A diverse range of mineralisation, including porphyry and epithermal deposits, intrusion-related gold and other metal deposits, iron oxide-copper-gold (IOCG) deposits and orogenic gold deposits all have linkages to crustal growth and magmatic arcs. Furthermore, all of these deposit types are associated with fluids containing H2O, CO2 and NaCl in varying and differing proportions. In all cases, it can be argued that magmas are a key source of hydrothermal fluids for these types of mineral system, and that subduction processes are critical to controlling fluid chemistries, the metal-bearing capabilities of the fluids and depositional processes. The differences on typical/bulk fluid chemistries between deposit types can be explained in part by differences in the P-T conditions of fluid segregation from its magmatic source. The most significant control here is the pressure at which fluid forms from the magma as this has a strong effect on fluid CO2/H2O values. This is clearly exemplified by the rare occurrence of readily detectable CO2 in deep porphyry systems (Rusk et al., 2004). On the other hand, fluid Cl contents (which strongly influence its base metal carrying capacity) are very sensitive to the magma's bulk composition. However, only some subduction-related magmas are fertile, and the differences do not seem to be due solely to variations in effectiveness of depositional processes. So what controls the volatile content of the magmas? Isotopic and other evidence, in particular for S and Cl, shows (unsurprisingly) that the greater contents of these elements in arc magmas compared to other melts is due to contributions from subducted materials, although there may be additional, lower crustal sources of Cl. Variations in the budget of volatiles subducted may thus play a role in controlling the chemistry of magmas and associated hydrothermal fluids, but variations within individual arcs suggests that again this is not the entire story.

Sediment-hosted Pb-Zn (SH Pb-Zn) deposits can be divided into two sub-types: 'clastic-dominated lead-zinc' (CD Pb-Zn) ores hosted in shale, sandstone, siltstone, mixed clastic or as carbonate replacement within a clastic dominated sedimentary sequence and Mississippi Valley-type (MVT Pb-Zn) ores that occurs in platform carbonate sequences, typically in a passive margin tectonic setting. The emergence of CD and MVT deposits in the rock record between 2.02 Ga, the age of the earliest known deposit of these ores, and 1.85-1.58 Ga, a major period of CD Pb-Zn mineralization in Australia and India, corresponds to a time after the 'Great Oxygenation Event' (GOE) ca 2.4 to 1.8 Ga. Contributing to the blooming of CD deposits at ca 1.85-1.58 Ga was the following: a) enhanced oxidation of sulfides in the Earth's crust that provided sulfate and lead and zinc to the hydrosphere; b) development of major redox and compositional gradients in the oceans; c) first formation of significant sulfate-bearing evaporites; d) formation of red beds and oxidized aquifers: e) evolution of sulfate-reducing bacteria; and f) the formation of large and long-lived basins on stable cratons. A significant limitation imposed on interpreting the secular distribution of the deposits is that presently, there is no way to quantitatively evaluate the removal of deposits from the rock record through tectonic recycling. Considering that most of the sedimentary rock record has been recycled, probably most SH Pb-Zn deposits have also been destroyed by subduction and erosion or modified by metamorphism and tectonism so that they are no longer recognizable. Thus, the uneven secular distribution of SH Pb-Zn deposits reflects the genesis of these deposits, linked to Earth's evolving tectonic and geochemical systems, as well a record severely censored by an unknown amount of recycling of the sedimentary rock record.

Metallogenic, geologic and isotopic data indicate secular changes in the character of VHMS deposits relate to changes in tectonic processes, tectonic cycles, and changes in the hydrosphere and atmosphere. The distribution of these deposits is episodic, with peaks at 2740-2680 Ma, 1910-1840 Ma, 510-460 Ma and 370-355 Ma that correspond to the assembly of Kenorland, Nuna, Gondwana and Pangea. Quiescent periods of VHMS formation correspond to periods of supercontinent stability. Large ranges in source 238U/204Pb that characterize VHMS deposits in the Archean and Proterozoic indicate early (Hadean to Paleoarchean) differentiation. A progressive decrease in - variability suggests homogenisation with time of these differentiated sources. Secular increases in the amount of lead and decreases in 100Zn/(Zn+Pb) relate to an increase in felsic-dominated sequences as hosts to deposits and an absolute increase in the abundance of lead in the crust with time. The increase in sulfate minerals in VHMS deposits from virtually absent in the Meso- to Neoarchean to relatively common in the Phanerozoic relates to oxidation of the hydrosphere. Total sulfur in the oceans increased, resulting in an increasingly important contribution of seawater sulfur to VHMS ore fluids with time. Most sulfur in Archean to Paleoproterozoic deposits was derived by leaching rocks below deposits, with little contribution from seawater, resulting in uniform, near-zero-permil values of 34Ssulfide. In contrast the more variable values of younger deposits reflect the increasing importance of seawater sulfur. Unlike Meso- to Neoarchean deposits, Paleoarchean deposits contain abundant barite, which is inferred to have been derived from photolytic decomposition of atmospheric SO2 and does not reflect overall oxidised oceans. Archean and Proterozoic seawater was more salty than Phanerozoic, particularly upper Phanerozoic, seawater. VHMS fluids ore fluids reflect this, also being saltier in Precambrian deposits.

