Identifying geothermal resources typically requires time-consuming extensive geophysical surveys and deep drilling, which are costly and logistically challenging. This study illustrates the use of readily available shallow groundwater temperature data combined with surface air temperature records as a fast, low-cost, exploration screening tool for geothermal anomalies in deep sedimentary basins. The data were collated from existing piezometers used to monitor water-table fluctuations in groundwater monitoring wells, which are far more common than the bores typically used for geothermal temperature measurements. Geothermal anomalies can be identified by spatial analysis of the difference between the phreatic surface temperature and long-term averaged air temperature data. The study evaluates the workflow using known deep geothermal anomalies in two geologically distinct sedimentary basins: the onshore Perth Basin in Western Australia and the Hunter Valley in New South Wales. The analysis demonstrates that the widely available and commonly acquired hydrogeological data, along with average surface air temperature data, can be used for exploration for deeper geothermal anomalies. While the data are commonly measured to provide information about subsurface water levels, collating a more comprehensive national database of borehole temperature data would further facilitate geothermal exploration programs that are seeking deep sources of heat for electricity generation or shallow sources of heat for ground-source heat pumps.

The Green Scrub Basalt is located on the western side of the Lapstone Structural Complex (LSC) in the Sydney Basin. It was initially mapped as a neck, but more recently it has been viewed as a flow associated with other basalts in the Blue Mountains Volcanic Province. As a consequence, it was inferred that the age of the LSC was at least the age of the basalt, dated at 18.8 Ma. This study has carefully mapped the Green Scrub Basalt and re-establishes it as a neck. As such it does not constrain the age of the LSC. Local dips across the LSC show that the structure of the LSC is likely to be a fault propagation fold above a west-dipping thrust. The structure may have been initiated in the Neogene when pollens were deposited at nearby Mountain Lagoon.

This interpretation of the Cambrian–Ordovician history of the southern Tasmanides on mainland Australia examines: (i) the Selwyn Block of central Victoria; and (ii) the Delamerian Arc, stretching from Victoria into South Australia, and then into far northwestern NSW. The zig-zag belt of Delamerian arc volcanics may have existed with gaps from ca 540 Ma in Victoria (Stavely Arc), but the 510–500 Ma upper part that formed during regional ca 515 to 500 Ma extension is best known. This extension generated back-arc rift basins west of, and rift volcanics on the site of the old arc. Destruction/inversion of these rift basins at ca 500 Ma, reflects the main Delamerian Orogeny. From 510 Ma, the outboard Selwyn Block had migrated northwest towards the east Gondwana margin from a location in a marginal sea between that margin and an inferred east-dipping subduction zone. It had collided with the 518–510 Ma fore-arc of that subduction zone, with ophiolite obduction over by 510 Ma. The Selwyn Block, with overthrust ophiolites preserved in the Heathcote Fault Zone and Governor Fault Zone, remained outboard of Gondwana in open ocean, covered by basalt, chert and shale, with the last two distal from the continental margin, from ca 510 to 450 Ma until it was accreted along with the Bendigo basin at ca 443 Ma. The Selwyn Block is thus interpreted as a submarine plateau. In contrast, the West Tasmania Terrane is a continental block that was accreted at ca 500 Ma. This accretion removed an obstacle to the deposition of the turbidites into marginal ocean basins either side of the Selwyn Block from ca 500–490 Ma to 443 Ma.

