b'Education matters older heat flow sites using updatedCameron Adams, The Universityand amphibole. Mafic and ultramafic techniques. ThermoGlobe has beenof Western Australia: Integratingrocks are also commonly aphanitic made available online at Heat-Flow. petrophysical, lithogeochemical, andand comprise fine grained mineral org as an intuitive web applicationmineralogical data to understand thematrices that are too small to identify that allows heat flow practitioners,physical properties of altered maficwith a hand lens. Characterisation climate scientists and all interestedand ultramafic rocks: Implications foris further complicated by alteration, parties easy access to the underlyinggeophysical exploration. which is commonly pervasive and data as well as some useful statisticaltends to erase magmatic textures and aggregations. change rock colour. The result is that visual characterisation of altered mafic The incipience of the magnetotelluricand ultramafic rocks is subjective, method (MT) as an alternative touncertain, and, in many cases, seismic tomography for crustal andinconsistent due to the involvement lithospheric scale applications providesof multiple people logging and researchers with an additional tooldocumenting samples and core.capable of describing the physical properties of the lower crust.A new comprehensively integrated petrophysical-chemical-mineralogical MT is particularly sensitive to bothdatabase was created using diamond composition and temperature;drill cores from four granitoid-however, its predictive capabilitiesgreenstone belts in the Yilgarn are effectively limited by inconsistentCraton including the Plutonic Well Commonly, petrophysical data areMarymia Greenstone Belt, Sandstone results from the laboratory. Iclassified solely by lithotype or lithology. conduct my own laboratoryGreenstone Belt, Minigwal Greenstone This has led to the development ofBelt, and Norseman-Wiluna Greenstone investigation into the effect ofwide-ranging distributions in local in-situ metasomatism on theBelt. Data were collected by making and global petrophysical databasesmany measurements on many samples electrical resistivity of the lower crustthat make geological-geophysical and find no measurable differenceusing many different instruments. interpretations uncertain and unreliable.Furthermore, three constraints were between a fluid-altered eclogiteFurthermore, these distributions are and its direct granulite protolith.imposed on data acquisition, i.e., 1) often multimodal and effected byonly non-destructive tools could be However, diligent comparison withalteration. The reliable characterisation previous experiments reveal a strongused, 2) only tools capable of rapid of rocks (and petrophysical data) ismeasurements could be used, and 3) relationship with iron content amongbest achieved through numerical mafic, lower crustal rocks that canonly portable (and ideally easy to use) interpretation. Quantifying alterationtools could be used. Consequently, be used to provide compositionalis therefore required to place and thermal constraints onmy thesis contemporaneously petrophysical data in correct chemicalreviews data-acquisition practices regional resistivity models. and mineralogical (and geological) for many instruments used in the Finally, I conduct an MT survey overcontexts. minerals exploration industry. In the Mt Gambier sub province inMy thesis purposely investigatessome cases, this also led to reviews southeast Australia and reveal a zonemafic and ultramafic rocks becauseof operational principles (physics), of low-resistivity spatially alignedof their unusual, and often variable,discussions about limitations related with a large step in the lithosphere- petrophysical attributes that are, byto hardware and sampling practices, asthenosphere boundary and crustaland large, associated with alteration.and the development of new ways to structures related to rifting alongFor example, an important focus inidentify and reject atypical samples the southern Australian margin.nickel exploration is the interpretationthat would otherwise complicate Lowest resistivity is found beneathof magnetism associated withthe interpretation of alteration, e.g., the town of Casterton, Victoria, andmagnetite production duringquantifying sample heterogeneity is associated with a small degreeserpentinisation, and, conversely,andoxidation state via pXRF andof partial melt that is expected tomagnetite destruction duringpVis-NIR data.feed both the Mt Gambier and Mttalc-carbonation. QuantifyingA new workflow is presented that Burr Group volcanoes. Magmaticserpentinisation and talc-carbonationaddresses integrated pXRF and pVis-plumbing systems are inferredis therefore crucial to properlyNIR usage from the ground up, i.e., with regards to known basementunderstanding physical propertyinstrument calibration and precision, structures with implications for bothdata that are then used to interpretsample quality, data correction (e.g., gas and geothermal exploration ingeophysical maps. Furthermore, theiron), and alteration and fractionation the region. Additional geophysicalcorrect and reliable characterisation ofcharacterisation. The workflow is then evidence is provided that may indicatemafic and ultramafic rocks is importantapplied to the studied rocks and used to a layer of up to 4 km thickness offor understanding other geoscientificinterpret physical properties and define basaltic magma emplaced withindata, not just petrophysics. However,important trends.the mid-crust. the visual classification and characterisation of mafic and ultramaficCamerons thesis can be accessed via the Sam is currently a postdoc at GFZ Germanrocks is difficult due to the presence ofUniversity of Western Australia research-Research Centre for Geosciences inhard to identify dark, ferromagnesianrepository: https://doi.org/10.26182/Potsdam, Germany. silicate minerals, e.g., olivine, pyroxene,xg61-fa34DECEMBER 2022 PREVIEW 32'