No abstract available

Predictive maps of the subsurface can be generated when geophysical datasets are modelled in 2D and 3D using available geological knowledge. Inversion is a process that identifies candidate models which explain an observed dataset. Gravity, magnetic, and electromagnetic datasets can now be inverted routinely to derive plausible density, magnetic susceptibility, or conductivity models of the subsurface. The biggest challenge for such modelling is that any geophysical dataset may result from an infinite number of mathematically-plausible models, however, only a very small number of those models are also geologically plausible. It is critical to include all available geological knowledge in the inversion process to ensure only geologically plausible physical property models are recovered. Once a set of reasonable physical property models are obtained, knowledge of the physical properties of the expected rocks and minerals can be used to classify the recovered physical models into predictive lithological and mineralogical models. These predicted 2D and 3D maps can be generated at any scale, for Government-funded precompetitive mapping or drilling targets delineation for explorers.

Legacy product - no abstract available

The Australian Calibration Line (ACL) , with a total gravity interval of 3 Gal, was established during 1970 between Laiagam in Papua New Guinea and Hobart in Tasmania. During 1973 the Australian Bureau of Mineral Resources and the USSR Geodesy and Cartography Survey made joint observations along the full length of the ACL. Measurements made with eight Soviet GAG-2 gravity meters established a gravity scale for Australia to an accuracy of 2.5 parts in 105. This scale and a datum of 979 671.86 mGal for Sydney A were adopted for Australia in 1973. The Soviet scale established for the ACL appears to be within 1 part in 104 of both the IGSN71 scale established for the Western Pacific Calibration Line by absolute determinations, pendulum measurements and international gravity meter comparisons, and the scale established for the Soviet Calibration Line by OVM pendulums. The Soviet scale for the ACL defines a milligal which is 1.5 parts in 104 larger than that defined by IGSN71 values for the ACL, and 5 parts in 104 larger than the 1965 Mean Australian Milligal that was used as an Australian milligal standard between 1965 and 1973. Both of these scales are partly based on Cambridge pendulum measurements made in Australia during 1950-51. These measurements are now thought to have been incorrect in scale. LaCoste, Romberg gravity meters have been used during six surveys along the whole or part of the ACL. The LaCoste observations have been reduced using the Soviet ACL scale and the new datum for Sydney A. The most probable values for airport gravity stations, calculated from the LaCoste results, have a precision of better than 0.01 mGal and are consistent to within experimental error with values calculated from the GAG-2 results. LaCoste observations reduced using the Soviet ACL scale give more accurate values for the gravity differences of the main intra-city ties and calibration ranges along the ACL.

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available