This study examines the fifth member of the Xujiahe Formation (Xu 5) in the central Sichuan Basin. Various experimental analyses were carried out to evaluate pore structure, micro-heterogeneity, movable fluid saturation and their influencing factors across different lithofacies. (1) The fine-grained sedimentary rocks of the Xu 5 Member can be classified into three lithofacies: pure shale (SH), shale with silty lamination (SS) and muddy siltstone (MS). The pore shapes in the Xu 5 Member are mainly narrow fissure-like and bottle-shaped, with variations in pore-size distribution across lithofacies. Lithofacies SH and SS primarily consist of micropores (<2 nm) and mesopores (2–50 nm), while lithofacies MS primarily develops mesopores and macropores (>50 nm). (2) An increase in the volume and specific surface area of mesopores and micropores increases the complexity of the pore structure, resulting in greater reservoir heterogeneity. In contrast, a higher macropore content decreases micro-heterogeneity within the reservoir. An increase in clay minerals and siderite significantly enhances reservoir micro-heterogeneity, while quartz has a detrimental effect. Total organic carbon has no significant effect on micro-heterogeneity. (3) The movable fluid saturation in the reservoir is affected by both pore structure and micro-heterogeneity, greater micro-heterogeneity and more complex pore structures lead to reduced fluid mobility. (4) The depositional environment and hydrodynamic conditions are key factors affecting reservoir micro-heterogeneity and fluid mobility. Increased proximity to deltas during sedimentation, combined with stronger hydrodynamic forces, results in coarser and more rigid reservoir grains, leading to reduced micro-heterogeneity and improved pore structure and fluid mobility.

Hyperspectral logging of diamond drill core has become a routine technique in state drill core repositories across Australia. Manually logging grainsize can be difficult and is a subjective and labour-intensive process that can lead to inconsistencies. This study investigates the application of spectral calculations to automate grainsize estimation using the primary and secondary Reststrahlen features of quartz and carbonate within the 6500–14 400 nm range. Several spectral methods were tested, including automated relative abundance of quartz, feature extraction, polynomial fitting and arithmetic expressions. Data processing was performed using The Spectral Geologist™ 8 software, which automatically generated results for the relative abundance of quartz. This metric proved valuable for identifying lithological boundaries and tracking changes in quartz content, aiding interpretation of depositional environments. Although the feature-extraction method initially produced unexpected spectral outputs, it uncovered variability within lithological units that could be used for further classification. Polynomial fitting at 8190 nm did not correlate well with geological logging, but the spectral fitting at 8630 nm showed excellent agreement with geological observations. Two arithmetic methods for calculating quartz and carbonate grainsizes both performed accurately; however, the quartz grainsize scalar did not provide additional value compared with the other approaches. This paper aims to: (1) showcase the use of thermal infrared spectral features for rapid and reliable grainsize estimation and (2) describe simple spectral calculations geologists can apply during core logging. The results indicate that grainsize estimation can now be automated across a variety of platforms using the spectral algorithms detailed herein. This approach shows potential for the ability to create or improve existing grainsize logs where they exist in historic datasets. These methods, particularly the 8630 nm trough for quartz, also offer significant potential for accurate lithological differentiation and can be applied across different mineral systems, including those associated with economic mineralisation.

All information about the age and origin of gold mineralisation comes from associated bedrock and accessory minerals. Native gold also preserves the information about its formation but remains under-studied owing to the small size and scarcity of visible gold grains, commonly recrystallised nature of larger placer nuggets, and analytical difficulties requiring specific protocols and dedicated equipment. As a result, very few analytical studies have been conducted to investigate the Pb isotope model age and Pb source of Archean placer gold nuggets. In this work, we develop and test Pb isotope techniques to study small placer gold nuggets (some with galena micro-inclusions) from the Archean Kurnalpi Terrane in the Eastern Goldfields Superterrane. The results show that galena micro-inclusions in gold display more primitive Pb isotope ratios compared with native gold, corresponding to the Archean model age of 2.66 Ga. Native gold nuggets display slightly more radiogenic Pb isotopic ratios with model ages ranging from 2.62 up to 2.44 Ga, for the least altered gold samples, probably reflecting an addition of radiogenic Pb from U decay since their formation. The source µ (238U/204Pb) values for the less radiogenic samples range from 8.17 to 8.28, similar to values of galena from volcanogenic massive sulfide deposits (Teutonic Bore camp and Nimbus) in the region, indicating mostly a juvenile, predominantly mantle-derived source of Pb. The most altered and recrystallised gold nuggets display more radiogenic 206Pb/204Pb up to 17.81. These values fall along a linear trend towards Pb isotope compositions that may reflect the mobility of Pb in regolith during gold recrystallisation event(s). Although nuggetty gold mineralisation is unknown in the local sub-economic orogenic gold deposits, our study suggests that gold nuggets in the Kurnalpi Terrane formed in the late Archean and variably underwent later alteration and Pb addition during uplift, erosion, deposition and regolith forming processes.

