Victorian geophysical data

Contains TIFF images of airborne magnetics data obtained by the Australian Geological Survey Organisation (AGSO), the Geological Survey of Victoria (GSV) and various companies.

Seismic reflection imaging of mineral systems: Three case histories

Mineral deposits can be described in terms of their mineral systems, i.e., fluid source, migration pathway, and trap. Source regions are difficult to recognize in seismic images. Many orebodies lie on or adjacent to major fault systems, suggesting that the faults acted as fluid migration pathways through the crust. Large faults often have broad internal zones of deformation fabric, which is anisotropic. This, coupled with the metasomatic effects of fluids moving along faults while they are active, can make the faults seismically reflective. For example, major gold deposits in the Archaean Eastern Goldfields province of Western Australia lie in the hanging-wall block of regional-scale faults that differ from other nearby faults by being highly reflective and penetrating to greater depths in the lower crust. Coupled thermal, mechanical, and fluid-flow modeling supports the theory that these faults were fluid migration pathways from the lower to the upper crust. Strong reflections are also recorded from two deeply penetrating faults in the Proterozoic Mt. Isa province in northeastern Australia. Both are closely related spatially to copper and copper-gold deposits. One, the Adelheid fault, is also adjacent to the large Mt. Isa silver-lead-zinc deposit. In contrast, other deeply penetrating faults that are not intrinsically reflective but are mapped in the seismic section on the basis of truncating reflections have no known mineralization. Regional seismic profiles can therefore be applied in the precompetitive area selection stage of exploration. Applying seismic techniques at the orebody scale can be difficult. Orebodies often have complex shapes and reflecting surfaces that are small compared to the diameter of the Fresnel zone for practical seismic frequencies. However, if the structures and alteration haloes around the orebodies themselves, seismic techniques may be more successful. Strong bedding-parallel reflections were observed from the region of alteration around the Mt. Isa silver-lead-zinc orebodies using high-resolution profiling. In addition, a profile in Tasmania imaged an internally nonreflective bulge within the Que Hellyer volcanics, suggesting a good location to explore for a volcanic hosted massive sulfide deposit. These case studies provide a pointer to how seismic techniques could be applied during mineral exploration, especially at depths greater than those being explored with other techniques.

Deal Island Inset 1:250 000 topographic map

This map is part of the series that covers the whole of Australia at a scale of 1:250 000 (1cm on a map represents 2.5 km on the ground) and comprises 513 maps. This is the largest scale at which published topographic maps cover the entire continent. Each standard map covers an area of 1.5 degrees longitude by 1 degree latitude or about 150 kilometres from east to west and 110 kilometres from north to south. There are about 50 special maps in the series and these maps cover a non-standard area. Typically, where a map produced on standard sheet lines is largely ocean it is combined with its landward neighbour. These maps contain natural and constructed features including road and rail infrastructure, vegetation, hydrography, contours (interval 50m), localities and some administrative boundaries. The topographic map and data index shows coverage of the sheets. Product Specifications Coverage: The series covers the whole of Australia with 513 maps. Currency: Ranges from 1995 to 2009. 95% of maps have a reliability date of 1994 or later. Coordinates: Geographical and either AMG or MGA (post-1993) Datum: AGD66, GDA94, AHD. Projection: Universal Traverse Mercator (UTM) Medium: Paper, flat and folded copies.

Mount Marumba