b'Education matters limitations of geophysical methods byThe Coolgardie Domain is located withinUniversity of Tasmania, Tasmania simulating a well constrained 2D profilethe Kalgoorlie Terrane, of the YilgarnHonours thesisat depth to understand how structuresCraton, Western Australia. The Domain such as the Mount Isa Fault will translatehas been relatively under studied inJoseph Behan, University of Tasmania: undercover. relation to the other Domains within thePetrophysical and geophysical We focus on the Wonomo Fault, a likelyKalgoorlie Terrane such as the Kambaldacharacterisation of high-grade segment of the Mount Isa Fault. This studyand Ora Banda Domains despite hostingmineralisation at Fosterville Gold Mine, recognised the Wonomo Fault to be thenumerous high-grade gold camps such asVictoria.southern extension of the Mount IsaTindals and Greenfields. Field mapping,Josephs project was kindly supported Fault due to similarities in (1) relationshipgeophysical mapping, litho-geochemistry,by Kirkland Lake Gold, owners of the dividing the Sybella Domain with thedrill core logging and thin section analysisFosterville mine. The two main aims Leichhardt River Domain; (2) geometrywere all utilised to better understand theof the project were: to assess the as a steeply west dipping structure; andarchitecture of the Coolgardie Domainpotential geophysical response of the (3) protracted history of early normaland assess the Au related mineral systemrecently discovered bonanza-grade movement and late reverse reactivation.within the domain. free-gold-in-vein Swan ore system, The fault forms a 1500 m wide high strainA geophysical interpretationand to evaluate the application of zone characterised by intense shearing,constrained by field observationshigh-resolution ground magnetic mylonite development and quartz blows.and measurements as well as drillsurveying for mapping stratigraphy The geophysical response correspondshole data revealed a distinct EWand structures associated with to a linear zone of magnetite destructiontrending architecture that likely formedrefractory wall-rock-hosted gold trending parallel to bedding. An angularas a result of local geometries andmineralisation contained within unconformity between the Leichhardtrheological contrasts between thedisseminated sulphides.Superbasin and the Calvert Superbasin wasgranitic intrusions and greenstone found parallel to the Wonomo Fault withinbelts. Downhole magnetic susceptibilityDensity, magnetic susceptibility, 600 m to the east. The analysis of structuresdata showed an apparent relationshipinductive conductivity, galvanic at depth found responses correspondingbetween Au grade and a high magneticresistivity, induced polarisation and to narrow structures with little offset aresusceptibility response. This relationshipP-wave velocity measurements were typically lost when buried under 500 m ofwas observed in both the Coolgardiecollected on a suite of 270 samples cover while structures juxtaposing units ofand Depot Domains, which arefrom the Swan ore system, its enclosing contrasting petrophysical properties canseparated by the sinistral Kunanallingalteration zone and host sequence. These be interpreted beyond 1000 m and furtherShear Zone. This downhole associationdata were used to create potential field, enhanced using vertical derivative datasets. is likely mapping out a redox boundary,resistivity, induced polarisation and possibly similar to the St Ives camp. seismic reflection forward models of the The ambiguity of interpretationslikely ore-system responses and hence was demonstrated where an angularto recommend appropriate geophysical unconformity produced a similarLitho-geochemistry of the basalts withinexploration strategies.geophysical response to the Wonomoboth the Coolgardie Domain and the Fault. The importance of using fieldDepot Domain showed that the basaltsApproximately 50 line-km of ground mapping to constrain geophysicalbetween the two areas are distinctlymagnetic data were acquired, interpretations and understand thedifferent from each other and thatprocessed and interpreted in an expected lithologies and geometries wasprevious Domain subdivisions of thearea adjacent to a former open pit therefore demonstrated. Kalgoorlie Terrane that included thewhere a large surface diamond drill Depot Domain as part of the Coolgardieprogramme is in progress. Data were Gianni Mercuri, Monash University:Domain are no longer valid. Theacquired at 1 second intervals on Architecture of the Coolgardie Domain:combination of magnetic susceptibility20 m spaced lines. The new ground Implications for Yilgarn mineral systems. measurements, detailed graphicaldata were compared to recently-logging and structural mapping asacquired, high-resolution airborne well as mapping redox relationshipsmagnetic data and the ground data and mineralogy across the Coolgardiereveal significant additional details Domain may prove a vital explorationwhich have been incorporated since it can assist in highlighting zonesinto exploration interpretation and of Au mineralisation. 3D models including potentially mineralised structures some of which The Coolgardie Domain shareswill are being tested by drilling.similarities with other felsic intrusion dominated domains such as theA confidentiality period exists with Southern Cross domain and recognisingKirkland Lake Gold regarding the study these relationships provides insight toresults. Joseph has accepted a 2020 the mineralisation mechanisms in thegraduate position with RioTinto in Coolgardie Domain. Perth.43 PREVIEW DECEMBER 2019'