The Role of Volatiles in Reactive Melt Transport in the Asthenosphere

Keller, Tobias; Katz, Richard F.

doi:10.1093/petrology/egw030

Cited by 130 publications

(100 citation statements)

References 82 publications

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“…Following previous studies (McKenzie, ; Katz, ; Keller and Katz, ; Scott and Stevenson, ), mass conservation for liquid and solid phases in porous media are expressed as

\frac{\partial ϕ}{\partial t} + \nabla \cdot false({bold-italicv}_{f} ϕ false) = \frac{normalΓ}{ρ_{f}},

\frac{\partial false(1 - ϕ false)}{\partial t} + \nabla \cdot false[{bold-italicv}_{s} false(1 - ϕ false) false] = - \frac{normalΓ}{ρ_{s}},

where densities of both phases are assumed to be constant, and the meaning of the symbols is listed in Table . In addition, the conservation of volatile species H 2 O and CO 2 in both phases are

\frac{\partial false(ρ_{f} ϕ c_{f}^{i} false)}{\partial t} + \nabla \cdot false(ρ_{f} {bold-italicv}_{f} ϕ c_{f}^{i} false) = {normalΓ}_{i},

\frac{\partial false[ρ_{s} false(1 - ϕ false) c_{s}^{i} false]}{\partial t} + \nabla \cdot false[ρ_{s} {bold-italicv}_{s} false(1 - ϕ false) c_{s}^{i} false] = - {normalΓ}_{i},

where i represents either H 2 O or CO 2 .…”

Section: Model Setupmentioning

confidence: 99%

Devolatilization of Subducting Slabs, Part II: Volatile Fluxes and Storage

Tian

Katz

Jones

et al. 2019

Geochem Geophys Geosyst

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Subduction is a crucial part of the long-term water and carbon cycling between Earth's exosphere and interior. However, there is broad disagreement over how much water and carbon is liberated from subducting slabs to the mantle wedge and transported to island-arc volcanoes. In the Tian et al. (2019) Part I, we parameterize the metamorphic reactions involving H 2 O and CO 2 for representative subducting lithologies. On this basis, a two-dimensional reactive transport model is constructed in this Part II. We assess the various controlling factors of CO 2 and H 2 O release from subducting slabs. Model results show that up-slab fluid flow directions produce a flux peak of CO 2 and H 2 O at subarc depths. Moreover, infiltration of H 2 O-rich fluids sourced from hydrated slab mantle enhances decarbonation or carbonation at lithological interfaces, increases slab surface fluxes, and redistributes CO 2 from basalt and gabbro layers to the overlying sedimentary layer. As a result, removal of the cap sediments (by diapirism or off-scraping) leads to elevated slab surface CO 2 and H 2 O fluxes. The modeled subduction efficiency (the percentage of initially subducted volatiles retained until ∼200 km deep) of H 2 O and CO 2 is increased by open-system effects due to fractionation within the interior of lithological layers.

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“…Following previous studies (McKenzie, ; Katz, ; Keller and Katz, ; Scott and Stevenson, ), mass conservation for liquid and solid phases in porous media are expressed as

\frac{\partial ϕ}{\partial t} + \nabla \cdot false({bold-italicv}_{f} ϕ false) = \frac{normalΓ}{ρ_{f}},

\frac{\partial false(1 - ϕ false)}{\partial t} + \nabla \cdot false[{bold-italicv}_{s} false(1 - ϕ false) false] = - \frac{normalΓ}{ρ_{s}},

where densities of both phases are assumed to be constant, and the meaning of the symbols is listed in Table . In addition, the conservation of volatile species H 2 O and CO 2 in both phases are

\frac{\partial false(ρ_{f} ϕ c_{f}^{i} false)}{\partial t} + \nabla \cdot false(ρ_{f} {bold-italicv}_{f} ϕ c_{f}^{i} false) = {normalΓ}_{i},

\frac{\partial false[ρ_{s} false(1 - ϕ false) c_{s}^{i} false]}{\partial t} + \nabla \cdot false[ρ_{s} {bold-italicv}_{s} false(1 - ϕ false) c_{s}^{i} false] = - {normalΓ}_{i},

where i represents either H 2 O or CO 2 .…”

Section: Model Setupmentioning

confidence: 99%

Devolatilization of Subducting Slabs, Part II: Volatile Fluxes and Storage

Tian

Katz

Jones

et al. 2019

Geochem Geophys Geosyst

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“…In this perspective, the development of 2‐D THCM models will benefit from the presented mechanical solvers (M). The latter will be used as the main building block to further tackle studies of thermomechanical shear localization [ Duretz et al ., ] (TM coupling), two‐phase flow [ Yarushina and Podladchikov , ] leading to fluid channeling instabilities [ Yarushina et al ., ; Räss et al ., ] (HM coupling), reactive porosity waves [ Malvoisin et al ., ] (HCM coupling), or THCM coupling [ Keller and Katz , ; Weatherley and Katz , ]. Features arising from THCM coupling are often localized in space, close to material interfaces (e.g., shear zones, fluid channeling) and may depend on the local pressure field.…”

