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

Morstone Station is situated approximately 50 miles north-east of Camooweal, on the Camooweal 4-mile sheet, North-west Queensland. The owners of the property, Western Grazing Co. Pty. Ltd., have experienced difficulties in obtaining underground water on part of their property for many years, and have asked for this report because the Bureau's 'Camooweal Party' has spent a considerable time during the present field season (1953) completing the mapping of the Camooweal sheet. A number of geologists have contributed to the mapping of the area, notably Dr. F.W. Whitehouse, but the more detailed mapping and investigation are largely the work of Dr. A.A. Opik, Senior Palaeontologist, Bureau of Mineral Resources, who is at present expending the work of previous field seasons. A number of bores were sited for the Company by K.A. Townley, Bureau of Mineral Resources during a short visit in 1951. Three of his proposed sites correspond reasonably closely to our sites A, B and C. Recent investigations, in which the writers have shared, throw some new light on problems of underground water supply on Morstone property, but as the work is still in progress the present report deals only with the specific problems on which the Company's representatives have requested urgent advice.

Introduction Developing predictive numerical models of hydrogeochemical systems requires an understanding of the physical and chemical processes affecting the composition of the water. Physical processes like mixing and evaporation can be reasonably well defined using the chemical data but redox sensitive chemical processes are more difficult to quantify. Applying the isotope chemistry of dissolved sulfate to characterise and even quantify these redox processes enhances the capabilities of numerical modelling, in particular those associated with acid mine drainage, acid sulfate soils and sulfide mineral exploration. This work describes how the stable isotopes of sulfur and oxygen in sulfate can be used to better characterise geochemical processees and thereby improve reactive transport models. Discussion Groundwater, pore water and surface water from a number of areas in Australia have been used to determine the sources of sulfur in acid sulfate susceptable systems. Several trends become apparent, sulfate reduction, and sulfide oxidation commonly dominate the chemical processes controlling sulfur in a groundwater system. Bacterial sulfate reduction (BSR) can be recognised by the affect on the 34S and 18O of sulfate. Both ratios increase as the lighter isotope is removed through dissimilatory bacterial reduction, leaving behind the heavier isotopes. Oxidation of sulfides occurs through 2 processes, one involving molecular oxygen (O2) and the other involving oxidised iron (Fe3+). The different pathways result in considerable differences in the oxygen isotopic composition of the product sulfate. Surface water and some groundwater from the Loveday basin in SA show evidence of evaporation and BSR while the near surface pore waters, although similarly evaporated, contain sulfate that predominantly originates from sulfide oxidation. Sulfate in groundwater from several other regions has stable isotopic compositions that indicate sulfide oxidation involving either the O2 or the Fe3+ pathways. The implications of are that the sulfate history can be understood through isotopic analysis and that this can be used in geochemical models to trace

On 21st November, 1944, a visit was made to the above block at the request of the lessee (Mr. G.D.C. Tanner) who had asked for advice regarding water supply. The report following this visit recommended the testing of an alluvium-filled basin which occupies part of the southeastern quarter of the block. Subsequently Mr. Tanner sank a well at a site about 1,000 feet south of the point indicated as most favourable. For all practical purposes it may be considered that the well has proved that the alluvium is not capable of yielding a useful supply of water at the end of a dry period, and it became necessary to consider the possibility of obtaining water from the bedrock. The present report embodies results of a further examination with this end in view. The location, topography, geology, and possibility of underground water at Block 10 are discussed in this report. A geological sketch map of Block 10 is included.

A visit was paid to Gidleigh Station on Saturday, January 12th. The ten bores previously put down on the property were examined. Details including depth, flow, elevation, and the results of observations made at the site, are given in this report.

A geological examination of the Hog Farm and its vicinity in Gungahlin District was undertaken in response to a request from the Property and Survey Branch, Department of the Interior. The object of the survey was to determine the possibilities of obtaining underground water and to indicate any areas considered favourable. The location, topography, geology, and possibilities of obtaining supplies of underground water at Hog Farm are discussed in this report. A geological plan of the vicinity is included.

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available