b'Education matters (TEM) observations to investigate theThomas Ostersen, University ofIn addition to the long period benefits and limitations of conventionalTasmania: Geo-electric structure of theMT surveys, two broadband MT and advanced environmental magneticTasmanian lithosphere from multi-scaletraverses were acquired for shallower techniques for sediments depositedmagnetotelluric data. investigations of the lithosphere under variable redox conditions, and tobeneath western and north western explore the use of LT magnetic propertiesTasmania. These surveys transected for detecting different magnetic particlemajor crustal boundaries between types in marine sediments. EasternPrecambrian Tyennan basement and Mediterranean sediments were selectedthe highly metalliferous Cambrian because they contain complexly varyingto Devonian Dundas-Fossey Trough. mixtures of detrital, biogenic, andTwo-dimensional inverse modelling diagenetically altered magnetic mineralof the traverses broadly agree with assemblages that were deposited underregional 3D modelling derived from varying oxic (organic-poor marls) toAusLAMP MT data, and bring the anoxic (organic-rich sapropels) conditions. geo-electric structure of the upper I demonstrate in this work thatcrust in these regions into sharper conventional bulk magnetic parametersfocus. In the west transect, upper can be used to provide high-resolutionThis project encompassed the Tasmaniancrustal rocks within the Precambrian records of environmental magneticleg of the Australian Lithosphericbasement are considerably less variations, while advanced measurementsArchitecture Magnetotelluric Projectresistive than younger Dundas-provide direct ground-truthing of(AusLAMP) and investigated the geo- Fossey rocks and preserve internal mineral magnetic assemblages thatelectric structure of the Tasmanianheterogeneity potentially imaging enables calculation of magnetizationlithosphere at different scales drivenrelict metamorphic fluid pathways. The contributions of different end members.by three separate newly collected orhighly resistive Dundas-Fossey Trough Thus, a combination of conventionalnewly compiled MT data sets. Longalso contains small-scale low resistivity bulk parameters and advanced magneticperiod MT data were collected over thestructures coincident with crustal-scale techniques can provide detailed recordscourse of a major field campaign acrossfaults observed at surface.from which the meaning of environmentalTasmania and Flinders Island in Bass magnetic signals can be unlocked. In thisStrait, yielding a regionally spacedSix of the AusLAMP long period work, I also demonstrate that LT studiesdata set with periods ranging 5s toMT sites were deployed in central enable clear identification of the extent16000s. Induction arrow patterns ineastern Tasmania surrounding the of the presence of biogenic magnetite,these AusLAMP data agree with earlierLemont geothermal prospect, a superparamagnetic particles, and surficialMT studies in highlighting a regionregion of anomalously high surface maghemitisation of magnetite particles.of low resistivity coincident with, andheat flow that was the subject of Furthermore, new high-resolutionextending southward from the Tamarexploration for geothermal energy magnetic and planktic foraminiferalRiver in northern Tasmania. Three- by KUTh Energy Ltd between 2007 stable oxygen isotope (d18O) proxydimensional inverse modelling of theand 2011. A 255-site broadband records are presented together withAusLAMP data set illuminated theMT data set was acquired by KUTh published geochemical data from easterngeo-electric structure of the entire islandEnergy Ltd at Lemont between 2008 Mediterranean sediments to discuss thespanning the upper-crust through toand 2010 which culminated in the causes of increased dust inputs from thelithospheric mantle depth range (~1inversion of a 3D resistivity model of Sahara Desert across the mid-Pleistocene0km to ~100 km), revealing anomalouslythe area. The newly acquired long Transition (MPT). After assessinglow electrical resistivities along majorperiod MT data, together with the hypotheses for increased Saharan dustterrain boundaries in the mid- to upper- existing broadband data, presented inputs across the MPT, including increasingcrust likely resulting from conductivean opportunity to re-model the source-area aridity due to reducedmineral phases and pore fluids in shearLemont MT data set. This modelling precipitation, expanding dust source areas,zones. At deeper levels in the model, inexercise improved on the previous and atmospheric CO2 reduction that ledthe mid- to lower-crust, clear differences3D resistivity model by increasing the to decreased vegetation and soil cohesion,in the electrical character betweenhorizontal resolution of the model I find that increasing climate extremesgeologically distinct Eastern and Westernspace, and incorporating the AusLAMP boosted wind-blown dust productionTasmanian terrains emerge, with the3D model as a priori model structure. and emissions. This is important becauseEastern terrain returning consistentlyTogether with different inversion the resultant aeolian aerosols play ahigher resistivities likely reflecting theapproaches to static shift effects major role in both the radiative balancedepletion of conductive mineral phasesin the data, these improvements of climate and biogeochemical cyclesfollowing voluminous melt extraction inyielded significant differences in in areas where the dust settles. Thisthe Devonian. Electrical heterogeneitysubsurface resistivity structure relative work provides valuable insights into thein the Western terrain includes regionsto the previous model, with the application of conventional bulk andof anomalously low resistivities thatupdated model containing more detail. more advanced component-specificcontinue from the lower-crust to theThe distribution of low resistivity zones methods in identifying mineral magneticlithospheric mantle and are interpreted asin the updated model agrees with assemblages in palaeoceanographic andbeing due to subduction-related mantleinferred subsurface fault structures palaeoenvironmental reconstructions, andmetasomatism potentially associatedthought to represent porous conduits in explaining increased Saharan dustinesswith the intrusion of ubiquitous Jurassicfor fluids radiogenically heated by across the MPT. dolerites. underlying Devonian granitoids.DECEMBER 2021 PREVIEW 34'