Groundwater geochemistry, hydrogeology and potash mineral potential of the Lake Woods region, Northern Territory, Australia

We collected 38 groundwater and two surface water samples in the semi-arid Lake Woods region of the Northern Territory to better understand the hydrogeochemistry of this system, which straddles the Wiso, Tennant Creek and Georgina geological regions. Lake Woods is presently a losing waterbody feeding the underlying groundwater system. The main aquifers comprise mainly carbonate (limestone and dolostone), siliciclastic (sandstone and siltstone) and evaporitic units. The water composition was determined in terms of bulk properties (pH, electrical conductivity, temperature, dissolved oxygen, redox potential), 40 major, minor and trace elements as well as six isotopes (δ18Owater, δ2Hwater, δ13CDIC, δ34SSO4=, δ18OSO4=, 87Sr/86Sr). The groundwater is recharged through infiltration in the catchment from monsoonal rainfall (annual average rainfall ~600 mm) and runoff. It evolves geochemically mainly through evapotranspiration and water–mineral interaction (dissolution of carbonates, silicates, and to a lesser extent sulfates). The two surface waters (one from the main creek feeding the lake, the other from the lake itself) are extraordinarily enriched in 18O and 2H isotopes (δ18O of +10.9 and +16.4 ‰ VSMOW, and δ2H of +41 and +93 ‰ VSMOW, respectively), which is interpreted to reflect evaporation during the dry season (annual average evaporation ~3000 mm) under low humidity conditions (annual average relative humidity ~40 %). This interpretation is supported by modelling results. The potassium (K) relative enrichment (K/Cl mass ratio over 50 times that of sea water) is similar to that observed in salt-lake systems worldwide that are prospective for potash resources. Potassium enrichment is believed to derive partly from dust during atmospheric transport/deposition, but mostly from weathering of K-silicates in the aquifer materials (and possibly underlying formations). Further studies of Australian salt-lake systems are required to reach evidence-based conclusions on their mineral potential for potash, lithium, boron and other low-temperature mineral system commodities such as uranium. <b>Citation:</b> P. de Caritat, E. N. Bastrakov, S. Jaireth, P. M. English, J. D. A. Clarke, T. P. Mernagh, A. S. Wygralak, H. E. Dulfer & J. Trafford (2019) Groundwater geochemistry, hydrogeology and potash mineral potential of the Lake Woods region, Northern Territory, Australia, <i>Australian Journal of Earth Sciences</i>, 66:3, 411-430, DOI: 10.1080/08120099.2018.1543208

Geochemical mapping applications to forensics and intelligence

Geochemical surveys deliver fundamental data, information and knowledge about the concentration and spatial distribution of chemical elements, isotopes and compounds in the natural environment. Typically near-surface sampling media, such as soil, sediment, outcropping rocks and stream or groundwater, are used. The application of such datasets to fields such as mineral exploration, environmental management, and geomedicine has been widely documented. In this presentation I reflect on a sabbatical experience with the Australian Federal Police (AFP) in 2017-2018 that allowed me to extend the interpretation of geochemical survey data beyond these established applications. In particular, with my collaborators we explore ways in which geochemical survey data and maps can be used to indicate the provenance of an evidentiary sample collected at a crime scene or obtained for instance from items belonging to a suspect intercepted at border entry. Because soils are extremely diverse mineralogically, geochemically and biologically, it should theoretically be possible to exclude very large swathes of territory (>90%) from further provenancing investigation using soil data. In a collaboration between Geoscience Australia (GA), the AFP and the University of Canberra (UC), a recent geochemical survey of the urban/suburban Canberra region in southeastern Australia is being used as a testbed for developing different approaches to forensic applications of geochemical surveys. A predictive soil provenancing method at the national scale was also developed and tested for application where no actual detailed, fit-for-purpose geochemical survey data exist. Over the next few years, GA, AFP and UC are collaborating with Flinders University to add biome data from soil and soil-derived dust to further improve the provenancing technique. This Abstract was presented at the 2021 Goldschmidt Conference (https://conf.goldschmidt.info/goldschmidt/2021/meetingapp.cgi)

Galilee Basin region: Hydrogen potential package

The potential for hydrogen production in the Galilee Basin region is assessed to provide a joint information base for hydrogen generation potential from renewable energy, groundwater and natural gas coupled with carbon capture and storage (CCS). Hydrogen generation requires water, whether using electrolysis with renewable energy or steam methane reforming (SMR) of gas with CCS. The data package includes the regional renewable energy capacity factor, aquifers and their properties (potential yield, salinity, and reserves or storativity), natural gas resources, and geological storage potential of carbon dioxide (CO2). This data guide gives examples of how the compiled data can be used. The renewable hydrogen potential is assessed based on renewable energy capacity factor and groundwater information (potential yield, salinity, and reserves or storativity). Nine aquifers from the Galilee and overlying Eromanga and the Lake Eyre basins are included in the assessment. The Galilee Basin region has low renewable hydrogen potential except for small areas in the north, south and south-west. Although the renewable energy capacity factor in the basin is high, aquifers tend to have poor groundwater reserves or storativity, which results in lower overall renewable hydrogen potential. The Galilee Basin contains modest contingent gas resources, while sizeable gas reserves and contingent resources were identified in the overlying Eromanga Basin (Geoscience Australia, 2022). The geological CO2 storage assessment suggests that the Betts Creek - Rewan Play interval is the most prospective for CCS, with the highest potential around the central basin region. Further work on identifying detailed gas potential is needed to assess hydrogen generation potential from gas.

Conodont biostratigraphy of the Upper Devonian reef complexes of the Canning Basin, Western Australia

Conodont Biostratigraphy of the upper Devonian reef complexes of the Canning Basin, Western Australia

Application of electronics to offshore oil exploration