here, we investigate the crustal‐scale structure beneath a section of the Cascades arc spanning four major stratovolcanoes: Mt. Hood, Mt. St. Helens (MSH), Mt. Adams (MA), and Mt. Rainier, based on ambient noise data from 234 seismographs. Simultaneous inversion of Rayleigh and Love wave dispersion constrains the isotropic shear velocity (Vs) and identifies radially anisotropic structures. IsotropicVsshows two sub‐parallel low‐Vszones (∼3.45–3.55 km/s) at ∼15–30 km depth with one connecting Mt. Rainier to MA, and another connecting MSH to Mt. Hood, which are interpreted as deep crustal magma reservoirs containing up to ∼2.5%–6% melt, assuming near‐equilibrium melt geometry. Negative radial anisotropy, from vertical fractures like dikes, is prevalent in this part of the Cascadia, but is interrupted by positive radial anisotropy, from subhorizontal features like sills, extending vertically beneath MA and Mt. Rainier at ∼10–30 km depth and weaker and west‐dipping positive anisotropy beneath MSH. The positive anisotropy regions are adjacent to rather than co‐located with the isotropic low‐Vsanomalies. Ascending melt that stalled and mostly crystallized in sills with possible compositional differences from the country rock may explain the near‐averageVsand positive radial anisotropy adjacent to the active deep crustal magma reservoirs.more » « less
