2:45 PM - 3:00 PM
[S21-1-05] Lithospheric heat production: calculating mantle heat flow from asthenospheric shear velocity variations
Estimates of heat production in the continental crust are derived from a combination of petrological, geochemical, and geophysical constraints, with some models predicting variability in the abundance and distribution of the heat-producing elements (HPE: U, Th, K) in the lower and middle layers (from correlation of SiO2 and VP), and constant HPE concentrations in the upper crustal layer. Geophysical models (e.g., CRUST 1.0) define layer density, thickness, and VP variation on a 1x1 degree grid. Geochemical and geophysical models are used to calculate the surface heat flow, assuming a Moho heat flux, with up to 100% difference between observed and predicted surface heat flows. Inversion of crustal heat production from surface heat flow gives non-unique solutions due to a poorly constrained Moho heat flux. We explore how mantle heat flux variations calculated from seismic constraints affect the agreement between observed surface heat flux and that predicted by models of continental crust.
Asthenosphere temperatures are derived from dVs/dT relationships, global Vs tomographic models, LAB depth models, mantle potential temperature and adiabat. LAB temperature is given as the intersection of the mantle adiabat with the LAB. Using this LAB temperature, mantle adiabat, and estimates of mantle thermal conductivity, we calculate the LAB heat flux on a 1x1 degree grid. Subtracting the predicted sub-LAB heat flux from the observed surface heat flow for Archean and Proterozoic crust gives a heat production in each lithospheric column. We then calculate the heat production in the continental crust for each column by removing heat production in the lithospheric mantle, as determined from a xenolith-derived geotherm. We evaluate the implications for crustal heat production due to various model parameters, including biases in the seismic LAB determinations, use of different tomographic models, and assumptions about mantle potential temperature and dVs/dT relationships.
Asthenosphere temperatures are derived from dVs/dT relationships, global Vs tomographic models, LAB depth models, mantle potential temperature and adiabat. LAB temperature is given as the intersection of the mantle adiabat with the LAB. Using this LAB temperature, mantle adiabat, and estimates of mantle thermal conductivity, we calculate the LAB heat flux on a 1x1 degree grid. Subtracting the predicted sub-LAB heat flux from the observed surface heat flow for Archean and Proterozoic crust gives a heat production in each lithospheric column. We then calculate the heat production in the continental crust for each column by removing heat production in the lithospheric mantle, as determined from a xenolith-derived geotherm. We evaluate the implications for crustal heat production due to various model parameters, including biases in the seismic LAB determinations, use of different tomographic models, and assumptions about mantle potential temperature and dVs/dT relationships.