In 2011, Geoscience Australia collected 484 km of deep-crustal (22 second) seismic reflection data. The survey (11GA-YO1) traverses the north-eastern edge of the Yilgarn Craton, the Officer Basin and the western end of the Musgrave Province. The purpose of the seismic survey was to delineate broad crustal architecture and define the Moho, with particular interest in the Yilgarn-Musgrave boundary. To compliment the seismic survey, a 3D geological model was constructed that incorporates interpretations derived from seismic, potential field, surface geology and borehole data. Forward and inverse modelling techniques were applied to the potential field data to extrapolate the seismic interpretations into 3D space. Borehole data was used to constrain the interpretation of upper crustal sequences where available. The model was later used to constrain 3D potential field inversions of the area. This poster presents a 3D geological model of the YOM region as well as the geological and geophysical constraints that were used to construct it. Some of the fundamental and technical limitations of the model are also discussed.

Poster prepared for International Association of Hydrogeologists Congress 2013 Sonic drilling is a relatively new technology that was used successfully to obtain relatively uncontaminated and undisturbed continuous core samples with excellent (>99%) recovery rates to depths of 206m in unconsolidated fluvio-lacustrine sediments of the Darling River floodplain. However, there are limitations with the standard sonic coring method. Sands, in particular, are disturbed when they are vibrated out of the core barrel into the flexible plastic sampling tube. There can be changes to moisture content, pore fluid chemistry and sediment mineralogy on exposure to the atmosphere, even when the samples are processed and analysed soon after collection. The option exists during sonic drilling to encapsulate the core in rigid polycarbonate lexan tubes. Although this increases costs and reduces drilling rates, atmospheric exposure of the core during drilling is reduced to the ends of the lexan tubes before being capped. In addition, the tubes can be purged with an inert gas such as argon. Lexan coring is best carried out below the watertable as the heat from drilling dry clays can cause the polycarbonate to melt. In the study, 60 sonic holes (4.5 km) and 40 rotary mud holes (2 km) were obtained as part of a program to map and assess potential groundwater resources and managed aquifer recharge (MAR) targets over a large area (7,500 km2) of the Darling River floodplain. Two of the sonic bores were drilled to depths of 60 metres to obtain lexan-encapsulated core samples. These cores were used to obtain less perturbed samples for pore fluid analysis (salinity, major ions, trace metals, stable isotopes), textural analysis, and analysis of mineral phases to help assess aquifer clogging potential (using XRD, XRF, SEM). An additional advantage of the lexan coring was the recovery of encapsulated and intact sediment intervals for determining porosities, effective porosities, hydraulic conductivities, and other geophysical and petrophysical measurements. By painting some tubes black, sand samples were also successfully obtained for optically stimulated luminescence (OSL) dating. Alternatively, opaque black lexan can be made to order by the supplier. Overall, the superior sample integrity obtained from lexan coring enables a greater range of hydrogeological and hydrochemical parameters to be assessed.

As part of the National CO2 Infrastructure Plan, Geoscience Australia is undertaking a three year project to provide a detailed assessment of the Vlaming Sub-basin prospectivity for the geological storage of CO2. An important part of this assessment is an evaluation of the seal quality and integrity, including analysis of fault reactivation, signs of seepage, as well as lithological variability within the seal. Over a large area the Gage reservoir is underlain by the Charlotte reservoir (Figure 1). Based on well data, the two reservoirs are at least partially connected. Due to limited data, the Charlotte reservoir was not considered by the previous studies for additional storage capacity. Even if Charlotte Sandstone is not considered for storage, it presents a base seal issue for CO2 storage in the Gage reservoir, which needs to be addressed. The current study mapped the Charlotte reservoir and analysed its potential impact on the containment of CO2. Initial results of this study are outlined below.

Geoscience Australia has committed to an integrated program of data stewardship with the inception of the Geoinformatics and Data Services Section (GDSS) in 2013, whose mission is to maximise the online discovery, access, sharing, interoperability and use of Geoscience Australia's science data. The section comprises small teams of specialists whose skills cross the realm of geoscience, computer science, spatial science, policy, information management and IT. These teams research, strategise, plan, coordinate, advise, innovate, implement and manage enterprise data, systems, tools and services with a unique awareness of the interdependencies between IT, science, culture and governance. GDSS collaborates with researchers and experts to ensure the projects, standards, models and tools we implement are international best practice. This poster highlights some of the initiatives we are progressing.

