Report on the activities of the administrative and technical sections in the Katherine-Darwin area, to March, 1954. A brief account is given of geological and geophysical operations. The results of prospecting and field work are summarised.

This report deals with the results of 22,355 ft. of scout boring over an area of approximately 50 square miles on the western flank of the Muswellbrook (N.S.W.) Anticline. A traverse of overlapping bore-holes, located between the outcrops of the Upper Marine Series (Mulbring Beds) in the east and of the Triassic sediments in the west; provided a more complete section of the Upper Coal Measures in this area than has been previously available. Some 46 coal seams were encountered and tentatively numbered for correlation. Some of the coal seams exhibit very good qualities, but none could be classed as a good gas or coking coal. Igneous intrusions are numerous and of a fairly wide vertical and areal extent; their influence on the associated coal seams is generally destructive. The results of the above boring may be regarded as a basis, for any detailed future underground and/or open-cut mining investigations. No attempt was made to estimate coal reserves of any kind.

A geophysical survey, comprising self-potential and electromagnetic methods, was made during the 1952 and 1953 field seasons at the Labour Victory Copper Mine, about 7 miles north-north-west of the Mt. Elliott Copper Mine, near Selwyn, Northern Queensland. The self-potential survey covered an area of 2,400 feet x 900 feet, but owing to other operational commitments during the 1953 season, the electromagnetic survey was confined to the southern part of the area. The primary object of the work was to determine the extent of the mineralisation associated with the known lode, which strikes north-south through the centre of the surveyed area. The self-potential survey revealed a well-defined anomaly nearly 1,000 feet long, in the northern part of the area. The axis of this anomaly is parallel to, but about 75 feet west of, the known lode. The disused main shaft of the now idle mine is at the southern end of the anomaly, which in this vicinity deviates slightly towards the south-east, i.e. towards the known lode. No workings exist in the area of the indication, and no outcrops were found, the rock formations being hidden for the most part by alluvium. The electromagnetic results confirmed those of the self-potential survey, but the electromagnetic indication extends farther to the south. The results suggest that the indication may be caused by lenticular bodies and that these are disturbed by cross faults. No mineralised deposits were indicated by the electrical results in the southern part of the area. It is recommended that some trenching and geological and geochemical work be done in the area of the strong electrical indication. If the results of the testing show that the indication is not due to graphitic or pyritic schists, it is recommended that a number of diamond drill holes be put down. Suggested locations for five such drill holes are given. If the anomaly is due to ore the geophysical results suggest an ore body of considerable size.

Sediments of the Brock's Creek Group and of the Phillips Creek Formation, and volcanics of the Edith River Formation were prospected with carborne radiometric equipment. A comparatively high background count was recorded in the Edith River Volcanics, but no significant radiometric anomaly was found. A geological party prospected ten shear zones south east of the Edith Siding, including a cupriferous one, and a strongly fractured belt near the granite contact. No radiometric anomaly was found. Future prospecting should be directed towards major faults within the sediments.

This prospect was discovered by Geologist A.B. Clark on the 3rd September, 1953 at a point 11 miles distant and on a bearing of 33 degrees from the Katherine Post Office. Following its discovery a reservation was taken out on behalf of the Bureau of Mineral Resources to protect the area. Detailed geological and geophysical investigations have since been undertaken in the area, and costeaning by hand labour and bulldozer has also been done. The examination and testing of the prospect is not yet complete but a summary of the information concerning the prospect available at 31st October 1953 is given below.

Report on the activities of the administrative and technical sections in the Katherine-Darwin area, to June, 1954. A brief account is given of geological and geophysical operations. The results of prospecting and development work are summarised.

The paper discusses the results from the GA-302 2D seismic survey and GA-2436 (RV Tangaroa) marine reconnaissance survey over the Capel and Faust basins, northern Tasman Sea. The integration of seismic, potential field and bathymetric data sets in 3D space at an early stage in the project workflow has assisted in the visualisation of the basin architecture, the interpolation of data between the seismic lines, and the iterative refinement of interpretations. The data sets confirm the presence of multiple depocentres, as previously interpreted from satellite gravity data, with a maximum sediment thickness of 5-7 km. Preliminary interpretation of the seismic data has identified two predominantly Cretaceous syn-rift and two Upper Cretaceous to Neogene sag megasequences overlying a heterogeneous pre-rift basement. The comparison of seismic facies and tectonostratigraphic history with offshore New Zealand and eastern Australian basins suggests the presence of possible Jurassic to Upper Cretaceous coaly and lacustrine source rocks in the pre- and syn-rift, and fluvio-deltaic to shallow marine reservoir rocks in the syn-rift to early post-rift successions. Preliminary 1D basin modelling suggests that the deeper depocentres of the Capel and Faust basins are within the oil and gas windows. Large potential stratigraphic and structural traps are also present.

