b'Education matters Potential field modelling on newlyin the Bendigo Zone of the westernintrusions U-shaped magnetic response. acquired gravity data constrained theLachlan Fold Belt. The TarnagullaThe geometry of the intrusion indicates depth of Lake Boga Granite to 7-8 kmGranodiorite displays an intriguingcomponents of sheet-intrusion and and Pyramid Hill Granite to 5-6 km,magnetic response in the shape ofstructural control were also involved which served as minimum deptha U which contains magneticallyin the emplacement of the Tarnagulla constraints on the source of the Durhamfluctuating ring-shaped anomaliesGranodiorite. Furthermore, the Ox High. This and a combination ofimplying that magmatism migratedgeophysical characteristics and path other geological constraints, allowedover time during emplacement. Theof emplacement together suggest that potential field modelling of both gravityMoliagul Granodiorite exists at thefractional crystallization influenced the and magnetic data over the anomaly towestern end of the magnetic U-shapeformation of a relatively mafic, enriched suggest that the geophysical responseand contains ore-mineral occurrencesfinal pulse of magma which resulted in of the Cambrian mafic volcanics areincluding molybdenite, pyrite andthe mineralisation of Mo, Cu and W at Mt responsible for the Durham Ox High atwolframite. The 3D geometry andMoliagul.shallower depths ranging from 14- emplacement history which has led to 15 km, and that these mafic units arethe Tarnagulla Granodiorites unusualKelly Vaughan-Taylor, Macquarie thicker north of the seismic reflectiongeometry is poorly understood. PreviousUniversity: Melting conditions beneath the survey. U-Pb dating constrained the agegeochronology completed for theNewer Volcanics Province from probabilistic for Lake Boga Granite emplacementintrusion was incapable of resolvinginversions of lava compositions and at 3634.9 Ma and Pyramid Hill atthe path of emplacement. This studygeophysical data3713.9 Ma. The Hf isotopic signaturesaims to resolve the geometry and path of these granites suggested thatof emplacement of the Tarnagulla they formed from a two componentGranodiorite. High resolution land-magma mixing process that involvedbased gravity data were acquired at the Cambrian-Ordovician turbidite200 m spacing along 4 profile lines sequences and the Cambrian mafictransecting the intrusion. The new volcanics. The resolved geometriesandgravity data were used in conjunction magma mixing conclusions drawnwith data from previous gravity and in this research have economicaeromagnetic surveys, obtained implications for gold mineralisation,through the online government portal given these mafic rocks have beenGADDS, to form qualitative geophysical interpreted as the source for gold in theinterpretations which characterised four Bendigo Zone. distinct geophysical domains within the pluton. Precise geochronological Mikayla Sambrooks, The University ofanalyses at MIT using the CA-TIMS Melbourne: Geometry and emplacementmethod for U-Pb zircon dating reveals of the Tarnagulla Granodiorite, centrala clockwise path of emplacement fromThe Newer Volcanics Province (NVP) Victoria: Evidence from potentialthe north to the southwest betweenrepresents mainland Australias youngest field modelling and CA-TIMS U-Pb406.620.27 Ma and 399.31.1 Maregion of intraplate volcanism. Despite geochronology analysis and demonstrates a close temporalthe numerous studies that exist on the relationship exists between theorigin and evolution of the volcanic Moliagul and Tarnagulla Granodiorites.centres, the exact mechanism of magma Potential field profile modelling acrossgeneration is heavily debated, with the five traverses that were constrainedexact source composition and melting using measured density and magneticenvironments remaining unclear. A susceptibility values demonstrate thefew models have been developed in an subsurface geometry of the Tarnagullaattempt to explain the magma genesis Granodiorite varies in thickness fromand pathways beneath the NVP however, ~2 km in the north to ~6 km in thethese models tend to focus on either southwest. The models also showgeochemical or geophysical arguments. that the boundaries vary from sub- In this work, we use an integrated horizontal and tapered in the north toapproach using both geochemical and sub-vertical along the southeasterngeophysical observations to explain Igneous intrusions have the potentialmargin and, moreover, that the feedermantle processes. Geochemical data to provide valuable insights intozone likely resides in the southwestfrom the NVP is collated and screened deformation events, crustal architectureat the deepest modelled extent atto obtain a dataset containing samples and composition of the lithosphere~8 km. Precise geochronological datayounger than 2 Ma and representative of that existed at the time of theirwere interpreted alongside the newprimitive melts from peridotitic sources. emplacement. The limitations ofdefined 3D geometry of the TarnagullaA new probabilistic inversion method is studying the geometry of buriedGranodiorite to examine the evolutionapplied to the samples in conjunction intrusions makes it difficult to evaluateof the pluton. The emplacement of thewith a recently developed mantle emplacement mechanisms thatTarnagulla Granodiorite likely involvedmelting model to evaluate the melting controlled their intrusion. The Tarnagullaactive faulting which facilitated theconditions in the mantle; estimates of Granodiorite is an intermediateclockwise movement of a hangingthe composition of the source are also felsic I-type intrusion which waswall over a stationary magma sourceproduced. A separate geophysical model emplaced during the Early Devonianin the footwall, ultimately tracing theof the present-day thermochemical 33 PREVIEW DECEMBER 2020'