More Like this

1. An introductory review of the thermal structure of subduction zones: I—motivation and selected examples

   https://doi.org/10.1186/s40645-023-00573-z  

   van_Keken, Peter E; Wilson, Cian R (December 2023, Progress in Earth and Planetary Science)

   Tada, R (Ed.)

   The thermal structure of subduction zones is fundamental to our understanding of physical and chemical processes that occur at active convergent plate margins. These include magma generation and related arc volcanism, shallow and deep seismicity, and metamorphic reactions that can release fluids. Computational models can predict the thermal structure to great numerical precision when models are fully described but this does not guarantee accuracy or applicability. In a trio of companion papers, the construction of thermal subduction zone models, their use in subduction zone studies, and their link to geophysical and geochemical observations are explored. In part I, the motivation to understand the thermal structure is presented based on experimental and observational studies. This is followed by a description of a selection of thermal models for the Japanese subduction zones. 

   more » « less
2. An introductory review of the thermal structure of subduction zones: III—Comparison between models and observations

   https://doi.org/10.1186/s40645-023-00589-5  

   van Keken, Peter E.; Wilson, Cian R. (September 2023, Progress in Earth and Planetary Science)

   Abstract The thermal structure of subduction zones is fundamental to our understanding of the physical and chemical processes that occur at active convergent plate margins. These include magma generation and related arc volcanism, shallow and deep seismicity, and metamorphic reactions that can release fluids. Computational models can predict the thermal structure to great numerical precision when models are fully described but this does not guarantee accuracy or applicability. In a trio of companion papers, the construction of thermal subduction zone models, their use in subduction zone studies, and their link to geophysical and geochemical observations are explored. In this last part, we discuss how independent finite element approaches predict the thermal structure of the global subduction system and investigate how well these predictions correspond to geophysical, geochemical, and petrological observations. 

   more » « less
3. An introductory review of the thermal structure of subduction zones: II—numerical approach and validation

   https://doi.org/10.1186/s40645-023-00588-6  

   Wilson, Cian R.; van Keken, Peter E. (November 2023, Progress in Earth and Planetary Science)

   Abstract The thermal structure of subduction zones is fundamental to our understanding of the physical and chemical processes that occur at active convergent plate margins. These include magma generation and related arc volcanism, shallow and deep seismicity, and metamorphic reactions that can release fluids. Computational models can predict the thermal structure to great numerical precision when models are fully described but this does not guarantee accuracy or applicability. In a trio of companion papers, the construction of thermal subduction zone models, their use in subduction zone studies, and their link to geophysical and geochemical observations are explored. In this part II, the finite element techniques that can be used to predict thermal structure are discussed in an introductory fashion along with their verification and validation. Steady-state thermal structure for the updated subduction zone benchmark. a) Temperature predicted by TF for case 1; b) temperature difference between TF and Sepran using the penalty function (PF) method for case 1 at f_m=1 where f_mrepresents the smallest element sizes in the finite element grids near the coupling point; c) slab top temperature comparison for case 1; and d)–f) as a)–c) but now for case 2. The star indicates the position or temperature conditions at the coupling point. 

   more » « less
4. Tracing Fluid‐Rock Interactions and Migration Pathways in Shallow Megathrust Shear Zones Through Rock Magnetic Analysis

   https://doi.org/10.1029/2025JB031374  

   Robustelli_Test, Claudio; Bilardello, Dario; Zanella, Elena; Ghignone, Stefano; Pellegrino, Luca; Ferrara, Enzo; Festa, Andrea; Remitti, Francesca (September 2025, Journal of Geophysical Research: Solid Earth)

   Abstract Megathrust shear zones are the main fluid transport pathways during the seismic cycle and play a key role in controlling physicochemical alteration. Defining fluid‐rock interaction in wall rocks provides evidence for unraveling the hydrogeology of shear zones and their link to active fluid circulation. We analyzed the variation in concentration, grain size and assemblages of magnetic minerals in the wall rocks of a shallow megathrust (the Sestola Vidiciatico shear zone) where no evidence of high‐frictional heating has been recorded. The Sestola Vidiciatico shear zone preserves evidence of active fluid circulation and stress‐switch during the last brittle phases of the Early to Middle Miocene subduction of the Adriatic plate beneath the frontal prism of the European plate. Magnetic properties indicate low bulk heat transfer during the seismic cycle. Changes in magnetic mineral concentrations highlight iron depletion from clay minerals and dissolution of iron‐oxides for interaction with exotic fluids during the coseismic phase. The relative distribution of Fe‐oxides and goethite suggests migration of Fe‐enriched fluids along fractures during the coseismic/postseismic phase, followed by precipitation for interaction with local fluids. Subsequent alteration and weathering of magnetic minerals, accompanied by the formation of hematite and maghemite, are related to partial oxidation during the interseismic phase. Heterogeneity in magnetic mineral distribution supports active fluid circulation during repeated seismic events and/or exhumation. Rock magnetic characterization of wall rocks in exhumed megathrust represents a promising tool to better understand the role of fluid migration and redox conditions during seismic cycles in subduction zones. 

   more » « less
5. Deep decoupling in subduction zones: Observations and temperature limits

   https://doi.org/10.1130/GES02278.1  

   Abers, Geoffrey A.; van Keken, Peter E.; Wilson, Cian R. (October 2020, Geosphere)

   null (Ed.)

   Abstract The plate interface undergoes two transitions between seismogenic depths and subarc depths. A brittle-ductile transition at 20–50 km depth is followed by a transition to full viscous coupling to the overlying mantle wedge at ∼80 km depth. We review evidence for both transitions, focusing on heat-flow and seismic-attenuation constraints on the deeper transition. The intervening ductile shear zone likely weakens considerably as temperature increases, such that its rheology exerts a stronger control on subduction-zone thermal structure than does frictional shear heating. We evaluate its role through analytic approximations and two-dimensional finite-element models for both idealized subduction geometries and those resembling real subduction zones. We show that a temperature-buffering process exists in the shear zone that results in temperatures being tightly controlled by the rheological strength of that shear zone’s material for a wide range of shear-heating behaviors of the shallower brittle region. Higher temperatures result in weaker shear zones and hence less heat generation, so temperatures stop increasing and shear zones stop weakening. The net result for many rheologies are temperatures limited to ≤350–420 °C along the plate interface below the cold forearc of most subduction zones until the hot coupled mantle is approached. Very young incoming plates are the exception. This rheological buffering desensitizes subduction-zone thermal structure to many parameters and may help explain the global constancy of the 80 km coupling limit. We recalculate water fluxes to the forearc wedge and deep mantle and find that shear heating has little effect on global water circulation. 

   more » « less