b'Education matters intensity of crustal extension, thethat heat production at formation forSamuel Jennings, University of Adelaide: size of continental back arc basins,different rock types has been relativelyNature of the lower crustand the modes of subsequent basinconstant through time except for the inversion. early Archean to2.7 Ga. I suggest theheat productionage pattern does not Matthew Gard, University of Adelaide:significantly reflect the influences of Constraints on the thermal state oferosion, secular cooling, depletion, or the continental lithosphere the supercontinent cycle as suggested by some previous studies, but instead either reflects a shift in the bulk composition of the crust or evidence for bias in the rock record due to thermal stability.Geophysical proxies provide additional constraints on the crustal thermal state. I have developed a global Curie Depth model from the latest satellite-derived lithospheric magnetic model using the equivalent source magnetic dipole method. Forward modelling was conducted to simulate the observed lithospheric magnetic field. Our updated The thermal state of the lithospheremethodology involves additional vectorKnowledge of the compositional and is an important driver of manycomponents utilised in the forwardthermal structure of the lower crust physical and chemical processesmodelling calculations, a differingis crucial for developing geodynamic, within the Earth. Understandinglong-wavelength model, and inclusionthermodynamic, chemical and the distributions of heat flow andof a spatially variable magneticstructural models of the earth. Our radiogenic heat production providessusceptibility estimate. Resultantcurrent understanding of deep an important constraint on lithosphericcontinental Curie depth estimates showcrustal processes is predominantly thermal models. By some estimatesgood agreement with observed heatbased on seismic modelling and the nearly 40% of continental heat flowflow observations and provide furtherultimately rare surficial occurrence is produced by radioactive decay inevidence that Curie depth estimates canof lower crustal analogues in the the crust, however the distributionassist in estimates of the thermal stateform of xenoliths or granulite of heat producing elements is poorlyof the lithosphere. terranes. Determination of crustal constrained. Creating robust modelsgeotherms, upon which all physical of radiogenic heat production requiresFinally, I assess various heat flowprocesses rely, are plagued by quality an understanding of its naturalmodels for Antarctica derived fromassurance and inaccessibility of variability. The creation of a globalgeophysical proxies. Extrapolationexisting surface heat flow estimates whole-rock geochemical databasefrom isotherm estimates at depthas well as uncertainties inherent in provides a framework for discussingrequire models of heat productionpredicting thermal conductivity and global distributions of thermaland thermal conductivity to modelheat production at depth.parameters. I have collated over onesurface heat flow. Differences in models can have non-trivial influencesIn this thesis, I first establish an million digital rock entries with a rangeon the results produced. Quantifyingimproved method for estimating of sample data including major andthe uncertainty associated with thesethermal conductivity at depth based trace element concentrations, isotopicthermal parameters is also critical foron the chemical compositions across ratios, and other metadata.understanding and interpreting thea wide range of plutonic, igneous Associated naming schemaheat flow solutions. I propose a setrocks. I relate the resulting model and physical parameter estimatesof models derived from whole-rockto estimates of seismic P-wave are also computed in a standardisedgeochemical data and guided byvelocity and density which allows for manner, including radiogenic heatcompositional studies of the crust.prediction of thermal conductivity production. Uncertainties associated with this modelwhere rock samples are inaccessible. I then present a new model forare estimated via the Monte CarloI supplement this new predictive continental igneous heat productionmethod. I show that applying modelsmodel for thermal conductivity with from4 Ga to the present using aguided by global insights providesa restructuring of the global heat flownovel silica-normalised igneousa reasonable fit to the Antarcticadatabase, which allows for improved data set and compare that model tocontinent, and a method of estimatingassessment of quality and better previous discussions of granitic anduncertainty in thermal parameters forinterpretation of the underlying data. sedimentary trends in the literature.regions lacking basement geologyThe new ThermoGlobe database Crude normalisation for compositionconstraints. includes direct relationships to raw indicates lithological control is thethermal data such as temperature, dominant factor on heat production afterMatt currently works at Geoscienceconductivity and heat production, the influence of decay is removed. I findAustralia in geomagnetism. which allows for recalculation of 31 PREVIEW DECEMBER 2022'