b'AEGC 2023Short abstractsduring the Cenozoic and five independent proxies for crustalstudy in the Northern Territory is re-examined in the light of thickening of the central Andes during the Cenozoic. We analysenew technology.how different plate motion and crustal thickening modelsInterpretation of aeromagnetic data in areas of limited outcrop correlate with each other. Then, using time series analysis, weuse data enhancement to support accurate positioning quantify the cause-and-effect nature of plate tectonic motionof geological boundaries and magnetic sources. Where and continental thickening processes. We are able discernno outcrop calibration exists, magnetic sources must be which plate motion and which continental uplift models arecharacterised by physical parameters relating to their form, most appropriate to incorporate into further analysis for spatio- depth and relative magnetisation. The final stage of the temporal mapping and prediction of PCDs. interpretation process is to apply geological reasoning, in the context of the area being interpreted, to deduce the rock Palaeostress inversion for mineral exploration; thetypes causing the magnetic responses and the structural Tolukuma test. relationships of the lithological units.In 1997, limitations of digital computing, and languages Robert Findlay restricted many developments. Whilst technology has advanced The remarkably rich Tolukuma gold mine of Central Province,in the intervening 25 years, cutting corners remains rampant PNG, lies on the southern flank of the deeply eroded, 34 kmin the industry. The hope that somehow the technology by 24 km, Pliocene (4.8 Ma; U/Pb zircon dating, unpublishedmajors developing and deploying on the cloud, will magically company report Newmont, 1989) andesitic Boundary Volcano.overcome the deficiencies and rigour in the application of the In the mined area the mapped distribution of major faults andcorrect physics, material science, mineralogy, and structural veins follows the overall geometry of the well-known Riedelgeology, is exposed. Aspects of the 1997 methods are still shear system. The mined ore bodies occur predominantlyelusive to ML and AI.in tension fractures trending southeast and along a moreOn the positive side, there is now for all intents and purposes, southeasterly trending R shear within a sinistral, strike-slipunlimited computational capability. Full waveform inversions, system whose main displacement zone constitutes the SSE- use of complex number theory for stabilising potential trending, 3 km-wide, Tolukuma-Saki Fault System. LANDSATfield datasets via the Cauchy integration theorem, rigorous imagery suggests that this fault system could extend for someidentification of measurement errors and tracking these 24 km across the Boundary Volcano. through modelling to produce uncertainty estimates, all Detailed study within the mined area indicates a complexcontribute to understanding hidden geology.array of small-scale faults and veins with variable dips, although the strike of many such structures, in particularEvolution of depth estimation techniques by using those of the veins, follows the general trend of the regionalpotential field data.faults and mined veins. This known regional fault geometry enables testing palaeostress inversion analysis as a tool toDesmond FitzGerald, Jeffrey B.Thurston 1 and Ed K. Biegertassist and enhance early-stage mineral exploration. Given the complexity of PNGs tectonic history and the probability1 Intrepid Geophysicsof non-ideal conditions at Tolukuma for use of palaeostressA complete quantitative interpretation of potential field data inversion methods, approximately 18-20 of the 49 slickenlinedaims to estimate three types of information about sources small-scale faults used gave results clearly consistent with theof geological interest: depth, dimensions, and the contrast overall kinematic picture enabled from prior knowledge of theof relevant physical properties. In most applications depth geometry of the mined ore-bodies and faults, with additionalestimates are of great interest.results suggesting the importance of considering the probable effects of an increasing gravitational load during faulting. Historically, different methods have been developed to estimate magnetic depth including Euler deconvolution, Naudy, Source This suggests the utility of palaeostress inversion analysisParameter Imaging- improved (iSPI), and magnetic transects. as a tool during the early stages of exploration for assessingAll these methods have benefits and issues. All methods rely probable extensional fault and vein patterns that could hoston calculated derivatives of the measured magnetic field. As mineralisation, with the reservation that effective use of theMoores law has delivered effectively unlimited computing tool requires time and care when making field observations andcapacity, today more correct methods can be implemented.when core-logging.None of this mathematics is new, being more than 100 years old. Existing approaches cut corners which leads to numerical Interpreting aeromagnetic data in areas of limitedinstability and compromised results. Cauchy derivatives by outcrop, an update from 1997. integration are stabilised and more precise. This stems from exploiting potential field holomorphic properties, which are Desmond FitzGerald and Peter J. Gunn currently ignored. This leads to enhanced noise suppression and In 1997, P.J. Gunn, D. Maidment & P.R. Milligan authoreda more stable version of the `signal` in complex number form.Interpreting aeromagnetic data in areas of limited outcrop. ItThe Cauchy method provides high fidelity edge representation defined a clearly articulated audit of the methods and thinkingand detection and reduced ambiguity.required to infer solid geology. The current paper identifies current improvements in computational geophysics methods,In this paper, the performance of the Pade Approximation in Machine Learning and Artificial Intelligence developmentsconjunction with Cauchy methods will be demonstrated by and provides a score card evaluation of current best practiseusing a range of synthetic models and borehole calibrated against the original papers definitions. The Highland Rocks casereal-life examples. The popular Tikhonov inversion pipeline also FEBRUARY 2023 PREVIEW 96'