Partial melting of stagnant oceanic lithosphere in the mantle transition zone and its geophysical implications

Long-lived, widespread intraplate volcanism without age progression is one of the most controversial features of plate tectonics. Previously proposed edge-driven convection, asthenospheric shear, and lithospheric detachment fail to explain the ~5000-km-wide intraplate volcanic province from eastern Australia to Zealandia. We model the subducted slab volume over 100 million years and find that slab flux drives volcanic eruption frequency, indicating stimulation of an enriched mantle transition zone reservoir. Volcanic isotope geochemistry allows us to distinguish a high-μ (HIMU) reservoir [>1 billion years (Ga) old] in the slab-poor south, from a northern EM1/EM2 reservoir, reflecting a more recent voluminous influx of oceanic lithosphere into the mantle transition zone. We provide a unified theory linking plate boundary and slab volume reconstructions to upper mantle reservoirs and intraplate volcano geochemistry.

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Intraplate volcanism triggered by bursts in slab flux

10.5194/egusphere-egu21-6857 ◽

2021 ◽

Author(s):

Ben Mather ◽

Dietmar Muller ◽

Maria Seton ◽

Saskia Ruttor ◽

Oliver Nebel ◽

...

Keyword(s):

Transition Zone ◽

Plate Tectonics ◽

Isotope Geochemistry ◽

Plate Boundary ◽

Oceanic Lithosphere ◽

Mantle Transition Zone ◽

Age Progression ◽

Intraplate Volcanism ◽

Eastern Australia ◽

Mafic Volcanism

Long-lived, widespread intraplate volcanism without age progression is one of the most controversial features of plate tectonics. The eastern margin of Australia and Zealandia has experienced extensive mafic volcanism over the last 100 million years. A plume origin has been proposed for three distinct chains of volcanoes, however, the majority of eruptions exhibit no clear age progression. Previously proposed edge-driven convection, asthenospheric shear, and lithospheric detachment fail to explain the non age-progressive eruptions across the ~5000 km wide intraplate volcanic province from Eastern Australia to Zealandia. We model the subducted slab volume over 100 million years and find that slab flux drives volcanic eruption frequency, indicating stimulation of an enriched mantle transition zone reservoir. Volcanic isotope geochemistry allows us to distinguish a HIMU reservoir (>1 Ga old) in the slab-poor south, from a northern EM1/EM2 reservoir, reflecting a more recent voluminous influx of oceanic lithosphere into the mantle transition zone. We provide a unified theory linking plate boundary and slab volume reconstructions to upper mantle reservoirs and intraplate volcano geochemistry.

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Deep Slab folding and the deformation of the Persian domain

10.5194/egusphere-egu2020-17835 ◽

2020 ◽

Author(s):

Alexandre Boutoux ◽

Arthur Briaud ◽

Claudio Faccenna ◽

Paolo Ballato ◽

Federico Rossetti ◽

...

Keyword(s):

Numerical Model ◽

Transition Zone ◽

Cross Sections ◽

Structural Evolution ◽

Oceanic Lithosphere ◽

Mantle Transition Zone ◽

Plate Deformation ◽

Flooding Event ◽

Back Arc ◽

Subduction System

<ul><li>To unravel the Neotethys subduction history and the evolution of the slab morphology at depth since the mid-Cretaceous, we produced a synthesis of the main events affecting the Persian domain. This synthesis is focused on the upper and lower plates (i.e. the Persian and the Neotethys ocean, respectively) of the subduction system and is based on the compilation of available structural, geochemical and geochronological data. Overall, this compilation allows exploring the structural evolution of the Persian domain and the Neotethys oceanic lithosphere on map view and along selected cross-sections.</li> <li>Furthermore, we performed a 2D single-sided numerical model where we explored the slab behavior at depth and its influence on upper plate deformation. The model suggests that episodic deformation is driven by the folding slab behavior at the mantle transition zone. We combine our data and numerical model into a conceptual scenario to overcome the complexity of the kinematics of the Neotethys slab since the Early Cretaceous. Our modeling approach shows that back-arcs opening and associated extensional deformation are driven by the roll-back of the folded slab into the mantle transition zone. In contrast, back-arc closure and upper plate shortening are triggered by the roll-over of the folding slab. Finally, we associate the widespread, upper plate, Early Miocene marine flooding event to the Neotethys slab avalanche into the lower mantle.</li> </ul>

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Behaviors of Wet Plume Controlled by Olivine-Wadsleyite Phase Transition and Water Distribution

10.5194/egusphere-egu21-1944 ◽

2021 ◽

Author(s):

Hyunseong Kim ◽

Youngjun Lee ◽

Doyoung Kim ◽

Changyeol Lee

Keyword(s):

Phase Transition ◽

Partial Melting ◽

Transition Zone ◽

Korean Peninsula ◽

Northeast China ◽

Bound Water ◽

Mantle Transition Zone ◽

Hydrated Layer ◽

Geochemical Studies ◽

Stagnant Slab

Quaternary Intraplate volcanoes are sparsely distributed in Northeast Asia including Northeast China and Korean Peninsula and roles of the stagnant Pacific plate in the volcanoes have been studied. Recent geochemical studies suggest that the hydrated mantle in the mantle transition zone was incorporated in the wet plumes that were generated from the hydrated layer atop the stagnant slab, and the ascending wet plumes experienced partial melting in the shallow asthenosphere. To quantitatively evaluate the incorporation of the mantle in the transition zone into the wet plumes and their partial melting in the asthenosphere, we conducted a series of two-dimensional thermochemical numerical models by including the olivine-wadsleyite phase transition at the 410km discontinuity. The buoyancy is controlled by temperature, bound-water content and mineral phase. Viscosity reduction by the bound-water is added to the temperature-dependent viscosity. Particle tracers are used to track the incorporation of the mantle in the transition zone into the wet plumes. We vary the Clapeyron slope of the phase transition and water distributions in the mantle transition zone and hydrated layer of the stagnant slab to evaluate their effects on the behavior of the wet plumes. Results show that multiple wet plumes generated from atop the stagnant slab incorporate the hydrated mantle in the transition zone. Due to the endothermic phase transition at the 410 km discontinuity, the ascending wet plumes are retarded and laterally migrated beneath the 410 km discontinuity for several million years, and enter the overlying asthenosphere as merged large wet plumes. The ascending merged wet plumes laterally spread beneath the thermal lithosphere and experience partial melting, consistent with the interpretation based on the geochemical studies. The spacing of the merged wet plumes (~440 km) caused by the phase transition at the 410 km discontinuity is consistent with the sparse volcano distribution in Northeast China and Korean Peninsula.

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Theoretical modeling of the regular olivine intergrowths in the mimetic paramorphosis after ringwoodite and wadsleyite

Moscow University Bulletin. Series 4. Geology ◽

10.33623/0579-9406-2018-4-3-12 ◽

2018 ◽

pp. 3-12

Author(s):

B. B. Shkursky

Keyword(s):

Transition Zone ◽

Theoretical Modeling ◽

Mantle Transition Zone ◽

Misorientation Angles

Theoretical modeling of regular olivine grains misorientations in mimetic paramorphoses after ringwoodite and wadsleyite, the formation of which during the ascension of matter from the Mantle Transition Zone is expected, has been carried out. The coordinates of the misorientation axes and the misorientation angles, characterizing 10 operations of alignment in the pair intergrowths of olivine grains, eight of which are twins, are calculated. Possible conditions for the formation of mimetic paramorphoses predicted here, and the chances of their persistence are discussed. The calculated orientations are compared with the known twinning laws of olivine.

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