TY - JOUR
T1 - The influence of deep mantle compositional heterogeneity on Earth's thermal evolution
AU - Li, Mingming
AU - McNamara, Allen K.
N1 - Funding Information:
This work was funded by NSF grants EAR-1338810 and EAR-1722623 .
Funding Information:
This work was funded by NSF grants EAR-1338810 and EAR-1722623.
Publisher Copyright:
© 2018 Elsevier B.V.
PY - 2018/10/15
Y1 - 2018/10/15
N2 - The seismically-observed large low shear velocity provinces in the Earth's lowermost mantle have been hypothesized to be caused by thermochemical piles of compositionally distinct, more-primitive material which may be remnants of Earth's early differentiation. However, one critical question is how the Earth's thermal evolution is affected by the long-term presence of the large-scale compositional heterogeneity in the lowermost mantle. Here, we perform geodynamical calculations to investigate the time evolution of the morphology of large-scale compositional heterogeneity and its influence on the Earth's long-term thermal evolution. Our results show that a global layer of intrinsically dense material in the lowermost mantle significantly suppresses the CMB heat flux, which leads to faster cooling of the background mantle relative to an isochemical mantle. As the background mantle cools, the intrinsically dense material is gradually pushed into isolated thermochemical piles by cold downwellings. The size of the piles also decreases with time due to entraining of pile material into the background mantle. The morphologic change of the accumulations of intrinsic dense material eventually causes a gradual increase of CMB heat flux, which significantly reduces the cooling rate of Earth's mantle.
AB - The seismically-observed large low shear velocity provinces in the Earth's lowermost mantle have been hypothesized to be caused by thermochemical piles of compositionally distinct, more-primitive material which may be remnants of Earth's early differentiation. However, one critical question is how the Earth's thermal evolution is affected by the long-term presence of the large-scale compositional heterogeneity in the lowermost mantle. Here, we perform geodynamical calculations to investigate the time evolution of the morphology of large-scale compositional heterogeneity and its influence on the Earth's long-term thermal evolution. Our results show that a global layer of intrinsically dense material in the lowermost mantle significantly suppresses the CMB heat flux, which leads to faster cooling of the background mantle relative to an isochemical mantle. As the background mantle cools, the intrinsically dense material is gradually pushed into isolated thermochemical piles by cold downwellings. The size of the piles also decreases with time due to entraining of pile material into the background mantle. The morphologic change of the accumulations of intrinsic dense material eventually causes a gradual increase of CMB heat flux, which significantly reduces the cooling rate of Earth's mantle.
KW - compositional heterogeneity
KW - lowermost mantle
KW - thermal evolution
KW - thermochemical piles
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U2 - 10.1016/j.epsl.2018.08.009
DO - 10.1016/j.epsl.2018.08.009
M3 - Article
AN - SCOPUS:85051472072
SN - 0012-821X
VL - 500
SP - 86
EP - 96
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
ER -