The Record contains extended abstracts to accompany presentations at the GOMA (Gawler Craton-Officer Basin-Musgrave Province-Amadeus Basin) seismic and MT workshop, Adelaide 25 November 2010.

Legacy product - no abstract available

The Sedimentary basins of eastern Australia project undertook structural and sequence stratigraphic mapping of a regional grid of seismic reflection data in the Bowen, Gunnedah and Surat Basins (usually 4 seconds two-way travel time data, with about 15,000 line km of data on about 1200 individual seismic lines). The seismic mapping was used to define the interplate and intraplate tectonic events that have helped to create the accommodation space and also to define the stratal geometry of the sedimentary units. Thus, the mapping provided the overall geometry of the basin system as well as the geometry of several of the sequence boundaries, resulting in the development of a new sequence stratigraphic framework for the basins. These results were also compiled into a series of structure contour and isopach maps, which have been used to build a 3D geological map of the Bowen Gunnedah and Surat Basins.

The granite-greenstone terrains of the Eastern Goldfields Province, Yilgarn Craton, are extremely important as a major Australian gold province. The Kalgoorlie region, in particular, hosts several world class gold deposits. A grid of deep seismic reflection lines was acquired in 1999 to examine the three-dimensional geometry of the major structural features in the region within an area of the Kalgoorlie - Ora Banda region of the Eastern Goldfields Province, Yilgarn Craton. These seismic lines presented an ideal opportunity to further develop our 3D understanding of this highly mineralised granite-greenstone terrain. The seismic grid tied into the earlier 1991 regional deep seismic traverse and the more recent 1997 regional and high-resolution profiles acquired in the region. It covered and area approximately 50 km square that extended to a depth of approximately 35 km (ie the base of the crust in this area). The resulting seismic grid was well suited to the development of a three-dimensional model of the region that could be used to investigate the spatial relationships of the greenstones and the granites. The 3D geological model of this region was built using a 3D modelling software package, GOCAD(r). It was built using surface geological data and geological interpretations of the region's deep and high-resolution seismic reflection profiles. The latter seismic interpretations were constrained by gravity modelling.

No abstract available

In 1999, a grid of five deep seismic reflection traverses was acquired within an area approximately 50 km wide by 50 km long in the Kalgoorlie Region, Eastern Goldfields Province, Yilgarn Craton. The grid tied into the existing 1991 deep seismic reflection transect (EGF1) and the 1997 high resolution and regional seismic profiles acquired by the Australian Geodynamics Cooperative Research Centre (AGCRC) and Kalgoorlie Consolidated Gold Mines (KCGM). The data were acquired to examine the geometry of the major structural features of the region, particularly the highly mineralised Bardoc Shear, and to provide three-dimensional information on granites-greenstones relationships. This paper describes the geometry of the crust and, in particular, the geometry of the granite and greenstones above the prominent regional detachment surface that occurs at about 4-6 km depth, though in one place it may extend to a depth of approximately 11 km. From the seismic, the Bardoc Shear is confirmed as west dipping and a non-planar crustal penetrating structure. The gravity modelling suggests that there is no need for the large volumes of mafic or ultramafic material previously assumed to be at depth, apart from those mapped at the surface and projected to depth.

Labuan Basin lies in deep water adjacent to the eastern Kerguelen Plateau. The basin is about 800 km long and 300 km wide and contains up to 4.5 km of sediment. A general lack of geophysical data and geological samples in this remote basin have inhibited understanding of its stratigraphy and crustal origin. Our new seismic stratigraphic interpretation of the Labuan Basin is based on deep multichennel seimic data collected by Geoscience Australia in 1997 during "Rig Seismic" surveys 179 and 180 intergrated with results of Ocean Drilling Program (ODP) Leg 183 (1998-1999)

Seismic line 07GA-IG2, described here, forms part of the Isa-Georgetown-Charters Towers seismic survey that was acquired in 2007. The seismic line is oriented approximately east-west and extends from east of Croydon in the west to near Mt Surprise in the east (Figure 1). The acquisition costs for this line were provided jointly by the Geological Survey of Queensland and Geoscience Australia, and field logistics and processing were carried out by the Seismic Acquisition and Processing team from Geoscience Australia. Three discrete geological provinces have been interpreted on this seismic section (Figure 2). Two of these, the Numil and Abingdon Provinces, only occur in the subsurface. The upper crustal part of the seismic section consists of the Paleo- to Mesoproterozoic Etheridge Province, which here includes the Croydon Volcanic Group in the western part of the Province. In this east-west profile, the crust is essentially two-layered, with a strongly reflective lower crust defining the Numil and Abingdon Provinces and a less reflective upper crust being representative of the Etheridge Province.

Potential field data were used to constrain or support the geological interpretations of the 2006 and 2007 North Queensland seismic data. Potential field forward modelling, potential field inversions and worms of potential field data all supported the interpretations of the seismic data.

A ~400 km long deep crustal reflection seismic survey across central Victoria, Australia, was carried out in 2006 as a collaborative project between the pmd*CRC, Geoscience Australia, the Victorian Government, Ballarat Goldfields NL, Gold Fields Australasia Pty Ltd and Perseverance Corporation Ltd, using the facilities of the National Research Facility for Earth Sounding (ANSIR). The aim was to cross several Neoproterozoic-Palaeozoic basement zones and provide information on the crustal architecture, particularly across the highly prospective Palaeozoic rocks occurring along strike to the north of the major Victorian goldfields, such as Bendigo. In the west, the Moyston Fault is a major east-dipping planar fault near the eastern edge of the Grampians-Stavely Zone, which was probably the eastern margin of continental Australia in the Cambrian. It cuts through the entire crust to the Moho. The Stawell Zone, immediately east of the Moyston Fault, has the geometry of a doubly vergent wedge. The boundary between the Stawell Zone and the Bendigo Zone farther to the east is the Avoca Fault, which appears to be a west-dipping listric fault that links to the Moyston Fault at a depth of about 22 km, forming a Y-shaped geometry. Internal faults in the Stawell and Bendigo zones are almost entirely west-dipping listric faults, which cut deep into the highly reflective lower crust, interpreted to be stacked ? Cambrian oceanic crust. Previous models advocating the presence of a mid-crustal detachment are not supported by these deep crustal scale faults. The boundary between the Bendigo and Melbourne zones, the Heathcote Fault Zone, forms a zone of strong west-dipping reflections about three kilometres wide to a depth of at least 20 km, and possibly to the Moho. The fault zone is complex and contains a boninite-tholeiite association along with blueschists in a serpentinite-matrix melange, and oceanic sedimentary rocks. The Melbourne Zone contains a deformed sedimentary pile up to 15 km thick, and contains previously unrecognised north-dipping listric faults, interpreted to be thrusts. The Governor Fault separates the Melbourne Zone from the Tabberabbera Zone and contains similar rocks to the Heathcote Fault Zone. Near the surface, the Governor Fault dips to the north at about 10°. The seismic character of the lower crust below the Melbourne Zone (the "Selwyn Block") is significantly different to that observed below the Bendigo and Stawell zones, and consists of several very strong subhorizontal reflections about 5-6 km thick starting at about 18 km depth, with a less reflective zone below it. In summary, the deep seismic data across central Victoria has allowed the geometry of the rocks and structures mapped at the surface to be projected through the entire crust, thus providing important constraints to test previous tectonic models.