Role of random thermal perturbations in the magmatic segmentation of mid-oceanic ridges: Insights from numerical simulations

Sarkar, Shamik; Baruah, Amiya; Dutta, Urmi; Mandal, Nibir

doi:10.1016/j.tecto.2014.08.008

Cited by 9 publications

(17 citation statements)

References 94 publications

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“…Upwellings could result from Rayleigh-Taylor-type instabilities of a low-viscosity melt-rich region that underlies the ridge axis (Whitehead et al (1984); Schouten et al (1985); Kerr and Lister (1988); Parmentier 2018)) or from small-scale convection in the asthenosphere below the axis (Rabinowicz et al (1993); Sparks et al (1993); Rouzo et al (1995); Briais and Rabinowicz (2002)). Upwelling spacing could range from ∼20 km for melt channeling through a crystallizing porous media (Sarkar et al (2014); Mandal et al (2018)) to 100-300 km for asthenospheric convection (Parmentier and Phipps Morgan (1990); Rouzo et al (1995); Sparks et al (1993)). These estimates are, respectively, smaller and larger than the ∼55 km average ridge segment length observed on natural data (Carbotte et al (2015)) and predicted by our experimental scaling.…”

Section: Discussionmentioning

confidence: 99%

Rheological control on the segmentation of the mid-ocean ridges: Laboratory experiments with extension initially perpendicular to the axis

Sibrant

Davaille

Mittelstaedt

2021

Earth and Planetary Science Letters

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Section: Discussionmentioning

confidence: 99%

Rheological control on the segmentation of the mid-ocean ridges: Laboratory experiments with extension initially perpendicular to the axis

Sibrant

Davaille

Mittelstaedt

2021

Earth and Planetary Science Letters

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“…It is now evident that melts start to localize in discrete zones during their ascent that eventually mediates for a heterogeneous magma supply to the ridge axes. Earlier numerical models [74,99] showed melt fraction as a function of spreading rates, suggesting that the melt fraction is substantially reduced from fast-to slow-spreading ridges. Secondly, the melt upwelling processes participate in solidification at the shallow level to form isolated mushy bodies, as reported by many earlier workers [107,108,111].…”

Section: Introductionmentioning

confidence: 93%

“…In submarine systems, the temperature calculated for the critical depth of partial melting cessation constrains the amount of available melt in the subcrustal MC system [80]. However, the melts ascend upward with a complex 3D pattern of their paths, determined by coupled convection-solidification processes [74,99,122]. The volume fraction of melt-crystal aggregates goes up [43,51]as subcrustal magma bodies form at mid-oceanic ridges.…”

Section: Mush Complex In Mor Settingsmentioning

confidence: 99%

Role of mush complex viscosity in modulating axial topography in mid-oceanic ridges

Sen¹,

Sarkar²,

Mandal³

2023

Preprint

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This article exploits the interaction dynamics of the elastic oceanic crust with the underlying mush complexes (MC) to constrain the axial topography of mid-ocean ridges (MORs). The effective viscosity (µ ef f ) of MC beneath MORs is recognized as the crucial factor in modulating their axial high versus flat topography. Based on a two-step viscosity calculation (suspension and solid-melt mixture rheology), we provide a theoretical estimate of µ ef f as a function of melt suspension characteristics (crystal content, polymodality, polydispersity and strain-rate), and its volume fraction in the MC region. We then develop a numerical model to show the control of µ ef f on the axial topography. Using an enthalpy-porosity-based fluid-formulation of uppermost mantle the model implements a one-way fluid-structure interaction (FSI) that transmits viscous forces of the MC region to the overlying upper crust. The limiting non-rifted topographic elevations (-0.06 km to 1.27 km) of model MORs are found to occur in the viscosity range: µ ef f = 10 12 to 10 14 Pa s. The higher-end (10 13 to 10 14 ) Pa s of this spectrum produce axial highs, which are replaced by flat or slightly negative topography as µ ef f ≤ 5 × 10 12 Pa s. We discuss a number of major natural MORs to validate the model findings.

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“…Based on earlier numerical model data and geophysical estimates, the three principal layers of the Tibetan lithosphere: upper/middle crust, lower crust, and mantle lithosphere are assigned varying densities and viscosities (Table 1). We consider a power-law decay function (Sarkar et al, 2014) to represent decreasing viscosities (μ) of model materials with temperature (T):…”

Section: Initial Conditions and Materials Propertiesmentioning

confidence: 99%

Early Miocene Exhumation of High-Pressure Rocks in the Himalaya: A Response to Reduced India-Asia Convergence Velocity

Maiti

Mandal

2021

Front. Earth Sci.

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Low-viscosity channel flow, originating from a melt-weakened mid-crustal layer, is one of the most popular tectonic models to explain the exhumation of deep-seated rocks in the Greater Himalayan Sequence (GHS). The driving mechanism of such channel flow, generally attributed to focused erosion in the mountain front, is still debated, and yet to be resolved. Moreover, the channel flow model cannot explain eclogites in the GHS. In this study, we present a new two-dimensional thermo-mechanical numerical model, based on lubrication dynamics to demonstrate the exhumation process of deep crustal rocks in GHS. The model suggests that a dynamic-pressure drop in the Himalayan wedge, following a large reduction in the India-Asia convergence velocity (15 cm/yr at 50 Ma to nearly 5 cm/yr at ∼22 Ma) localized a fully developed extrusion zone, which controlled the pressure-temperature-time (P-T-t) path of GHS rocks. We show that the wedge extrusion, originated in the lower crust (∼60 km), was initially bounded by two oppositely directed ductile shear zones: the South Tibetan Detachment systems (STDS) at the top and the Higher Himalayan Discontinuity (HHD) at the bottom. With time the bottom shear boundary of the extrusion zone underwent a southward migration, forming the Main Central Thrust (MCT) at ∼17 Ma. Our model successfully reproduces two apparently major paradoxical observations in the Himalaya: syn-convergence extension and inverted metamorphic isograds. Model peak P (10–17 kb) and T (700–820°C) and the exhumation P-T-t path estimated from several Lagrangian points, traveling through the extrusion zone, are largely compatible with the petrological observations in the GHS. The model results account for the observed asymmetric P-T distribution between the MCT and STDS, showing peak P-T values close to the MCT. The lubrication dynamics proposed in this article sheds light on the fast exhumation event (>1 cm/yr) in the most active phase of crustal extrusion (22-17 Ma), followed by a slowed-down event. Finally, our model explains why the extrusion zone became weak in the last 8-10 Ma in the history of India-Asia collision.

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Role of random thermal perturbations in the magmatic segmentation of mid-oceanic ridges: Insights from numerical simulations

Cited by 9 publications

References 94 publications

Rheological control on the segmentation of the mid-ocean ridges: Laboratory experiments with extension initially perpendicular to the axis

Rheological control on the segmentation of the mid-ocean ridges: Laboratory experiments with extension initially perpendicular to the axis

Role of mush complex viscosity in modulating axial topography in mid-oceanic ridges

Early Miocene Exhumation of High-Pressure Rocks in the Himalaya: A Response to Reduced India-Asia Convergence Velocity

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