Dynamics of plume–triple junction interaction: Results from a series of three‐dimensional numerical models and implications for the formation of oceanic plateaus

Abstract

Mantle plumes rising in the vicinity of mid-ocean ridges often generate anomalies in melt production and seafloor depth. This study investigates the dynamical interactions between a mantle plume and a ridge-ridge-ridge triple junction, using a parameter space approach and a suite of steady state, three-dimensional finite element numerical models. The top domain boundary is composed of three diverging plates, with each assigned half-spreading rates with respect to a fixed triple junction point. The bottom boundary is kept at a constant temperature of 1350°C except where a two-dimensional, Gaussian-shaped thermal anomaly simulating a plume is imposed. Models vary plume diameter, plume location, the viscosity contrast between plume and ambient mantle material, and the use of dehydration rheology in calculating viscosity. Importantly, the model results quantify how plume-related anomalies in mantle temperature pattern, seafloor depth, and crustal thickness depend on the specific set of parameters.To provide an example, one way of assessing the effect of conduit position is to calculate normalized area, defined to be the spatial dispersion of a given plume at specific depth (here selected to be 50 km) divided by the area occupied by the same plume when it is located under the triple junction. For one particular case modeled where the plume is centered in an intraplate position 100 km from the triple junction, normalized area is just 55%. Overall, these models provide a framework for better understanding plateau formation at triple junctions in the natural setting and a tool for constraining subsurface geodynamical processes and plume properties.Previous authors have established scaling laws for plume-ridge dynamical interaction and tested them against experimental data obtained either in the lab using corn syrup tanks [e.g., Feighner and Richards, 1995] or using solutions from numerical models [Ribe et al.

Afar triple junction triggered by plume-assisted bi-directional continental break-up

“…1 ). In contrast to previous studies that use an arbitrary pre-defined triple junction geometry 4 , 42 , we impose no pre-existing structuration within the crust or lithospheric mantle in order to investigate the spontaneous initiation of a divergent triple junction in response to the simultaneous action of the mantle plume and far-field extensional stresses. We simulate tectonic forcing by applying a constant divergent velocity normal to the “eastern” and “western” model boundaries combined with laterally varying pull along the northern side of the model (Supplementary Fig.…”

“…Therefore, the initiation and evolution of R-R-R triple junctions likely involves more complex boundary conditions, possibly bi-directional 5 . R-R-R triple junctions have been modelled for relatively simple conditions of oceanic plate break-up 4 , 5 , but their initiation in continental lithosphere under realistic multi-directional boundary conditions remains unaddressed.…”

Formation and evolution of Shatsky Rise oceanic plateau: Insights from IODP Expedition 324 and recent geophysical cruises

“…It may well be that upwelling -whatever the depth of origin -is entrained into sub-spreading ridge upwelling in the asthenosphere (Fig. 20), which can be strong beneath triple junctions because of the surface divergence (Georgen and Lin, 2002;Georgen 2008;Dordevic and Georgen, 2016). Massif were emplaced in two pulses at least 3 Myr apart.…”

Analog and Numerical Modeling of Rift‐Rift‐Rift Triple Junctions

“…Concerning numerical models, a few works simulated the interaction between RRR triple junction and mantle plumes, testing the specific role of plumes on broad strain evolution and providing information on the crustal and asthenosphere dynamics, rather than focusing on the surface structural architecture, while others mainly focused on the understanding of magma paths below triple junctions and the role of mantle plumes (e.g., Dordevic & Georgen, 2016; Georgen & Lin, 2002; Karaoğlu et al., 2016; Koptev et al., 2018), therefore without investigating the structural patter evolution, as our models do. Other works demonstrated that transient quadruple and triple junctions formed by continental breakup, are gradually converted into stable oceanic triple junctions (Gerya & Burov, 2018).…”