Short article describing detection of interpreted unconformity between Coolbro Sandstone and Rudall Complex rocks near the Kintyre uranium deposit, Western Australia

A test site for airborne gravity (AG) systems has been established at Kauring, approximately 100 km east of Perth, Western Australia. The site was chosen using a range of criteria that included being within 200 km of Jandakot Airport in Perth where most of the airborne systems would be based at one time or another when operating in Australia, being free of low level flight restrictions, having minimal human infrastructure in the central 20 by 20 km area, and the presence of gentle to rolling terrain rather than deeply incised topography or an extensive flat plain with very low relief. In anticipation of catering for airborne gravity gradiometer (AGG) systems, the site was required to have a gravity gradient feature with clear response in the wavelength range of 100 m to 2 km in a 5 by 5 km core region. In addition to catering for AGG systems, the site may also be used in the future to demonstrate and compare various airborne magnetic systems (TMI, vector, and gradient tensor systems) and digital terrain mapping systems.

Airborne Electromagnetic data are being acquired by Geoscience Australia in areas considered to have potential for uranium or thorium mineralisation under the Australian Government's Onshore Energy Security Program (OESP). The surveys have been managed and interpreted by Geoscience Australia's Airborne Electromagnetic Acquisition and Interpretation project. Three survey areas were recognised in the Pine Creek AEM survey area: Woolner Granite (TEMPEST), Rum Jungle (TEMPEST) and Kombolgie (VTEM). Industry paid for infill - all of this data has now been released to the public domain and is available at the GA website. In contrast to industry style deposit scale investigations, these surveys are designed to reveal new geological information at regional scale. The Pine Creek airborne electromagnetic data were acquired at line spacing's of between one and five kilometres, a total of 29 000 line km and covers an area of 73 000 km squared. The outcomes of the Pine Creek AEM survey include mapping of subsurface geological features that are associated with unconformity-related, sandstone-hosted and palaeovalley-hosted uranium mineralisation. The data are also capable of interpretation for other commodities including metals and potable water as well as for landscape evolution studies. The improved understanding of the regional geology resulting from the Pine Creek survey results will be of considerable benefit to mining and mineral exploration companies. This Data Package is for Archive to the internal area of the CDS and contains all data, grids, images, mxd, shape files, documentation, licenses, agreements, interpretations and scripts used to create the Pine Creek deliverables. At the projects completion (2012) all directories are required to be moved off the NAS. The reason to keep all the files is that more work is to be done on this data in the 2012-2015 period and these files may be needed in this future work.

At present calcrete-hosted uranium deposits constitute only 1% of Australia's uranium resources. Most known deposits (nine out of eleven) are associated with Cenozoic drainage systems in the Yilgarn Craton, and similar drainage systems in the Gascoyne Province and Ngalia Basin. In the Paterson region calcrete-hosted uranium mineralisation has been reported only in the Lake Waukarlycarly area but no major deposit of this type has yet been found.

The Frome airborne electromagnetic (AEM) survey was designed to provide reliable pre-competitive AEM data to aid the search for energy and mineral resources around the Lake Frome region of South Australia. Flown in 2010, a total of 32,317 line kilometres of high quality airborne geophysical data were collected over an area of 95,450 km2 at a flight line spacing mostly of 2.5 km, opening to 5 km spaced lines in the Marree-Strzelecki Desert area to the north. The Lake Frome region hosts a large number of sandstone-hosted uranium deposits with known resources of ~60,000 tonnes of U3O8 including the working In Situ Recovery (ISR) operations at Beverley, Pepegoona, Pannikin and Honeymoon, and deposits at Four Mile East, Four Mile West, Yagdlin, Goulds Dam, Oban and Junction Dam. The aims of the Frome AEM Survey were to map critical elements of sandstone-hosted uranium mineral systems including basin architecture, palaeovalley morphology, sedimentary facies changes, hydrological connections between uranium sources and uranium sinks and structures that may control uranium mineralisation. Interpretations of the data show the utility of regional AEM surveying for mapping sandstone-hosted uranium mineral systems as well as for mapping geological surfaces and depth of cover over a wide area. Data from the Frome AEM Survey allow mineral explorers to put their own high-resolution AEM surveys into a regional context. Survey data were used to map a range of geological features that are associated with, or control the location of, sandstone-hosted uranium mineral systems and have been used to map and assess the prospectivity of new areas to the north of the Flinders Ranges.

During 2008 and 2009, and under the Australian Government's Onshore Energy Security Initiative, Geoscience Australia acquired airborne electromagnetic (AEM) data over the Pine Creek Orogen of the Northern Territory. The survey area was split into three areas for acquisition. VTEM data was acquired in the Kombolgie area east of Kakadu National Park between August and November 2008. TEMPEST data was acquired west of Kakadu National Park with the area split in two to facilitate the use of two aircraft: the Woolner Granite area in the north (this data set) was acquired between October and December 2008; and the Rum Jungle area adjoining to the south, was acquired between October 2008 and May 2009. The main purpose of the surveys was to provide additional geophysical/geological context for unconformity style uranium mineral systems and thereby promote related exploration. The survey data will also provide information on depth to Proterozoic/Archean basement, which is of general interest to explorers, and will be used as an input into ground water studues in the region.