Lithology, alteration and Au mineralisation characteristics of the McPhillamys gold deposit in central NSW have proved difficult to interpret owing to structural overprinting. Previous models for the genesis of Au mineralisation include syngenetic (late Silurian Au-rich volcanic massive sulfide; VMS) or epigenetic (Carboniferous orogenic Au). We combine extensive new HyLogger spectral data (SWIR and TIR), petrographic analysis, geochronology and isotopic data to determine the alteration/mineralisation paragenesis, alteration zonation and effects of lithological control on mineralisation by using both downhole and broad-scale 3D mineralogical characterisation. The mineralisation at McPhillamys is stratabound within a coarse andesitic/dacitic volcaniclastic package. Alteration involved the development of an initial potassic core (microcline (ex-adularia)–quartz–pyrite) associated with the mineralised volcaniclastic package at the centre of the orebody and extending into the overlying non-mineralised andesitic volcanic/volcaniclastic package north and south of the mineralised zone. Propylitic-style alteration (albite–pyrite–chlorite–carbonate ± epidote) forms an outer shell to the mineralisation, except at the northern and southern extents of the mineralised trend. White mica, chlorite, feldspar and carbonate all display consistent and mappable compositional variation between mineralised and non-mineralised sequences. It is difficult to decipher the early history of the deposit and geochronology (U–Pb and Ar–Ar), presented in this study, is unable to distinguish if mineralisation and alteration developed just after deposition of the host sequences during the latest Silurian (ca 423 Ma) with extensive recrystallisation during both Tabberabberan (ca 390 Ma) and Kanimblan (ca 350 Ma) orogenic events, or if mineralisation developed solely during the Tabberabberan Orogeny (ca 390 Ma) with extensive recrystallisation during the Kanimblan Orogeny (ca 350 Ma). We suggest the mineralogy, broad spatial distribution (700 m long, 250 m width, and up to 700 m depth) and paragenesis of alteration and mineralisation at McPhillamys are consistent with a deformed late Silurian lithologically controlled low-sulfidation epithermal, or potentially a shallow water (subsea-floor) Au-rich VMS system.

