TY - JOUR
T1 - The Formation of Hot Thermal Anomalies in Cold Subduction-Influenced Regions of Earth's Lowermost Mantle
AU - Li, Mingming
N1 - Funding Information:
I am grateful for the constructive reviews from Maxim Ballmer and Rhodri Davies, and discussions with Edward Garnero. Geodynamic models were performed on the Agave cluster at Arizona State University. Figures 1 , 2 , 5 , and 8–12 are plotted with the Generic Mapping Tools (GMT, www.soest.hawaii.edu/gmt/ ), and Figures 3 , 4 , 6 , 7 , and 13 are plotted using Paraview ( https://www.paraview.org/ ). The 15 shear wave seismic tomography models shown in Figure 2 are downloaded from SubMachine ( http://www.earth.ox.ac.uk/~smachine/cgi/index.php ). This work is supported by NSF grants EAR‐1849949 and EAR‐1855624. There is no conflict of interest.
Funding Information:
I am grateful for the constructive reviews from Maxim Ballmer and Rhodri Davies, and discussions with Edward Garnero. Geodynamic models were performed on the Agave cluster at Arizona State University. Figures?1, 2, 5, and 8?12 are plotted with the Generic Mapping Tools (GMT, www.soest.hawaii.edu/gmt/), and Figures?3, 4, 6, 7, and 13 are plotted using Paraview (https://www.paraview.org/). The 15 shear wave seismic tomography models shown in Figure?2 are downloaded from SubMachine (http://www.earth.ox.ac.uk/~smachine/cgi/index.php). This work is supported by NSF grants EAR-1849949 and EAR-1855624. There is no conflict of interest.
Publisher Copyright:
©2020. American Geophysical Union. All Rights Reserved.
PY - 2020/6/1
Y1 - 2020/6/1
N2 - The Earth's lowermost mantle is characterized by two large low shear velocity provinces (LLSVPs). The regions outside the LLSVPs have been suggested to be strongly influenced by subducted slabs and, therefore, much colder than the LLSVPs. However, localized low-velocity seismic anomalies have been detected in the subduction-influenced regions, whose origin remains unclear. Here, three-dimensional geodynamic calculations are performed, and they show that linear, ridge-like hot thermal anomalies, or thermal ridges, form in the relatively cold, downwelling regions of the lowermost mantle. Like the formation of Richter rolls due to sublithosphere small-scale convection (SSC), the thermal ridges form as a result of SSC from the basal thermal boundary layer and they extend in directions parallel to the surrounding mantle flow. The formation of thermal ridges in subduction regions of the lowermost mantle is very sensitive to the thermal structures of the subducted materials, and thermal heterogeneities brought to the bottom of the mantle by subducting slabs greatly promote the formation of thermal ridges. The formation of thermal ridges is also facilitated by the increase of core-mantle boundary heat flux and vigor of lowermost mantle convection. The thermal ridges may explain the low-velocity seismic anomalies outside of the LLSVPs in the lowermost mantle. The results suggest that the relatively cold, subduction-influenced regions of the Earth's lowermost mantle may contain localized hot anomalies.
AB - The Earth's lowermost mantle is characterized by two large low shear velocity provinces (LLSVPs). The regions outside the LLSVPs have been suggested to be strongly influenced by subducted slabs and, therefore, much colder than the LLSVPs. However, localized low-velocity seismic anomalies have been detected in the subduction-influenced regions, whose origin remains unclear. Here, three-dimensional geodynamic calculations are performed, and they show that linear, ridge-like hot thermal anomalies, or thermal ridges, form in the relatively cold, downwelling regions of the lowermost mantle. Like the formation of Richter rolls due to sublithosphere small-scale convection (SSC), the thermal ridges form as a result of SSC from the basal thermal boundary layer and they extend in directions parallel to the surrounding mantle flow. The formation of thermal ridges in subduction regions of the lowermost mantle is very sensitive to the thermal structures of the subducted materials, and thermal heterogeneities brought to the bottom of the mantle by subducting slabs greatly promote the formation of thermal ridges. The formation of thermal ridges is also facilitated by the increase of core-mantle boundary heat flux and vigor of lowermost mantle convection. The thermal ridges may explain the low-velocity seismic anomalies outside of the LLSVPs in the lowermost mantle. The results suggest that the relatively cold, subduction-influenced regions of the Earth's lowermost mantle may contain localized hot anomalies.
KW - LLSVP
KW - hot thermal anomalies
KW - low-velocity structures
KW - lowermost mantle
KW - mantle plumes
KW - subducting slabs
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U2 - 10.1029/2019JB019312
DO - 10.1029/2019JB019312
M3 - Article
AN - SCOPUS:85087084167
VL - 125
JO - Journal of Geophysical Research: Atmospheres
JF - Journal of Geophysical Research: Atmospheres
SN - 2169-897X
IS - 6
M1 - e2019JB019312
ER -