More Like this

1. Iron Oxide (U–Th)/He Thermochronology: New Perspectives on Faults, Fluids, and Heat

   https://doi.org/10.2138/gselements.16.5.319  

   Cooperdock, Emily H.; Ault, Alexis K. (October 2020, Elements)

   null (Ed.)

   Fault zones record the dynamic motion of Earth’s crust and are sites of heat exchange, fluid–rock interaction, and mineralization. Episodic or long-lived fluid flow, frictional heating, and/or deformation can induce open-system chemical behavior and make dating fault zone processes challenging. Iron oxides are common in a variety of geologic settings, including faults and fractures, and can grow at surface-to magmatic temperatures. Recently, iron oxide (U–Th)/He thermochronology, coupled with microtextural and trace element analyses, has enabled new avenues of research into the timing and nature of fluid–rock interactions and deformation. These constraints are important for understanding fault zone evolution in space and time. 

   more » « less
2. Constraining Solid Dynamics, Interface Rheology, and Slab Hydration in the Hikurangi Subduction Zone Using 3‐Dimensional Fully Dynamic Models

   https://doi.org/10.1029/2024GC011824  

   Douglas, D; Naliboff, J; Fraters, M_R T; Dannberg, J; Eberhart‐Phillips, D; Ellis, S (June 2025, Geochemistry, Geophysics, Geosystems)

   Abstract Simulating present‐day solid Earth deformation and volatile cycling requires integrating diverse geophysical data sets and advanced numerical techniques to model complex multiphysics processes at high resolutions. Subduction zone modeling is particularly challenging due to the large geographic extent, localized deformation zones, and the strong feedbacks between reactive fluid transport and solid deformation. Here, we develop new workflows for simulating 3‐dimensional thermal‐mechanical subduction and patterns of volatile dehydration at convergent margins, adaptable to include reactive fluid transport. We apply these workflows to the Hikurangi margin, where recent geophysical investigations have offered unprecedented insight into the structure and processes coupling fluid transport and solid deformation across broad spatiotemporal scales. Geophysical data sets constraining the downgoing and overriding plate structure are collated with the Geodynamic World Builder, which provides the initial conditions for forward simulations using the open‐source geodynamic modeling software code ASPECT. We systematically examine how plate interface rheology and hydration of the downgoing plate and upper mantle influence Pacific–Australian convergence and seismic anisotropy. Models prescribing a plate boundary viscosity of Pa s best reproduce observed plate velocities, and changing the configuration of the Pacific–Australia plate boundary directly influences the modeled plate motions. Models considering hydrated olivine fabrics best reproduce observations of seismic anisotropy. Predicted patterns of slab dehydration and mantle melting correlate well with observations of seismic attenuation and arc volcanism. These results suggest that hydration‐related rheological heterogeneity and related fluid weakening may strongly influence slab dynamics. Future investigations integrating coupled fluid transport and global mantle flow will provide insight into the feedbacks between subduction dynamics, fluid pathways, and arc volcanism. 

   more » « less
3. How is continental crust built? A study of how fault zone deformation controls vertical transport of magma during crustal growth in Fiordland, New Zealand

   Brown, V.; Miranda, E.A. (April 2021, CSUNPosium: Annual Student Research and Creative Works Symposium)

   null (Ed.)

   Subduction zones are sites where converging tectonic plates create magma that is transported upward by faults (acting as conduits) within the crust, incrementally building the continent over time. However, how faults and their deep, ductile counterparts (shear zones) transport magma across the entire thickness of the crust is not well understood. This is important to investigate because faults remain as zones of weakness and may trigger large magnitude earthquakes (Barnes et al., 2016). Fiordland, New Zealand, has a system of interconnected faults and shear zones that transect the world’s best-preserved section of crust produced in a subduction zone. We will focus on shear zone rocks from the middle crust, where the shear zone narrows in width as the composition of the crust changes. We hypothesize that the change in crustal composition acted as a strength boundary within the shear zone, changing the geometry of strain to allow for more localized movement of magma and deformation. 

   more » « less
4. Subduction Zone Obliquity Dictates Global Trench‐Parallel Inner Forearc Deformation

   https://doi.org/10.1029/2024AV001468  

   Morell, Kristin_D; Gilroy, Kellan; Finley, Theron; Harrichhausen, Nicolas (February 2025, AGU Advances)

   Abstract Although subduction zones are characterized by convergence, the upper plates of subduction zones exhibit a diverse range of deformation styles that are often inconsistent with regional convergence. While several theories have been proposed to explain these variations, the underlying factors driving these differences are still not fully understood. In this study, we analyze 24,000 km of active global subduction zones around the globe to determine how subduction zone obliquity affects deformation in the trench‐parallel and horizontal directions on land above subduction zones. We take advantage of recently published worldwide data sets of Global Navigation Satellite System (GNSS) velocities and global active fault catalogs in order to examine deformation at 13 of the world's forearcs. We analyze deformation over both short (decadal) timescales, captured by GNSS, and long (millennial to million‐year) timescales, observed through trench‐parallel active forearc faults. The results reveal a strong link between subduction obliquity and both the sense and amount of forearc rotation detected by GNSS, as well as the sense and rate of deformation along trench‐parallel strike‐slip faults. Unlike previous studies indicating that subduction obliquity affects forearc deformation only beyond a certain threshold, we demonstrate that even low to moderate obliquity significantly influences the observed deformation. 

   more » « less
5. Carbonation and decarbonation reactions: Implications for planetary habitability

   https://doi.org/10.2138/am-2019-6884  

   Stewart, E.M.; Ague, Jay J.; Ferry, John M.; Schiffries, Craig M.; Tao, Ren-Biao; Isson, Terry T.; Planavsky, Noah J. (October 2019, American Mineralogist)

   Abstract The geologic carbon cycle plays a fundamental role in controlling Earth's climate and habitability. For billions of years, stabilizing feedbacks inherent in the cycle have maintained a surface environment that could sustain life. Carbonation/decarbonation reactions are the primary mechanisms for transferring carbon between the solid Earth and the ocean–atmosphere system. These processes can be broadly represented by the reaction: CaSiO3 (wollastonite) + CO2 (gas) ↔ CaCO3 (calcite) + SiO2 (quartz). This class of reactions is therefore critical to Earth's past and future habitability. Here, we summarize their significance as part of the Deep Carbon Obsevatory's “Earth in Five Reactions” project. In the forward direction, carbonation reactions like the one above describe silicate weathering and carbonate formation on Earth's surface. Recent work aims to resolve the balance between silicate weathering in terrestrial and marine settings both in the modern Earth system and through Earth's history. Rocks may also undergo carbonation reactions at high temperatures in the ultramafic mantle wedge of a subduction zone or during retrograde regional metamorphism. In the reverse direction, the reaction above represents various prograde metamorphic decarbonation processes that can occur in continental collisions, rift zones, subduction zones, and in aureoles around magmatic systems. We summarize the fluxes and uncertainties of major carbonation/decarbonation reactions and review the key feedback mechanisms that are likely to have stabilized atmospheric CO2 levels. Future work on planetary habitability and Earth's past and future climate will rely on an enhanced understanding of the long-term carbon cycle. 

   more » « less