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.

This progress report follows a general report on the Wymah field by N.H. Fisher and C.L. Knight, submitted in June, 1942. It contains details concerning the development, ore structures, and mineral reserves of the Wymah wolfram mine.

The geology and ore reserves of the dolomite deposit near Wall's Siding are discussed in this report. The report should be read in conjunction with the report on "Limestone and Dolomite Deposits at Cow Flat and Wall's Siding, New South Wales" (Record 1947/090).

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

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.

These notes are supplementary to an earlier report (1948/016), and are designed to elucidate certain points brought up in that report. The issues of grade, workings, development, expenditure, production, and future prospects are generally discussed.

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 enquiry into this mine resulted from an application by the company for a loan from the Commonwealth to carry out exploration and development. The Tindalls Gold Mine has not been examined by the Bureau and unless this is done no definite statement about the ore possibilities of the property can be made. However, from past reports it seems likely that the deposit has a chance of producing a large tonnage of ore. Under present conditions and with the mining methods now employed, it is extremely doubtful whether ore of this grade could be mined at a profit. The ore reserves, mining, milling, costs, and general financial outlook with respect to the mine are discussed in this report.

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.