Section: Discussionmentioning

confidence: 99%

M2Di: Concise and efficient MATLAB 2‐D Stokes solvers using the Finite Difference Method

Räss

Duretz

Podladchikov

et al. 2017

Geochem Geophys Geosyst

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Recent development of many multiphysics modeling tools reflects the currently growing interest for studying coupled processes in Earth Sciences. The core of such tools should rely on fast and robust mechanical solvers. Here we provide M2Di, a set of routines for 2-D linear and power law incompressible viscous flow based on Finite Difference discretizations. The 2-D codes are written in a concise vectorized MATLAB fashion and can achieve a time to solution of 22 s for linear viscous flow on 1000 2 grid points using a standard personal computer. We provide application examples spanning from finely resolved crystal-melt dynamics, deformation of heterogeneous power law viscous fluids to instantaneous models of mantle flow in cylindrical coordinates. The routines are validated against analytical solution for linear viscous flow with highly variable viscosity and compared against analytical and numerical solutions of power law viscous folding and necking. In the power law case, both Picard and Newton iterations schemes are implemented. For linear Stokes flow and Picard linearization, the discretization results in symmetric positive-definite matrix operators on Cartesian grids with either regular or variable grid spacing allowing for an optimized solving procedure. For Newton linearization, the matrix operator is no longer symmetric and an adequate solving procedure is provided. The reported performance of linear and power law Stokes flow is finally analyzed in terms of wall time. All MATLAB codes are provided and can readily be used for educational as well as research purposes. The M2Di routines are available from Bitbucket and the University of Lausanne Scientific Computing Group website, and are also supplementary material to this article.

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“…The viscous heating is also negligible because the solid rotational flow only produces a small heat, and the compaction deformation is comparable to the rotational deformation. The melting rate

\overset{Γ}{true}

is determined by the difference between the equilibrium melt fraction and the melt present in any infinitesimal parcel (Dannberg & Heister, ; Katz, & Weatherley, ; Keller & Katz, ).

\overset{Γ}{true} = italicRe ()(, ϕ^{eq} - ϕ)

where Re is the reaction rate (Table ; Keller & Katz, ), and the equilibrium melt fraction φ eq is scaled by the temperature difference between the liquidus ( T L ) and the solidus ( T S )

ϕ^{eq} = \frac{T - T_{S}}{T_{L} - T_{S}} with italicTS = T_{S italic0} ()(, p) + normalΔ T_{F} F

where T S0 (p) is the sediment solidus without depletion, F is the degree of melting (depletion), and Δ T F represents the effect of depletion on the solidus (Figure ).…”

Section: Model Description and Methodsmentioning

confidence: 99%

Melt Segregation and Depletion During Ascent of Buoyant Diapirs in Subduction Zones

et al. 2020

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Cold, low‐density diapirs arising from hydrated mantle and/or subducted sediments on the top of subducting slabs have been invoked to transport key chemical signatures to the source region of arc magmas. However, to date there have been few quantitative models to constrain melting in such diapirs. Here we use a two‐phase Darcy‐Stokes‐energy model to investigate thermal evolution, melting, and depletion in a buoyant sediment diapir ascending through the mantle wedge. Using a simplified 2‐D circular geometry, we investigate diapir evolution in three scenarios with increasing complexity. In the first two scenarios we consider instantaneous heating of a diapir by thermal diffusion with and without the effect of the latent heat of melting. Then, these simplified calculations are compared to numerical simulations that include melting, melt segregation, and the influence of depletion on the sediment solidus along pressure‐temperature‐time (P‐T‐t) paths appropriate for ascent through the mantle wedge. The high boundary temperature induces a rim of high porosity, into which new melts are focused and then migrate upward. The rim thus acts like an annulus melt channel, while the effect of depletion buffers additional melt production. Solid matrix flow combined with recrystallization of melt pooled near the top of the diapir can result in large gradients in depletion across the diapir. These large depletion gradients can either be preserved if the diapir leaks melt during ascent, or rehomogenized in a sealed diapir. Overall our numerical simulations predict less melt production than the simplified thermal diffusion calculations. Specifically, we show that diapirs whose ascent paths favor melting beneath the volcanic arc will undergo no more than ~40–50% total melting.

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The Role of Volatiles in Reactive Melt Transport in the Asthenosphere

Cited by 130 publications

References 82 publications

Devolatilization of Subducting Slabs, Part II: Volatile Fluxes and Storage

Devolatilization of Subducting Slabs, Part II: Volatile Fluxes and Storage

M2Di: Concise and efficient MATLAB 2‐D Stokes solvers using the Finite Difference Method

Melt Segregation and Depletion During Ascent of Buoyant Diapirs in Subduction Zones

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