Abstract for initial submission; see Geocat 71429 for conference paper version

Uranium-rich igneous rocks are recognised as an important source of metals in uranium mineral systems. Magmatic-related uranium mineralisation may be orthomagmatic in origin, forming via favourable igneous processes, or may result from the exsolution of uranium-rich fluids from particular magmas. Additionally, it is recognised that igneous rocks also may contribute directly to basin-related uranium mineral systems as a metal source. Thus, mapping of the distribution of uranium in igneous rocks has the potential to highlight prospective regions for uranium mineralisation at a macro-scale. Geoscience Australia has produced a series of three digital maps showing the uranium content of igneous rocks across Australia, drawing together geochemical and geological datasets from disparate open file sources. Map 1 shows the uranium concentration in whole rock geochemical analyses plotted as point data on a background of igneous rock type, which itself is derived from Geoscience Australia's 1:1 000 000 national surface geology map. Map 2 integrates these datasets, and shows the average uranium content of all intersecting geochemical data point for outcropping individual igneous rock units. In Map 3, a similar approach is employed in mapping the average uranium content of igneous rocks occurring under cover, using interpreted solid geology coverages. Combined, these maps provide a comprehensive picture of the province-scale trends in igneous uranium content across the continent. Using an applied knowledge of processes leading to uranium concentration in magmatic systems, igneous rocks exhibiting a favourable combination of factors are able to be identified for further analysis of prospectivity for uranium mineral systems.

As part of Geoscience Australia's Onshore Energy Security Program the authors have investigated whether there is any evidence that a sandstone hosted uranium system has operated in the Eromanga Basin and assessed the basin's potential to host significant uranium mineralisation. The Eromanga Basin is a Mesozoic, intracratonic, sag basin that covers ~1,000,000 km2 of central-eastern Australia and it onlaps several surrounding Proterozoic provinces that have elevated uranium contents. The Eromanga Basin has been subdivided into three major stratigraphic sequences: a lower non-marine sequence, a middle marine sequence and an upper non-marine sequence. Each sequence is characterised by basal sands that fine upwards into shales and silts, suggesting a gradual change from high- to low-energy sedimentary environments. The overall structural trend of the basin is oriented north-east, with a series of north-east striking troughs and ridges that locally controlled sediment deposition. Subsequent folding has produced broad, regional domes. To assess the uranium potential in the Eromanga Basin, the pmd*CRC five-questions framework was adopted. This framework attempts to understand the whole mineralising system by addressing (1) the geodynamic and pressure temperature histories; (2) the architecture of the system; (3) the fluid reservoirs; (4) the fluid flow drivers and pathways; and (5) the metal transport and deposition mechanisms. To answer these five questions, the following studies were made: - a literature review of the geodynamic setting for the Eromanga Basin and that of existing sandstone hosted uranium provinces. Data have been summarised in a series of space time plots - construction of a 3D map from publicly available datasets to better understand the basin architecture and fluid flow pathways - compilation of water chemistry to map potential fluid reservoirs and transport mechanisms - whole rock and multi element geochemistry together with detailed petrology, to understand uranium deposition mechanisms. A review of the geodynamic setting suggests that there are potentially three discrete mineralising events in the western portion the Eromanga Basin, which correspond to periods of known uplift and erosion. In the east there is potential for a single, long period, uranium mineralising event associated with the uplift of the Eastern Highlands. The 3D map of basin architecture shows that there are large, permeable sandstone packages that are bounded above and below by impermeable shales and that the sandstones are also exposed at the surface along the margins of the basin. This juxtaposition of lithologies is the most favourable architecture and fluid pathway for the formation of sandstone hosted uranium deposits, because fluids can enter the sandstone through outcropping aquifers and be contained above and below by aquitards. Groundwater hydrochemistry datasets show regional redox and pH fronts along the margins of the Eromanga Basin related to the movement of oxidised, acidic meteoric waters through porous sandstone layers. Uranium is commonly precipitated at redox gradients, particularly in areas close to a uranium source (i.e. sandstones with elevated background concentrations of uranium and/or uranium rich Proterozoic rocks exposed at the surface as in the case of Mt Isa and Mt Painter Inliers).