A spatial link between granitic intrusions and significant gold deposits has long been recognised in the Pine Creek, Tanami and Tennant Creek areas. However, both locally in these areas, and globally in similar systems, there have been protracted debates as to whether or not the spatially-related granitic intrusions are an essential ingredient in the formation of adjacent gold deposits. None-the-less, it is increasingly being accepted that the granite intrusions do play an important role and a new class of granite-related conceptual exploration models are now emerging. The two best known are Thermal Aureole Gold (TAG, Wall and Taylor, 1990) or Intrusion-Related Gold (IRG, Sillitoe and Thompson, 1998). Key ingredients in the TAG or IRG models are ilmenite- to magnetite-stable granitic intrusions and fluids to transport the metals from these granites to the sites of deposition. The depositional sites are rarely within the intrusion itself, and deposits can occur up to 5 kms from the granite boundary. Wall (in press) noted that this style of deposit is commonly located in the tops and roof zones of plutons, commonly in anticlinorial zones. Globally significant gold deposits that have been assessed as TAG or IRG types include Muruntau (>100 Moz @ 2-3 g/t), Fort Knox (>5.6 Moz), Pogo (5.7 Moz @ 17.8 g/t) Obuasi (>49 Moz) and Campbell-Red Lake (>25 Moz @15 g/t) (Wall, in press; Thompson and Newberry, 2000). It is the aim of this paper to benchmark the district to regional scale parameters of gold mineralisation in the Pine Creek, Tanami and Tennant Creek areas against these conceptual models and note any implications for exploration strategies. This review will consider some other NT provinces, but not the Arunta Province as insufficient details on the granites and sedimentary/ metamorphic sequences are currently available to confidently predict the location of potential IRG or TAG environments.

An outcrop of marmatite (zinc sulphide) has been located within the boundaries of E.P.L.26 held by New Guinea Goldfields Limited. The following notes describe the outcrop as discovered and certain recommendations are made to assist in the evaluation of the outcrop as a base-metal orebody. Other recommendations are made embracing other known occurrences of base-metal sulphides in the Territory of Papua and New Guinea.

Deciphering element associations and affinities in the regolith is important for understanding mineral hosts and geological processes, such as sorting and pedogenesis. This has implications in environmental sciences in terms of distinguishing natural vs. anthropogenic element distributions and establishing realistic remediation targets. In mineral exploration, the strongest elements associations often drive distribution patterns in geochemical maps, yet these are not always the most useful ones to consider. In this contribution, we use National Geochemical Survey of Australia (NGSA) data to (1) identify the strongest controls of mineralogy (using major element total concentrations as a proxy) on trace metal distribution (using aqua regia Cu as an exemplar), and (2) remove the trend driven by the strongest major‒trace element association to calculate and map standardised residuals of the metals. In the coarse fraction (<2 mm) of NGSA top outlet sediments (0‒10 cm depth), which are similar to floodplain sediments, aqua regia Cu is most strongly correlated with total Fe of all the major total elements (r = 0.76 based on log‒transformed concentrations). Thus the aqua regia Cu map mostly shows regions where Fe‒oxyhydroxides in the regolith are abundant (or not) and naturally adsorb dissolved cationic metals from surrounding solutions. The predicted Cu map based purely on the total Fe concentrations and on the Fe‒Cu correlation is visually similar to the raw map. Only when calculating the standardised residuals between actual and predicted aqua regia Cu does additional information become apparent in the form of completely different geochemical patterns. These highlight areas where Cu that is not related to Fe (and therefore not in the form of Cu adsorbed onto Fe‒oxyhydroxides) is abundant (or not). For instance this Cu could be associated with silicate, carbonate or sulfate minerals. Thus this approach allows both environmental management and exploration strategies targeting different types of metal associations to be more effectively implemented, thereby reducing risk and cost. This Abstract & Poster were presented at the 2017 Goldschmidt Conference (https://goldschmidt.info/2017/)

Extensive benefits and tools can be gained for mineral explorers, land-users and government and university researchers using new spectral data and processing techniques. Improved methods were produced as part of a large multi-agency project focusing on the world-class Mt Isa mineral province in Australia. New approaches for ASTER calibration using high-resolution HyMap imagery through to testing for compensation for atmospheric residuals, lichen and other vegetation cover effects have been included in this study. . Specialised data processing software capable of calibrating and processing terabytes of multi-scene imagery and a new approach to delivery of products, were developed to improve non-specialist user interpretation and comparison with other datasets within a GIS. Developments in processing and detailed reporting of methodology, accuracies and applications can make spectral data a more functional and valuable tool for users of remote sensing data. A highly-calibrated approach to data processing, using PIMA ground samples to validate the HyMap, and then calibrating the ASTER data with the HyMap, allows products to have more detailed reliable accuracies and integration with other data, such as geophysical and regolith information in a GIS package, means new assessments and interpretations can be made in mapping and characterising materials at the surface. Previously undiscovered or masked surface expression of underlying materials, such as ore-deposits, can also be identified using these methods. Maps and products made for this project, covering some ~150 ASTER scenes and over 200 HyMap flight-lines, provide a ready-to-use tool that aids explorers in identifying and mapping unconsolidated regolith material and underlying bedrock and alteration mineralogy.

