b'AEGC 2021Short abstractsnear-surface. AEM can be flown rapidly and cost-effectively overDugald River is a world-class deposit with a resource of 68 large swathes of land providing data with high-lateral resolution.Mt @ 11.6 % Zn and 1.2 % Pb, 26.1 g/t Ag. The deposit has Where AEM bulk conductivity are well correlated with groundwaterexperienced a protracted history of polyphasal folding, salinity in aquifers, AEM can be used to model groundwater salinityshearing, boudinage and brecciation with mineralisation in the data sparse areas between the boreholes. governed by a prominent shear zone. This has caused the orebody to become attenuated, anastomose, pinch and swell We present here a probabilistic method for modelling salinityinto a complex array of ore textures with varying sulphide and case study from the Keep River Plains in the Northerndistribution and alteration occurrence. The deposit is hosted Territory. Co-located probabilistic AEM inversions and ECwithin the Dugald River Slates and consists predominantly measurements on pore fluids at coincident locations were fusedof sphalerite with a variable distribution of galena, Ag and to calculate an empirical joint probability density function.gangue pyrrhotite, pyrite and carbonate. The key ore texture This function allowed us to estimate salinity away from thetypes include banded, transposed ore, milled breccias with bores by sampling the ensemble of AEM conductivities. Unlikemassive sulphide matrix, sulphide bearing carbonate crackle deterministic methods that provide a single estimate of salinity,breccias and lesser low-grade sphalerite to pyrrhotite-pyrite our method generates an ensemble of estimates, which can bestringers. Chalcopyrite occurs in the hangingwall of the used to quantify predictive uncertainty. The results provided byorebody within quartz vein breccia, with pyrrhotite-pyrite our method can feed into decision making while accountingstringers and the brecciated margins of localised albitite. The for uncertainty, enabling remote communities to manage theirCu resource sits at ~10Mt and is discontinuous due to data land and water resources more sustainably. paucity but contains strategic value due to the association with Au, Co and Mo. The Dugald River Slates are enriched 203: 3-D Gravity geometry inversion of the Mathesonin K, Ba and Mn as widespread K-feldspar, hyalophane and Area, Abitibi Greenstone Belt: maintaining the contactsmanganiferous variants of carbonate, garnet and sphalerite. of one of the geological unit fixed for obtainingCarbonate and Fe-sulphides are extensive throughout the slates and are considered paragenetically pre-, syn- and superior results post- mineralisation. The deformation history includes S 1Mr Fabiano Della Justina 1 and Prof Richard Smith1 preserved within altered porphyroblasts, which are aligned parallel to the pervasively developed S 2cleavage, whilst 1 Laurentian University an S 3crenulation cleavage is localised to the hangingwall micaceous schists and mafic porphyry. Past research Gravity Inversion is an important tool for interpreting andpresents conflicting deposit origins from exhalative understanding geological structures in the subsurface. Theformation, to the structural modification of exhalative main goal of an inversion is to perturb a geophysical/geologicalsulphides to a pure epigenetic origin post-dating peak model to accomplish an acceptable level of reproducibility of themetamorphism within the lithologically controlled shear model data with the observed data. There are several inversionzone. The deposit remains open along strike and at depth techniques described in the literature. Some of them are wellwith significant opportunities for growth possible based on established and have been used extensively in the geophysical- current orebody knowledge.data-interpretation workflow; others are still developing. Regardless of which technique is utilized more realistic results are usually achieved when geological constraints are taken into206: Towards standard technical Deeds for (airborne) account. Using measured density values and surface geology asgeophysical surveys in Australiaconstraints, and a compilation of two data sets of ground gravity as observed data, 3D inversions using the VPmg algorithm wasDr Yvette Poudjom Djomani 1 and Dr James Goodwin1used to estimate the subsurface model in the Matheson area,1 Geoscience Australiawhich is located in the southern part of the Abitibi Geenstone Belt, Canada. Besides the aforementioned constraints, theGeoscience Australia (GA) and its predecessors have been contacts of the Porcupine metasedimentary assemblage (oneconducting geophysical surveys since early 50s and processing of the 9 geological units presented in the study area) weredata for many years. GAs role has changed from being a fixed during the inversion. This was because priori 2D forwardpioneer in the acquisition and processing of data to focusing modelling had derived a model also consistent with reflectionon setting standards for the geophysical industry in Australia. seismic data. When the Porcupine assemblage contacts were freeThe experience gained from conducting surveys in the 1990s to move, the thickness was judged to be geologically unrealistic.with modern geophysical equipment is now used to ensure that However, when the Porcupine assemblage contacts were fixed,any government survey is conducted to a level of quality that the model was realistic and there was a smaller misfit betweenensures the collected data is world-class and fit for purpose.predicted and observed data. The geological likelihood of theSince 2003, GA has supervised the processing of several geometries and depths of the geological unit bases obtainedgeophysical surveys collected under contract to the from an inversion, were used as the criteria to judge whether aStates/NT agencies. This degree of exposure to various model was realistic or unrealistic. contractors, survey configurations and environments provides GA with an unprecedented level of insight into 205: Geology of the shear zone hosted Dugald Riverideal processing routines and survey parameters to deliver Zn-Pb-Ag deposit, Mt Isa Inlier, NW QLD quality pre&checkhyphenorendash;competitive products for interpretation.Mr Corey Jago 1, Mr Pieter Creus2 and Mr Shaun Neal1 Deeds of Standing Offer were introduced in 2003. Suppliers 1 MMG Ltd. on the Deed have been pre-approved to provide geophysical 2 James Cook University data , processing and supply services to GA, meaning the 97 PREVIEW AUGUST 2021'