Seismic constraints on temperature of the Australian uppermost mantle

Saskia Goes

Department of Earth Sciences and Engineering
Imperial College London
London, SW7 2AZ, United Kingdom

Frederik J Simons

Department of Earth Sciences
University College London
London, WC1E 6BT, United Kingdom

Kazunori Yoshizawa

Division of Earth and Planetary Sciences
Hokkaido University
Sapporo, Japan

Abstract

We derive estimates of temperature of the Australian continental mantle between 80 and 350 km depth from two published S-velocity models. Lithospheric temperatures range over about 1000°C, with a large-scale correlation between temperature and tectonic age. In detail however, variations ranging from 200 and 700°C occur within each tectonic province. At the current seismic resolution, strictly Proterozoic and Archean blocks do not have substantially different temperatures, nor does the Phanerozoic lithosphere east and west of the Tasman line. Temperatures close to an average (moist) MORB source mantle solidus characterize the eastern seaboard and its offshore. Differences between the temperatures derived from the two velocity models illustrate the importance of well-constrained absolute velocities and gradients for physical interpretation. The large range of lithospheric temperatures cannot be explained solely with documented variability in crustal heat production, but requires significant variations in mantle heat flow as well.

Figures

1. Figure 01 Tectonics, geotherm locations, surface heat flow, and seismically derived temperature estimates
   
2. Figure 02 Comparison of seismically derived temperature estimates between both seismic models
   
3. Figure 03 Average geotherms for large-scale, and more detailed tectonic subdivisions
   
4. Figure 04 Comparison of seismic geotherms with surface heat flow and geotherms from geothermobarometry
   
5. Figure 05 Steady-state conductive geotherms for fixed mantle heat-flow values and a range of crustal heat production rates
   

Frederik Simons