Evaporites comprise all deposits formed by the evaporation of water and the precipitation of its constituents, such as calcium sulphate, sodium chloride, and potassium compounds. They may be found as rock-gypsum, anhydrite, rock-salt or potash-salt deposits at depth in pre-Recent geological series, or as Recent formations of gypsum and salt on the surface. The main object of this report is to show the conditions under which evaporite sediments are formed, what salt deposits are to date known in Australia, where rock-gypsum, rock-salt and potash-salt deposits may be expected within pre-Recent formations, and how further investigations should be carried out.

Iron (Fe) oxide mineralogy in most Australian soils is poorly characterised, even though Fe oxides play an important role in soil function. Fe oxides reflect the conditions of pH, redox potential (Eh), moisture and temperature in the soil environment. The Fe oxide mineralogy exerts a strong control on soil colour. Visible-near infrared (vis-NIR) spectroscopy can be used to identify and measure the abundance of certain Fe oxides in soil as well as soil colour. The aims of this paper are to: (i) measure the hematite and goethite content of Australian soils from their vis-NIR spectra, (ii) compare these results to measurements of soil colour, and (iii) describe the spatial variability of hematite, goethite and soil colour, and map their distribution across Australia. The spectra of 4606 surface soil sample from across Australia were measured using a vis-NIR spectrometer with a wavelength range between 350-2500 nm. We determined the Fe oxide content from characteristic absorptions of hematite (near 880 nm) and goethite (near 920 nm) and derived a normalised iron oxide difference index (NIODI) to better discriminate between them. The NIODI was generalised across Australia with its spatial uncertainty using sequential indicator simulation. We also derived soil RGB colour from the spectra and mapped its distribution and uncertainty across the country using sequential Gaussian simulations. The simulated RGB colour values were made into a composite true colour image and were also converted to Munsell hue, value and chroma. These colour maps were compared to the map of the NIODI and both were used for interpretation of our results. The work presented here was evaluated using existing studies on the distribution of Fe oxides in Australian soils.

Large areas of prospective North and North-East Queensland have been surveyed by airborne hyperspectral sensor, HyMap, and airborne geophysics as part of the 'Smart' exploration initiative by the Geological Survey of Queensland. In particular, 25000 km2 of hyperspectral mineral and compositional map products, at 4.5 m spatial resolution, have been generated and made available via the internet. In addition, more than 130 ASTER scenes were processed and merged to produce broad scale mapping of mineral groups (Thomas et al, 2008). Province-scale, accurate maps of mineral abundances and minerals chemistries were generated for North Queensland as a result of a 2 year project starting in July 2006 which involved CSIRO Exploration and Mining, the Geological Survey of Queensland (GSQ), Geoscience Australia, James Cook University, and Curtin University. Airborne radiometric data acquired over the same North Queensland Mt Isa - Cloncurry areas as the hyperspectral surveys, had been acquired at flight line spacing of 200 metre. Such geophysical radiometric data provides a useful opportunity to compare the mineral mapping potential of both techniques, for a wide range of geological and vegetated environments. In this study, examples are described of soil mapping within the Tick Hill area, and geological / exploration mapping within the Mt Henry and Suicide Ridge prospects of North Queensland.

Identifying and mapping regolith materials at the regional and continental-scale can be facilitated via a new generation of remote sensing methods and standardised geoscience products. The multispectral Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) is the first Earth observation (EO) system to acquire complete coverage of the Australian continent. The Japanese ASTER instrument is housed onboard the USA's Terra satellite, and has 14 spectral bands spanning the visible and near-infrared (VNIR - 500-1,000 nm - 3 bands @ 15 m pixel resolution); shortwave-infrared (SWIR - 1,000-2,500 nm range - 6 bands @ 30 m pixel resolution); and thermal infrared (TIR 8,000-12,000 nm - 90 m pixel resolution) with a 60 km swath. Although ASTER spectral bands do not have sufficient spectral resolution to accurately map the often small diagnostic absorption features of specific mineral species, which can be measured using more expensive 'hyperspectral' systems, current coverage of hyperspectral data is very restricted. The extensive coverage and 30m pixel size of ASTER make it well suited to national scale work. The spectral resolution of ASTER make it best suited to mapping broader 'mineral groups', such as the di-octahedral 'Al-OH' group comprising the mineral sub-groups (and their minerals species) like kaolins (e.g. kaolinite, dickite, halloysite), white micas (e.g. illite, muscovite, paragonite) and smectites (e.g. montmorillonite and beidellite). Extracting mineral group information using ASTER, using specially targeted band combinations, can find previously unmapped outcrop of bedrocks, weathering products, help define soil type and chemistry, and delineate and characterise regolith and landform boundaries over large and remote areas.

A test survey was made with a Radore Equipment over three mineralised areas in Tasmanian. The investigations were made in January, 1955 for the purpose of comparing the performance of the Radore equipment with that of lower-frequency electromagnetic equipment previously used successfully over the same areas. The results show that although some very weak indications were recorded by the Radore equipment, it has not been possible to correlate these satisfactorily with the know mineralisation. Moreover, it is difficult to distinguish indications that may possibly be due to mineralisation from apparent indications that are undoubtedly due to irregularities in topography.

<p>This data package includes raw (Level 0) and reprocessed (Level 1) HyLogging data from 25 wells in the Georgina Basin, onshore Australia. This work was commissioned by Geoscience Australia, and includes an accompanying meta-data report that documents the data processing steps undertaken and a description of the various filters (scalars) used in the processed datasets. <p>Please note: Data can be made available on request to ClientServices@ga.gov.au