The inversion analyses presented in our paper and now extended in this Reply were ultimately only one part of the AEM system selection process for the BHMAR project. Both Derivative and Inversion analyses are in their nature theoretical, and it is impossible, in a theoretical analysis, to capture all of the aspects relevant for real surveys with little margin for error in political time frames. In reality, neither the Derivative nor Inversion analysis provided the degree of certainty required (by the project manager and client) to ascertain whether any of the candidate AEM systems were able to map the key managed aquifer recharge targets recognized in the study area. Consequently, a decision was made to acquire data over a test line with the 2 systems (SkyTEM and TEMPEST) that performed best in the Derivative and Inversion analysis studies. This approach was vindicated with quite distinctive and very different performance observed between these two systems, especially when compared with borehole and ground geophysical and hydrogeological data over known targets. Data were inverted both with contractors' software and with reference software common to all systems and the results were compared. Ultimately, it was the test line, particularly in the near-surface (top 20metres), thatmade the SkyTEM system stand out as the best system for the particular targets in the project area. SkyTEM mapped the key multi-layered hydrostratigraphy and water quality variability in the key aquifer that defined the key MAR targets, although the TEMPEST system had a superior performance at depths exceeding 100metres. Importantly, the SkyTEM system also mapped numerous, subtle fault-offsets in the shallow near-surface. These structures were critical to mapping recharge and inter-aquifer leakage pathways. Further analysis has demonstrated that selection of the most appropriate AEM system and inversion can result in order of magnitude differences in estimates of potential groundwater resources. The acquisition of SkyTEM data was an outstanding success, demonstrating the capability of AEM systems to provide high-resolution data for the rapid mapping and assessment of groundwater and strategic aquifer storages in Australia's complex and highly salinized floodplain environments. The SkyTEM data were used successfully to identify 14 major new groundwater targets and multiple MAR targets, and these have been validated by an extensive drilling program (Lawrie et al., 2012a-e). Increasingly, the demand from clients for higher certainty in project decision making, and quantifying errors, will see development of new system comparative analysis approaches such as the Inversion analysis approach documented in our initial paper. Ultimately, system fly-offs are likely in high-profile projects where budgets permit.

Extended abstract regarding the Frome AEM data set and Murray Basin geology and landscape evolution

Phase-1 data, that is, contractor quality-controlled and quality-assessed data for Kombolgie, were released during 2009. New EMFlow data, that is data generated using a new EMFlow version are included in this data release. The data and products described in this report are contained on the accompanying DVD. The main products included in this data package include: sections, conductance grids and an AEM Depth of Investigation grid. The data is provided in formats which can be viewed on most computer systems. They include, JPEG (.jpg) with associated world files for easy use in geographic information system (GIS) packages, ER Mapper grids (.ers), ESRI shape files (.shp) of the flight path, and point-located ASCII data with relevant metadata for derived products. The outcomes of the Pine Creek AEM Kombolgie survey include mapping of subsurface geological features that are associated with unconformity-related, sandstone-hosted Westmoreland-type and Vein-type uranium mineralisation. The data are also capable of interpretation for other commodities including metals and potable water as well as for landscape evolution studies. The improved understanding of the regional geology to greater than 1500m resulting from the enhanced EMFlow survey results will be of considerable benefit to mining and mineral exploration companies.

The Ord is one of the largest rivers in northern Australia and is located in the Kimberley region of Western Australia. In this study we show that the lower Ord landscape near Kununurra in Western Australia consists of a large scale ancient landscape, possibly pre-Cambrian, being exhumed from beneath flat-lying Cambrian to Carboniferous cover rocks. Additional post-Permian landscapes are being formed by this process. The Ord Valley alluvium is of late Pleistocene to Holocene in age and consts off upward fining gravels, sands and clays infilling an inset valley profile. The Ord River initially flowed to the sea via the keep River estuary, however a major avulsion, possibly due to sedimentatain topping a low point in the surrounding valley walls, occurred possibly as recently as 1,800 years ago. As a result to mouth of the Ord shifted some 100 km to the east, to Cambridge Gulf, its course through the former alluvial plain and along the new course across the coastal plain was incised, and a scabland formed across the low point of Tararar Bar. This association of very ancient (pre-Paleozoic) landscape elements and by thin, very young weathering profiles and young sedimentary accumulations in alluvial valleys is paradoxical in the broader Australian pattern where very ancient landscape elements are associated with ancient sedimentary infill and weathering profiles.