Production, pathways and budgets of melts in mid-ocean ridges: An enthalpy based thermo-mechanical model

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

“…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.…”

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

“…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].…”

“…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.…”

“…Many mid-ocean ridges (MORs) evolve with complex 3D axial topography, which is hard to explain with standard tectonic models. Their spatially varying axial topography, such as high, flat or valley, is generally attributed to the spreading rate [106,110], the magma availability [59,74,108], in a particular ridge-segment, and upper crustal faulting [12]. However, these contrasting axial morphologies are often found in MORs, e.g., South-East Indian Ridge (SEIR), where the spreading rate shows practically no variations [16], and ultra-slow South-West Indian Ridges (SWIR) displaying typical axial valley topography, where they have large magma availability [55].…”

Cold Plumes Initiated by Rayleigh‐Taylor Instabilities in Subduction Zones, and Their Characteristic Volcanic Distributions: The Role of Slab Dip

“…However, a number of key questions, especially on the melt transport mechanisms, are yet to be resolved. For example, there is still debate on whether partial melts ascend by forming porosity channels, as observed beneath mid‐ocean ridges (Liang et al, 2010; Mandal et al, 2018), and if so, what can be their pathways patterns, or are channels formed by fracturing of the mantle rocks? Several recent studies suggest cold plume formation as a potential mechanism for the upward advection of partially molten materials in the mantle wedge (Codillo et al, 2018; Gerya & Yuen, 2003; Zhu et al, 2009).…”