b'AEGC 2023Short abstractsand magnetic datasets, which have proven highly effective forThe Cloncurry mineral system comprises a spectrum of deposit geothermal assessment. Airborne geophysical acquisition isstyles, not observed across the other major IOCG provinces, possible over almost any terrain, with uniform coverage overand provides an excellent window into the array of possible 100% of the area, and with no requirement for ground access. geophysical signatures. This study synthesises findings of HeliFalcon airborne gravity gradiometer (AGG) andCloncurry METAL, a three year study which collected integrated Helitem airborne electromagnetic (AEM) technologies andpetrophysics, mineralogy and structural data from almost every complementary magnetic data (acquired by both systems) havemajor deposit/prospect in the Cloncurry district. It provides been used globally to acquire high-quality multiphysics datasets.petrophysical properties of the host rocks and mineralised We provide a summary of these advanced airborne technologieslithologies across the mineral system. It will explore some and show datasets of high value for geothermal exploration. of the ways variations in host rock chemistry and rheology, structural controls and redox/pH zonation interact to form HeliFalcon AGG is the only high-resolution gravity systemcontrasting geophysical targets. Strategies to deal with difficult operable from helicopters and provides high quality gravityaspects of geophysical interpretation of IOCG targets, including data over virtually all terrain, at resolutions to 50 m andjoint modelling of magnetic and gravity data, incorporating lower. Data is ideal for detailed structural architecture mapping,remanence and self-demagnetisation effects into modelling and litho-structural mapping of tectonic, volcanic and igneousprocedures, and mapping structural controls will also be features (faults, lava domes, lava flows, intrusives, calderas,explored, citing specific examples from the Cloncurry district.basins, sub-basins), and general geology.Helitem AEM operation at frequencies as low as 6.25 Hz, hasPassive seismic methods for obtaining shear-wave enhanced depth of exploration and greater sensitivity to targetsvelocity profiles and depth to basement in an urban-at all depths. Helitem AEM data maps subsurface resistivityindustrial area, Marmara region, Turkey.distribution in 2D and 3D, aquifers, lithological distribution, and particularly low-resistivity clay-caps related to hydrothermalMichael Asten, Abdullah Altndal1, Aysegul Askan1, alteration. Resistivity depth slices and 3D iso-surfaces map lowFatmaNurten Sisman1, Shaghayegh Karimzadeh Naghshineh2, resistivity zones, giving information on fluid sources, pathways,Serif Baris3 and Deniz Caka3conduits at fault intersections, and alteration.1 Middle East Technical University, Civil Eng. Dept., Ankara, Turkey. Complementary magnetic data can also map magnetite2 University of Minho, ISISE, Department of Civil Engineering, destruction due to thermal or hydrothermal alteration. Guimares, Portugal Case histories from Japan and USA, will be used to demonstrate3 Kocaeli University, Geophysical Eng. Dept., Kocaeli, Turkeyhow the acquisition, processing and integrated interpretation ofThe Kocaeli region is located in the eastern Marmara region high-resolution airborne gravity, electromagnetic and magneticof Turkey, near the North Anatolian fault zone. As part of a datasets, along with other available information, is providingprogramme to assess seismic hazard in this earthquake-prone significant benefit to geothermal assessment programmes in aarea, a series of passive seismic (microtremor) studies were made variety of settings. with the objective of acquiring shear-wave velocity (Vs) profiles of the upper few hundred meters of soft and weakly consolidated Geophysical synthesis of Iron-Oxide Copper Goldsediments, over a 5x5 km area. A set of 14 sites were studied using nested triangular passive seismic arrays. Combined use of mineralisation: The influence of protolith, rheology,spatially averaged coherency (SPAC) methods and horizontal/structural control and redox. vertical particle motion ratios was successful in documenting James Austin thickness and Vs variations over depth ranges from 2 m to 500 m. Particular challenges addressed in this survey were in the CSIRO processing of data from an environment with highly variable local Iron oxide copper-gold (IOCG) systems form in a range ofseismic noise sources in this urban and industrial setting.lithologies, including variably metamorphosed felsic and maficApart from successful definition of softness of sediments in the volcanics, carbonates and siliciclastic sedimentary rocks. Theupper 100 m, the survey resolved seismic basement (Vs ~1200 chemistry, porosity and permeability of the host rocks controlm/s) at depths ranging from 160 m in the north to 500 m in the reactive potential of mineralising fluids. They form acrossthe south-west. While the number of sites is limited there is an a range of crustal rheologies, from mid-crustal (ductile) toindication that the trend of deep basement estimates is in a upper-crustal (brittle) conditions. IOCGs are focussed via anorth-easterly direction which corresponds with the direction of range of structural controls, including permeable strata, shearexpected secondary tensional faulting associated with the primary zones, fault jogs, splays and intersections and breccia pipes. Thedextral east-west shear faults of the North Anatolian fault zone.mechanism of fluid localisation controls geophysical zonation (e.g., planar vs concentric zonation). IOCGs also comprise a spectrum of mineralisation assemblages from reduced,MagResource: An environmentally conscious, pyrrhotite-dominant examples, to magnetite-dominant, andgeophysical approach to resource definition.more oxidised, hematite dominant deposits. These Fe-bearing minerals have contrasting magnetic properties, densityJames Austin, Clive Foss and Andreas Bjorkand conductivity and therefore redox/pH and geophysicalCSIRO properties are linked. The interaction of these major controls, host rock chemistry and rheology, structural control, redox/pHMagnetite has characteristic density and magnetic properties, conditions, define the style of geophysical anomaly associatedwhich contrast strongly with most common minerals and with an IOCG system. rock types. Provided magnetite grains within a resource have FEBRUARY 2023 PREVIEW 80'