Persistent Magma‐Rich Waves Beneath Mid‐Ocean Ridges Explain Long Periodicity on Ocean Floor Fabric

Sim, Susan Elliott

doi:10.1029/2022gl098110

Cited by 3 publications

(2 citation statements)

References 42 publications

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“…Geological observations at SWIR-50.5°E indicate a 300-ky cycle with alternating waxing and waning phases of melt supply ( 28 ), and a cycle-averaged melt flux of 133 km 2 /My is constrained by the geophysically determined crustal thickness ( 43 ) (9.5 km) and the spreading rate (14 km/My) ( 44 ). These cycles could be caused by thermo-chemical heterogeneities in the subridge mantle that modulate magma production and/or by the dynamics of magma transport and collection to the axis, which can be highly unsteady and wave-like ( 41 , 42 , 45 ). This ridge section is currently in what is interpreted as an intermediate stage from waxing to waning ( Fig.…”

Section: Melt Flux Instead Of Spreading Ratementioning

confidence: 99%

Beyond spreading rate: Controls on the thermal regime of mid-ocean ridges

Chen,

Olive,

Cannat

2023

Proc. Natl. Acad. Sci. U.S.A.

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The thermal state of mid-ocean ridges exerts a crucial modulation on seafloor spreading processes that shape ~2/3 of our planet's surface. Standard thermal models treat the ridge axis as a steady-state boundary layer between the hydrosphere and asthenosphere, whose thermal structure primarily reflects the local spreading rate. This framework explains the deepening of axial melt lenses (AMLs)—a proxy for the basaltic solidus isotherm—from ~1 to ~3 km from fast- to intermediate-spreading ridges but fails to account for shallow crustal AMLs documented at slow-ultraslow spreading ridges. Here, we show that these can be explained by a numerical model that decouples the potentially transient ridge magma supply from spreading rate, captures the essential physics of hydrothermal convection, and considers multiple modes of melt emplacement. Our simulations show that melt flux is a better thermal predictor than spreading rate. While multiple combinations of melt/dike emplacement modes, permeability structure, and temporal fluctuations of melt supply can explain shallow crustal AMLs at slow-ultraslow ridges, they all require elevated melt fluxes compared to most ridge sections of comparable spreading rates. This highlights the importance of along-axis melt focusing at slow-ultraslow ridges and sheds light on the natural variability of their thermal regimes.

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Section: Melt Flux Instead Of Spreading Ratementioning

confidence: 99%

Beyond spreading rate: Controls on the thermal regime of mid-ocean ridges

Chen,

Olive,

Cannat

2023

Proc. Natl. Acad. Sci. U.S.A.

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“…These models, however, ignore the contribution from compaction of the solid phase, which is responsible for some dynamic behaviors such as solitary waves (Spiegelman, 1993a). More consistent approaches that include compaction stress assume for example, one‐way coupling (Cerpa et al., 2017; Sim, 2022; Sim et al., 2020; Wilson et al., 2014), in which fluid flow depends on solid flow but does not provide a feedback to solid deformation, or iterative coupling (Gradmann et al., 2012; Morency et al., 2007; Wang et al., 2019), in which solid deformation and fluid migration are coupled but are solved separately. Fully coupled formulations, where the two‐phase system is solved simultaneously, have also been established (Katz, 2008; Keller et al., 2013, 2017; Petrini et al., 2020; Rudge et al., 2011).…”

Section: Introductionmentioning

confidence: 99%

A Three‐Field Formulation for Two‐Phase Flow in Geodynamic Modeling: Toward the Zero‐Porosity Limit

Lu,

May,

Huismans

2023

JGR Solid Earth

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Two‐phase flow, a system where Stokes flow and Darcy flow are coupled, is of great importance in the Earth's interior, such as in subduction zones, mid‐ocean ridges, and hotspots. However, it remains challenging to solve the two‐phase equations accurately in the zero‐porosity limit, for example, when melt is fully frozen below solidus temperature. Here we propose a new three‐field formulation of the two‐phase system, with solid velocity (vs), total pressure (Pt), and fluid pressure (Pf) as unknowns, and present a robust finite‐element implementation, which can be used to solve problems in which domains of both zero porosity and non‐zero porosity are present. The reformulated equations include regularization to avoid singularities and exactly recover to the standard single‐phase incompressible Stokes problem at zero porosity. We verify the correctness of our implementation using the method of manufactured solutions and analytic solutions and demonstrate that we can obtain the expected convergence rates in both space and time. Example experiments, such as self‐compaction, falling block, and mid‐ocean ridge spreading show that this formulation can robustly resolve zero‐ and non‐zero‐porosity domains simultaneously, and can be used for a large range of applications in various geodynamic settings.

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Persistent Heterogeneities in the Oceanic Lithosphere Due To Differential Freezing Beneath Ridges

Sim,

Yu,

Havlin

2024

Geophysical Research Letters

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Oceanic lithosphere, which forms two‐thirds of Earth's surface, is generated at mid‐ocean ridge spreading centers. Yet the internal structure of the lithosphere is not well characterized and often considered to be homogeneous relative to the structure of continental lithosphere. While geophysical observations clearly delineate the crust‐mantle boundary and the lithosphere‐asthenopshere boundary, other seismic anomalies known as mid‐lithosphere discontinuities (MLDs) have been challenging to detect and poorly constrained. Here we present melt transport models applied to the mid‐ocean ridge system that indicate MLDs are a widespread fundamental feature of oceanic lithosphere. In our models, some melt generated from decompression melting is frozen back into the lithosphere, forming a layered refertilization pattern. These refertilized layers are due to the stacked horizontal layering pattern of melt pooling beneath the freezing front. If the recrystallized melt is incorporated into the lithosphere as mafic lenses, the predicted seismic velocity is compatible with observations.

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Persistent Magma‐Rich Waves Beneath Mid‐Ocean Ridges Explain Long Periodicity on Ocean Floor Fabric

Cited by 3 publications

References 42 publications

Beyond spreading rate: Controls on the thermal regime of mid-ocean ridges

Beyond spreading rate: Controls on the thermal regime of mid-ocean ridges

A Three‐Field Formulation for Two‐Phase Flow in Geodynamic Modeling: Toward the Zero‐Porosity Limit

Persistent Heterogeneities in the Oceanic Lithosphere Due To Differential Freezing Beneath Ridges

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