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.

The existence of wolfram in the deposit has been known since about 1915, and mining was carried out intermittently from that time until about 1938. It was not until June, 1951, when the deposit was visited by us, that the existence of scheelite in important quantity in the known ore was established. During this visit, also, a study of the structure of the deposit convinced us that, although only a little ore was exposed, considerable quantities of non-outcropping ore might be found. As magnetite is one of the gangue-minerals, a request was made for a magnetic survey. This survey was carried out by the Geophysical Section. Subsequent diamond drilling by Tungsten Consolidated Limited has shown that substantial bodies of scheelite and wolfram ore exist in the area under the structural conditions originally postulated; these conditions are outlined below. The geology of the deposits and the results of combined geological, geophysical, and diamond drilling investigations are discussed.

A geological survey of the Peko Gold Mine was conducted as part of the field activities of the Bureau of Mineral Resources in 1950. The objects of the survey were to study the factors localizing the ore, to suggest possibilities for the discovery of new oreshoots, and to plan a diamond drilling campaign to test these possibilities. J.F. Ivanac and B.P. Walpole mapped the geology of the mine. The plane table survey of the surface outcrops was carried out by E.M. Bennet. The results of the survey are presented in this report. History and production, general geology, economic geology, and the prospects of further discovery are discussed.

This geophysical survey was undertaken as part of a campaign by the N.S.W. Mines Department and the Commonwealth Bureau of Mineral Resources to explore the ore possibilities of the Cobar Mining Field. Tests, made in January 1947, on specimens of ore from the operating mines showed that some of the ore from the New Cobar and Chesney Mines exhibited appreciable magnetisation due to its pyrrhotite and possibly magnetite content. The survey was commenced in March, 1947 using the magnetic method only as a first method of attack. Watts Vertical Force Variometers Nos. 15887 and 16128 were used, the field work being carried out by the writers. The geology of the area, object of the survey, results, and recommendations for future drilling are discussed in this report. Two accompanying plans are included.

The present report gives an overview of the general geology and ore geology of the Blue Spec Mine. The main orebodies are described in some detail. General estimates of reserves and recommendations for future geological work are noted.

The operational history, orebody, workings, grade, tonnage, and financial considerations relating to the Chesney mine are discussed in this report. Two geological plans are included.

An examination of the New Cobar-Chesney-New Occidental area in 1947 concluded that the discordant contact between slaty and sandy beds in the area was a feature of major importance in ore localisation. Accordingly, an investigation was conducted in the vicinity of Cobar to determine whether a relationship existed between discordant contact and ore formation in that area, and to commence a detailed geological map on a regional scale of the Cobar-Nymagee mineral belt. The general geology, character of the discordant contact, stratigraphy, and economic geology of the area are discussed in this report.

The Great Cobar ore deposit was discovered in 1870. Production commenced in 1871 and since that date mining at Cobar has been more or less continuous. The field has produced copper, gold, and silver to the value of approximately £A27,000,000. Cobar has been the most important producer of copper in New South Wales, and in recent years, has also been the most important gold-mining centre. The Zinc Corporation Limited is carrying out, with the aid of the Bureau, an extensive geological and geophysical examination of the area, with the hope of finding other orebodies. The Bureau itself has extended geological mapping over an area of approximately 2,000 square miles in the Cobar-Nymagee-Canbelego district with the ultimate aim of discovering other ore deposits, or even fields of the Cobar type. In the Nymagee district, North Broken Hill Limited is also carrying out, in co-operation with the Bureau, an extensive exploration programme. The history, production, reserves and prospects of the New Occidental, Chesney, and New Cobar mines are discussed in this report.

The analyses of some Australian iron ores was undertaken. The results of these analyses are set down in this report. Results are given for each deposit by state.

Details concerning the reserves of iron ore in Australia have been tabulated in this report. The report provides estimates of the grade and probable reserves of ore for the known Australian deposits.