Greenstone and intrusive rocks of the Archean Kalgoorlie–Kurnalpi Rift (KKR), Western Australia, contain widespread examples of sodic and sodic–calcic alteration that formed from synvolcanic times to the latest stages of orogenesis. In many cases, these alteration types are directly or indirectly associated with gold mineralisation. Examples follow. (i) The historic, structurally controlled Yundamindera gold deposits, hosted by the synvolcanic Danjo tonalite, are associated with sodic–calcic alteration in the south and calc-potassic alteration in the north. Semi-conformable, seafloor alteration, including sodic alteration (albitisation), is well developed in country rocks around the Danjo batholith. The geological setting and high-temperature (>500 °C) alteration assemblages at Yundamindera suggest that the gold deposits formed within the synvolcanic thermal anomaly represented by the Danjo batholith. (ii) Ultramafic-hosted albitites in regional shear zones and intervening low-strain domains formed during regional deformation and formed rheological anomalies that localised a later gold-bearing hydrothermal ore fluid. (iii) Feldspar porphyry-hosted gold at the Janet Ivy deposit, Binduli, is hosted by quartz veins and their sodic (albite–carbonate) alteration halos. The formation of hydrothermal albite, rather than white mica, may reflect the high Al/(Mg + Fe + Cr) bulk composition of the host rock. (iv) Metasomatic aureoles of hydrothermal alteration, including sodic and/or sodic–calcic alteration, are developed around some small, high-level alkalic and calc-alkaline intrusions. Although these metasomatic aureoles are mostly barren, they are overprinted by gold (±copper) lodes at Karari–Whirling Dervish (Au) and Burns (Cu–Au) deposits. Formation of these lodes was caused by a high-temperature (500 °C), oxidised and potassic ore fluid derived from the spatially associated intrusion. These later fluids deposited hydrothermal biotite and K-feldspar with close links to pyrite and gold. These examples illustrate the diversity of geological contexts for sodic and sodic–calcic alteration in the KKR. Some products of this alteration are direct hosts for gold (Yundamindera south, Janet Ivy), whereas others are a precursor event to gold mineralisation. The latter examples of sodic and sodic–calcic alteration may act simply as a rheological anomaly (albitite–ultramafic association) or comprise the early parts of an extended magmatic–hydrothermal event that evolved to deposit gold and pyrite in association with biotite and K-feldspar (Karari–Whirling Dervish, Burns).

The Cambrian–Ordovician Wagonga Group of the Narooma and Batemans Bay regions, coastal southeastern New South Wales in the southeastern Lachlan Orogen, consists of oceanic rocks that were affected by major deformation during the Late Ordovician to early Silurian Benambran Orogeny. At Narooma, the stratigraphy is based on Cambrian–Ordovician conodonts in the Narooma Chert, which has a lower part containing bedded chert and interbedded siliceous mudstone and an upper part of black siliceous mudstone and interbedded white–grey mudstone/siltstone. The Narooma Chert is associated with the Kianga Basalt that includes pillow lava but also common mafic breccia/conglomerate. Overlying the upper Narooma Chert is the unfossiliferous Bogolo Formation containing mudstone and mélange of potentially diverse origins. The structure is complex with tight-isoclinal folding, mélange and potential thrust repetition of the succession, and is faulted against the Ordovician Adaminaby Group. The same stratigraphy is mapped at Batemans Bay in addition to interfingering of the Narooma Chert and Adaminaby Group turbidites at Burrewarra, Melville and Pretty points. The late Cambrian limestones at Burrewarra Point are associated with mafic breccia/conglomerate and are interpreted as ocean-island submarine slide deposits analogous to those on the modern deep-sea floor surrounding the Hawaiian Islands. These deposits are overlain by Ordovician quartz turbidites and Narooma Chert. Around Batemans Bay quartz turbidites and lithic turbidites are interstratified in sections of the Narooma Chert attesting to the interplay of the Ordovician turbidite fan and its interaction with ocean-island sources. The ancient ocean basin was closed by subduction in the Benambran Orogeny and associated with the later phase of magmatic activity in the Macquarie Arc. A subduction complex setting for this final accretionary deformation has been proposed but lacks a well-developed forearc basin compared with other subduction complex-forearc basin couplets of ­circum-Pacific orogenic belts.

The Malan loess Q3 has been used to extract the true shape of particles from the loess shear failure surface based on direct shear experiments and scanning electron microscopy experiments, and establishes shear failure models with different particle roundnesses using the discrete element method. The impact of changes in particle roundness on shear stress, cohesion and the internal friction angle of the model was analysed at the macro level, and the impact of changes in particle roundness on particle contact force was analysed at the micro level. The results showed that the decrease in particle roundness resulted in an increase in the shear stress required for model shear failure, with a smaller increase at low normal stress and a larger increase at high normal stress. The decrease in particle roundness increases the cohesion and internal friction angle of the model, with a smaller increase in cohesion and a larger increase in internal friction angle. The reduction in particle roundness will affect the magnitude and direction of particle contact force, and the effect is more pronounced under high normal stress.