During the 1950 Field Season three radiometric anomalies were located by geophysical methods on a low hill situated between 1,300 and 2,000 feet east of White's Deposit. This area is known as White's Extended Prospect. In 1951 geological mapping on a scale of 40 feet to an inch was undertaken and this was followed by costeaning and diamond drilling. Owing to other commitments in the Rum Jungle area the explanatory programme and mapping in the White's Extended area has not been completed.

This report describes a geophysical survey made in May 1952 and August 1953 at the Silver Valley mine workings, near Inverell, N.S.W. From the workings there is evidence of mineralisation along a well-defined fissure and one ore shoot has already been partly developed. The survey was made in an attempt to locate other ore shoots of sufficient size to warrant mining operations. Self-potential, magnetic and electromagnetic methods were used in the survey. The self-potential method showed a well-defined anomaly on the eastern extension of the fissure, indicating that a small body of sulphides may exist there with its centre about 300 feet east of the known ore shoot. The magnetic and electromagnetic results showed no pronounced anomalies which could be correlated with any defined ore shoot. Recommendations are made as to how the self-potential anomaly could best be tested. These comprise sinking a shaft at the centre of the anomaly, extending an existing adit, or driving a new adit from a point nearer the anomaly.

A geological investigation of the Maranboy Tin Field was commenced by officers of the Bureau of Mineral Resources in May, 1951. The object of the survey is, primarily, to obtain a detailed preliminary assessment of the potential ore reserves of the field. Geological mapping and sampling of the major lode lines has been carried out in an attempt to determine the features which control ore deposition and to enable estimates to be prepared of the grade and tonnage of ore per vertical foot, which may be expected from these lode lines. The main emphasis of this work during the 1951 field season was on the major producing lines in what has been called the Southern Field, the Main Lode and part of the Stannum King lode. In addition to this programme, an area of approximately nine square miles was mapped in detail using aerial photographs. Approximately 1,000 square miles of the area surrounding Maranboy was mapped on a regional basis. The history of the field, general geology, and the geology of the individual lodes are discussed in this report. The accompanying maps are enclosed.

The period 7th to 28th January, 1951 was spent at Selwyn by the writer: approximately one week was spent in preparing a semi-regional map at a scale of 1 inch to 400 feet; one week was given to mapping a smaller area at a scale of 1 inch to 40 feet. Level plans have been constructed showing what are considered to be the broad outlines of ore arrangement and structure and a number of sections have been constructed. Nineteen plans and sections illustrate this report. Twelve typical ore and rock specimens were studied in thin section and the information obtained has been incorporated in this report. An account of the regional geology of the prospect and the geology of the ore deposits is given in this report.

Mining and exploration activities and geological investigations carried out in the Rum Jungle area during 1951 and 1952 have provided important results and basic information concerning the known uranium deposits, and indicate the presence of numerous interesting prospects requiring further investigation. Details of the results and the nature of the investigations are given in the following pages.

The Kangaroo Caves zinc-copper deposit in the Archaean Panorama District in the northern Pilbara Craton, Western Australia contains an Indicated and Inferred Mineral Resource of 6.3 million tonnes at 3.3% zinc and 0.5% copper. The Kangaroo Caves area is characterised by predominantly tholeiitic volcanic rocks of the Kangaroo Caves Formation, which is overlain by turbiditic sedimentary and volcanic rocks of the Soanesville Group. Zinc-copper mineralisation is hosted mainly by the regionally extensive Marker Chert, the uppermost unit of the Kangaroo Caves Formation, and structurally controlled by D1 synvolcanic faults. The upper area of the deposit is characterised by quartz-sphalerite ± pyrite ± baryte ± chalcopyrite, whereas the lower area contains mainly chlorite-pyrite-quartz-carbonate-sericite ± chalcopyrite ± sphalerite. Laser ablation inductively coupled plasma mass spectrometry analyses show that cobalt-nickel ratios in pyrite are significantly greater in the upper, zinc-rich area (median copper/nickel = 0.4) of the deposit than the lower, zinc-poor area (median copper/nickel = 5). Structural analysis of the Kangaroo Caves area combined with Leapfrog modelling of ore and trace element distribution shows that the deposit is predominantly an elongate sheet of zinc mineralisation (-1%), which plunges ~30° to the northeast and is approximately 1000 metres in length. The morphology of the Kangaroo Caves deposit was retained from its original formation, despite rotation during the D2 event. Variations in hydrothermal alteration assemblages, including the copper and nickel contents of pyrite within the deposit and underlying dacite, are interpreted to be the result of variations in the influx and mixing of seawater with upwelling volcanogenic fluids during zinc-copper mineralization. At the Kangaroo Caves area the cobalt-nickel ratio of pyrite can be used as an exploration vector towards high-grade zinc-copper mineralization.

A review of mineral exploration activity in Australia for 2009. This extended edition includes coverage reported in the shorter edition.