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  • Lower mantle geotherms, flux, and power from incorporating new experimental and theoretical constraints on heat transport properties in an inverse model
Title: Lower mantle geotherms, flux, and power from incorporating new experimental and theoretical constraints on heat transport properties in an inverse model
Abstract. An inverse method is devised to probe Earth's thermalstate without assuming its mineralogy. This constrains thermal conductivity(κ) in the lower mantle (LM) by combining seismologic models of bulkmodulus (B) and pressure (P) vs. depth (z) with a new result, ∂ln(κ) / ∂P ∼ 7.33/BT, and available high temperature (T) data onκ for lengths exceeding millimeters. Considering large samples accounts forthe recently revealed dependence of heat transport properties onlength scale. Applying separation of variables to seismologic ∂B/∂P vs. depth isolates changes with T. The resulting LM dT / dz dependson ∂2B/∂P2 and ∂B/∂T, whichvary little among dense phases. Because seismic ∂B/∂P isdiscontinuous and model dependent ∼ 200 km above the core,unlike the LM, our results are extrapolated through this tiny layer (D′′).Flux and power are calculated from dT / dz for cases of high (oxide) and low(silicate) κ. Geotherm calculations are independent of κ,and thus of LM mineralogy, but require specifying a reference temperature atsome depth: a wide range is considered. Limitations on deep melting are usedto ascertain which of our geotherm, flux, and power curves best representEarth's interior. Except for an oxide composition with miniscule ∂2B/∂P2, the LM heats the core, causing it to melt. Deepheating is attributed to cyclical stresses from > 1000 km dailyand monthly fluctuations of the barycenter inside the LM.  more » « less
Award ID(s):
2122296
PAR ID:
10322114
Author(s) / Creator(s):
Date Published:
Journal Name:
European Journal of Mineralogy
Volume:
34
Issue:
1
ISSN:
1617-4011
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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