Anomalous mantle at 45°N Mid‐Atlantic Ridge?

Mello, Sidney Luiz de Matos; Cann, J. R.; Fowler, C. M. R.

doi:10.1029/1999jb900267

Cited by 7 publications

(3 citation statements)

References 59 publications

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“…Data along around the Galápagos plume is included as far east and west along the GSC as there is data coverage. For the Azores hot spot, an anomalous mantle regime to the north of the Kurchatov Fracture Zone, previously associated with dense garnet rich mantle [ Mello et al , 1999], limits the length of profile being matched.…”

Section: Symmetry Of Along‐ridge Observablesmentioning

confidence: 99%

“…Various dynamical scenarios have been proposed to account for the apparent asymmetry in many of the observations. Recourse has been made to tilted plumes [ Shen et al , 2002; Yang et al , 2006; Yu et al , 1997], lithospheric damming of outflow [ Vogt and Johnson , 1975], bulk asthenospheric flow [ Chase , 1979; Mertz et al , 1991], ambient mantle compositional anomalies [ Mello et al , 1999] and plume zonation [ Murton et al , 2002]. One reason for this proliferation of dynamical scenarios is that there is no generally accepted global model for plume‐ridge asymmetry.…”

Section: Introductionmentioning

confidence: 99%

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Control of the symmetry of plume‐ridge interaction by spreading ridge geometry

Shorttle

Maclennan

Jones

2010

Geochem Geophys Geosyst

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[1] The Iceland, Galápagos, and Azores plumes have previously been identified as interacting asymmetrically with adjacent spreading centers. We present evidence that the flow fields in these plume heads are radially symmetric, but the geometry of the mid-ocean ridge systems imparts an asymmetric compositional structure on outflowing plume material. First, we quantify the degree of symmetry in geophysical and geochemical observables as a function of plume center location. For each plume, we find that bathymetry and crustal thickness observations can be explained using a single center of symmetry, with these calculated centers coinciding with independently inferred plume center locations. The existence of these centers of symmetry suggests that the flow fields and temperature structure of the three plume heads are radially symmetric. However, no centers of symmetry can be found for the incompatible trace element and isotopic observations. To explain this, we develop a simple kinematic model to predict the effect of mid-ocean ridge geometry on the chemical composition of outflowing plume material. The model assumes radially symmetric outflow from a compositionally heterogeneous plume source, consisting of a depleted mantle component and enriched blebs. These blebs progressively melt out during flow through the melting regions under spreading centers. Asymmetry in trace element and isotopic profiles develops when ridges on either side of the plume center receive material that has been variably depleted according to the length of flow path under the ridge. This model can successfully explain compositional asymmetry around Iceland and Galápagos in terms of an axisymmetric plume interacting with an asymmetric ridge system.Components: 15,700 words, 13 figures, 1 table.

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Section: Symmetry Of Along‐ridge Observablesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Control of the symmetry of plume‐ridge interaction by spreading ridge geometry

Shorttle

Maclennan

Jones

2010

Geochem Geophys Geosyst

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“…Sections, such as the eastern side of the axis between 45°35′N and 45°40′N may be characterized by detachment faulting [ Escartin et al ., ]. Previous studies [ Aumento et al ., ; Keeton and Searle , ; Mello et al ., ; Searle et al ., ] identified a number of different volcanic morphologies in the area and noted that the nature of the AVR changes from narrow, focused volcanism south of 45°33′N to less focused and more tectonized north of 45°33′N [ Searle et al ., ]. The AVR also displays good examples of flat seafloor and volcanic hummocks.…”

Section: Introductionmentioning

confidence: 99%

High‐resolution Remotely Operated Vehicle (ROV) mapping of a slow‐spreading ridge: Mid‐Atlantic Ridge 45°N

Yeo

Searle

2013

Geochem Geophys Geosyst

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[1] Axial volcanic ridges (AVRs) are found on most slow-spreading mid-ocean ridges and are thought to be the main locus of volcanism there. In this study we present high-resolution mapping of a typical, well-defined AVR on the Mid-Atlantic Ridge at 45 N. The AVR is characterized by "hummocky terrain," composed typically of hummocks with pillowed or elongate pillowed flanks with pillowed or lobate lava flow summits, often with small haystacks sitting on their highest points. The AVR is surrounded by several areas of "flat seafloor," composed of lobate and sheet lava flows. The spatial and morphological differences between these areas indicate different eruption processes operating on and off the AVR. Volcanic fissures are found all around and on the AVR, although those with the greatest horizontal displacement are found on the ridge crest and flat seafloor. Clusters of fissures may represent volcanic vents. Extremely detailed comparisons of sediment coverage and examination of contact relations around the AVR suggest that many of the areas of flat seafloor are of a similar age or younger than the hummocky terrain of the AVR. Additionally, all the lavas surveyed have similar degrees of sediment cover, suggesting that the AVR was either built or resurfaced in the same 50 ka time frame as the flat seafloor.

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

Dordevic

Georgen

2016

JGR Solid Earth

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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.

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Anomalous mantle at 45°N Mid‐Atlantic Ridge?

Cited by 7 publications

References 59 publications

Control of the symmetry of plume‐ridge interaction by spreading ridge geometry

Control of the symmetry of plume‐ridge interaction by spreading ridge geometry

High‐resolution Remotely Operated Vehicle (ROV) mapping of a slow‐spreading ridge: Mid‐Atlantic Ridge 45°N

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

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