More Like this

1. The source location of mantle plumes from 3D spherical models of mantle convection

   https://doi.org/10.1016/j.epsl.2017.08.033  

   Li, Mingming; Zhong, Shijie (November 2017, Earth and Planetary Science Letters)
2. Low Melting Temperature of Anhydrous Mantle Materials at the Core‐Mantle Boundary

   https://doi.org/10.1029/2020GL089345  

   Kim, Taehyun; Ko, Byeongkwan; Greenberg, Eran; Prakapenka, Vitali; Shim, Sang‐Heon; Lee, Yongjae (October 2020, Geophysical Research Letters)

   Abstract One of the central challenges in accurately estimating the mantle melting temperature is the sensitivity of the probe for detecting a small amount of melt at the solidus. To address this, we used a multichannel collimator to enhance the diffuse X‐ray scattering from a small amount of melt and probed an eutectic pyrolitic composition to increase the amount of melt at the solidus. Our in situ detection of diffuse scattering from the pyrolitic melt determined an anhydrous melting temperature of 3,302 ± 100 K at 119 ± 6 GPa and 3,430 ± 130 K at the core‐mantle boundary (CMB) conditions, as the upper bound temperature. Our CMB temperature is approximately 700 K lower than the previous estimates, implying much faster secular cooling and higher concentrations of S, C, O, and/or H in the region, and nonlinear, advocating the basal magma ocean hypothesis. 

   more » « less
3. Oceanic plateau of the Hawaiian mantle plume head subducted to the uppermost lower mantle

   https://doi.org/10.1126/science.abd0312  

   Wei, Songqiao Shawn; Shearer, Peter M.; Lithgow-Bertelloni, Carolina; Stixrude, Lars; Tian, Dongdong (November 2020, Science)

   The Hawaiian-Emperor seamount chain that includes the Hawaiian volcanoes was created by the Hawaiian mantle plume. Although the mantle plume hypothesis predicts an oceanic plateau produced by massive decompression melting during the initiation stage of the Hawaiian hot spot, the fate of this plateau is unclear. We discovered a megameter-scale portion of thickened oceanic crust in the uppermost lower mantle west of the Sea of Okhotsk by stacking seismic waveforms ofSSprecursors. We propose that this thick crust represents a major part of the oceanic plateau that was created by the Hawaiian plume head ~100 million years ago and subducted 20 million to 30 million years ago. Our discovery provides temporal and spatial clues of the early history of the Hawaiian plume for future plate reconstructions. 

   more » « less
4. The root to the Galápagos mantle plume on the core-mantle boundary

   https://doi.org/10.26443/seismica.v1i1.197  

   Cottaar, Sanne; Martin, Carl; Li, Zhi; Parai, Rita (October 2022, Seismica)

   Ultra-low velocity zones (ULVZs) are thin anomalous patches on the boundary between the Earth's core and mantle, revealed by their effects on the seismic waves that propagate through them. Here we map a broad ULVZ near the Galápagos hotspot using shear-diffracted waves. Forward modelling assuming a cylindrical shape shows the patch is ~600 km wide, ~20 km high, and its shear velocities are ~25% reduced. The ULVZ is comparable to other broad ULVZs mapped on the core-mantle boundary near Hawaii, Iceland, and Samoa.  Strikingly, all four hotspots where the mantle plume appears rooted by these ‘mega-ULVZs’, show similar anomalous isotopic signatures in He, Ne, and W in their ocean island basalts. This correlation suggests mega-ULVZs might be primordial or caused by interaction with the core, and some material from ULVZs is entrained within the plume. For the Galápagos, the connection implies the plume is offset to the west towards the base of the mantle. 

   more » « less
5. Ductile Deformation of the Lithospheric Mantle

   https://doi.org/10.1146/annurev-earth-031621-063756  

   Warren, Jessica M.; Hansen, Lars N. (May 2023, Annual Review of Earth and Planetary Sciences)

   The strength of lithospheric plates is a central component of plate tectonics, governed by brittle processes in the shallow portion of the plate and ductile behavior in the deeper portion. We review experimental constraints on ductile deformation of olivine, the main mineral in the upper mantle and thus the lithosphere. Olivine deforms by four major mechanisms: low-temperature plasticity, dislocation creep, dislocation-accommodated grain-boundary sliding (GBS), and diffusion-accommodated grain-boundary sliding (diffusion creep). Deformation in most of the lithosphere is dominated by GBS, except in shear zones—in which diffusion creep dominates—and in the brittle-ductile transition—in which low-temperature plasticity may dominate. We find that observations from naturally deformed rocks are consistent with extrapolation of the experimentally constrained olivine flow laws to geological conditions but that geophysical observations predict a weaker lithosphere. The causes of this discrepancy are unresolved but likely reside in the uncertainty surrounding processes in the brittle-ductile transition, at which the lithosphere is strongest. ▪ Ductile deformation of the lithospheric mantle is constrained by experimental data for olivine. ▪ Olivine deforms by four major mechanisms: low-temperature plasticity, dislocation creep, dislocation-accommodated grain-boundary sliding, and diffusion creep. ▪ Observations of naturally deformed rocks are consistent with extrapolation of olivine flow laws from experimental conditions. ▪ Experiments predict stronger lithosphere than geophysical observations, likely due to gaps in constraints on deformation in the brittle-ductile transition. 

   more » « less