Homogeneity Tests for a Rotary Sample Divider Two rock types, a coarse-grained granite and a finer-grained volcanic rock, were used to test a Rotary Sample Divider attached to a Rocklabs Boyd Crusher for homogeneity. Approximately 3kg of each rock type were broken down by a jaw crusher, and then processed through a Boyd Crusher with splits taken using the attached rotary sample divider. The formula 10/(100-(10*n))-where n=the number of the split-was used to process the entire sample, i.e., 10% of the first split was taken and remainder returned to the Boyd crusher; 11% of the second split taken and remainder returned to the crusher; 12.5% of the 3rd one taken and remainder returned to the Boyd crusher etc., until all the sample was used and there were 10 roughly equal splits. Each split was halved and each half pulverised for 3 minutes in a Tungsten Carbide ring mill for 3 minutes. Pressed powder pellets and Lithium Borate glasses were made and analysed using a PW2404 XRF spectrometer. Results of major and trace element analysis shows that there is no apparent bias between either individual splits or from the first split to the last split, indicating homogeneity was achieved using the rotary sample divider.

The National Geochemical Survey of Australia (NGSA; www.gov.au/ngsa) collected and analysed catchment outlet sediments at 1315 sites over most of Australia (Caritat & Cooper, 2011). Multivariate statistical assessment of the NGSA data revealed significant regional-scale geological features that were supported by independent proximal and remotely sensed geoscientific datasets (Caritat & Grunsky, 2013). The aim of this study was to test, using the NGSA data, whether treating the data according to rigorous Compositional Data (CoDa) principles improved the outcomes of prospectivity analysis for mineral exploration or not.

Poster for temporary display at Ocean Optics Conference Glasgow 2012

Exhibition/Conference display consisting of 3 new panels (will also be used at Open Day). Panels content includes: water observations from space image and introductory text to this mapping.capability.

The Frome airborne electromagnetic (AEM) survey (Figure 1) is the largest of three regional AEM surveys flown under the 5-year Onshore Energy Security Program (OESP) by Geoscience Australia, and the largest survey by area ever flown in Australia. The aim of the survey is to reduce risk and stimulate exploration investment for uranium by providing reliable pre-competitive data. The Frome AEM survey was released with two different Geoscience Australia layered earth inversions (GA-LEI): a sample-by-sample inversion (SBS GA-LEI) to enhance vertical features; and, a line-by-line inversion (LBL GA-LEI) to enhance horizontal features (see Hutchinson et al. 2010). A separate depth of investigation was calculated for each inversion using a method modified after Christiansen and Auken (2010) for the SBS inversion and Oldenburg and Li (1999) for the LBL inversion. A range of data products were produced including point-located ASCII data, georeferenced conductivity sections and grids, PDF multiplots, GOCAD surfaces and ancillary data. A range of under-cover features are mapped in the conductance image (Figure 1), including (but not limited to): extensions to known palaeovalley networks in the Frome Embayment; the under-cover extent of the Benagerie Ridge; regional faults in the Frome Embayment and Murray Basin; folded and faulted Neoproterozoic rocks in the Adelaide Fold Belt; Cenozoic - Mesozoic stratigraphy in the Frome Embayment; neotectonic offsets in the Lake Eyre Basin; conductive Neoproterozoic rocks associated with copper-gold mineralisation; and, coal-bearing structures in the Leigh Creek area, as well as groundwater features. A depth of investigation (DOI - depth of reliable signal penetration) of up to 400 m is calculated in areas of thin cover and resistive basement, e.g., Adelaidean rocks in the Olary Ranges (Figure 2). In Cenozoic - Mesozoic sediments in the Frome Embayment and the Murray Basin the DOI is about 100-150 m, decreasing to less than 50 m under the salt lakes. The Frome AEM data set is available for free download from Geoscience Australia: http://www.ga.gov.au/minerals/projects/current-projects/airborne-electromagnetics.html For more information contact: Dr Ian Roach Continental Geophysics, Geoscience Australia Ian.Roach@ga.gov.au

Poster abstract submission for the AGU2013 Meeting