of overlying McArthur Basin sediments (or equivalents) - an evaporitic sequence occurring to the east of the EARUF but evidently erosionally stripped from the latter. The timing of 200°C regional temperatures inferred overlaps with the 1300-1550 ma ages of alteration associated with uranium mineralisation. Fluid inclusion (Ypma and Fuzikawa, 1980) and stable isotope data (Sun and Binns, 1983) indicate temperatures around 200°C for mineralisation/alteration - similar to the regional temperatures operative at this time. The range of U/Pb dates on uraninite also broadly coincide with the time during which the EARUF was at T > 150°C. Our fission track data thus support the contention (Johnston and Wall, this volume) that hydrothermal fluids responsible for mineralisation were part of large-scale and long-lived circulation systems following burial of the EARUF by Mid-Proterozoic sediments. Such circulation systems could involve the large volumes of fluid required to satisfy the fluid/ rock ratios inferred by Hedges, Wall and Bloom (this volume) for ore deposits in the EARUF without specialised heat sources. Mineral Number of Samples Average Age (m.y.) Precision U-cont. (ppm) Geological Track Retention Temperature 106 yr 108 yr (°C) Zircon 11 1415 ±88 55--110 < 253 < 179 Garnet 9 1346 ±76 45-- 83 < 205 < 159 Muscovite 11 1064 ±59 5-- 13 < 185 < 150 Biotite 1 932 ±49 ~ 8 < 170 < 140 Chlorite 6 713 ±44 3-- 9 < 160 < 130 Apatite 11 463 ±36 9-- 17 < 110 < 86 The brines responsible for alteration and mineralisation could have been derived by solution of evaporites in the Mid-Proterozoic sequence inferred to have been overlying_the EARUF between 1000-1500 ma. Such fluids would also have high S0I*~/H 2 S ratios i.e., be highly oxidised and capable of mobilising and transporting uranium (Hedges, Wall and Bloom, this volume). THE GEOLOGICAL DISTRIBUTION, MINING AND UTILISATION OF INDUSTRIAL GRADE MAGNETITE IN EASTERN AUSTRALIA E. Kreutzer1 and D. Nichol2 ^Steetley Industries Limited, Newcastle Steetley Industries Limited, Sydney Industrial grade magnetite ( F e ^ ) has a high specific gravity (5) and special magnetic properties and is particularly suitable as a dense medium in coal-washing, the process which removes shale and other rock fragments from the coal. The dense medium consists of a slurry of finely ground magnetite particles artificially suspended in water and is normally required to have a specific gravity between 1.3 and 1.9, that is, intermediate between the coal and the waste materials. Consumption of industrial grade magnetite for coal processing currently exceeds 80,000 tonnes yearly. 313