Presentations

A collaborative project between the Geological Survey of New South Wales (GSNSW) and Kenex Pty Ltd was undertaken to evaluate the mineral potential of MGA Zone 54 in NSW as a continuation of GSNSW’s ongoing program of mineral potential mapping across the state, which commenced in the southern New England Orogen in 2017. The results of the Zone 54 project will deliver a pre-competitive geoscience data package that will be used to guide mineral exploration and land-use planning in the region. Prior to modelling, the available datasets were reviewed and updated by GSNSW to ensure accuracy and that relevant attribute information was present. Using a mineral systems approach, models were developed for Broken Hill Type Pb-Zn-Ag and IOCG mineralisation in the Curnamona Province, and Orogenic Au and VHMS mineralisation in the Delamerian-Thomson Orogens. The component processes in the mineral system models were translated into mappable targeting criteria. The key predictive variables, mapped using geological, geochemical, and geophysical datasets, were determined using spatial statistics. Mineral potential maps were generated for each mineral system using a weights of evidence approach. Area-frequency analyses show model efficiencies between 88-99%, which indicate almost all training points used to represent evidence of the mineral system being targeted are predicted within a small area. A comprehensive spatial data table outlining the details of the mappable targeting criteria and the results of the spatial data analysis, and maps of the key predictive variables were delivered, along with the mineral potential maps as a pre-competitive dataset for public release.

The discovery of the Tampia Hill orogenic gold deposit in the wheatbelt of Western Australia has sparked interest in this under-explored region of the state. The deposit is hosted within a granulite facies greenstone belt, with mineralisation mostly hosted in mafic gneiss, which has been intruded by undeformed and unmetamorphosed granite. A lack of outcrop in the project area has meant that geophysics has been vital for interpretation of the geology. A recent gravity and magnetic survey has allowed the most detailed interpretation of the underlying lithology and structures to date, and has highlighted previously unknown areas of mafic gneiss, with a similar signature to that at Tampia Hill. In order to extract the most useful information from the survey, spatial statistical analyses were conducted on the gravity survey data. The analyses over the project area map features within the gravity data that can be used to identify areas of known gold mineralisation. The results confirm that the gravity data not only provides critical geological information, but will also allow the identification of high priority targets for future exploration using spatial data modelling techniques.

Logging of drillholes using wireline tools is an emerging methodology in mineral exploration that adds valuable data to exploration drilling. RC drilling is relatively cheap and quick, but it comes with the price of lost sample integrity and structural coherence. Wireline logging can cover this loss, by facilitating structural interpretations based on borewall imagery. Rock property data can also be recovered below the sampling resolution, such as optical televiewer (OTV) imagery, density, magnetic properties, natural gamma radiation and acoustic properties on cm and even mm scale. In the field, wireline logging will add just a few days to the drilling programme. A team of wireline technicians run their wireline down a recently completed drillhole using an assortment of tools depending on the requests of the client, at a cost amounting to only a few dollars per metre. The tools are oriented with magnetometers and accelerometers, enabling directional logging of geological features the drilling passed through. Combined with on-site logging of lithology and data from tools used in the field, wireline logging will enable exploration to take a significant step towards complete understanding of the prospect geology. In this paper we show downhole logging results from Tampia Hill, Western Australia, and how this work has been used to establish a structural framework and guide the creation of 3D geological and mineral potential models

The Southern New England Orogen (SNEO) in the northeastern part of New South Wales (NSW) is prospective for intrusion-related tin-tungsten, intrusion-related gold-bismuth-molybdenum-silver and orogenic goldantimony mineral systems. An initiative by the Geological Survey of NSW to conduct mineral potential modelling for these mineralisation styles in the SNEO has resulted in a comprehensive account of the mineral resource potential of the region. The Geological Survey of NSW has a successful strategy of providing high quality pre-competitive data that has been complemented and enhanced by the mineral potential mapping approach. Datasets including seamless basement geology, detailed attribution of faults, and igneous fertility that were created by the survey prior to modelling enabled an extensive number of variables be tested for relevance to each mineral system. The feedback from the data processing and spatial analysis allowed improvements to be made to the data and provided information on the relevance of the datasets to mineral exploration in the region. The outputs of the models are mineral potential maps that map the geological potential of the SNEO for each mineralisation style. The models will be used for land planning and advice purposes, technical resources for improved mineral system studies including global endowment estimations, and for promoting exploration in the SNEO through the generation of prospective targets. Due to the richness of the geological datasets in NSW it is likely that the technique, including the creation of high-quality datasets combined with mineral potential modelling, can be successfully applied to other mineralised regions within NSW.

Mineral prospectivity modelling using geographic information systems (GIS) has been used in New Zealand since 2002 both by the government, to promote mineral exploration in New Zealand, and industry, to inform project acquisition and increase the efficiency of exploration programmes. Over the last 15 years at least 38 mineral prospectivity models have been completed in New Zealand covering most of the hard rock mineralised regions onshore as well as nodular phosphate offshore on the Chatham Rise.

Analysis of highly prospective targets generated from the models already completed in New Zealand provides important information about the mineral potential of the country. Onshore, highly prospective targets over a range of commodities cover only 0.5 percent of the total land area of New Zealand, significantly narrowing the search area for new mineral deposits. 83 percent of the targets occur outside public conservation land, and 45 percent of the targets are unpermitted at the time of writing, suggesting there is potential for increased exploration investment and for new discoveries to be made. Prospectivity modelling has had a measureable positive impact on exploration activity and project development in New Zealand over the last 15 years. Future work should include incorporating new data into existing models, modelling new areas when data becomes available, improving existing mineral occurrence datasets, 3D prospectivity modelling, modelling of other commodities such as coal, alluvial gold and ironsand, infrastructure modelling, and exploration effectiveness analysis.