Gold deposits in the Archaean Eastern Goldfields Province in Western Australia were deposited in greenstone supracrustal rocks by fluids migrating up crustal scale fault zones. Regional ENE-WSW D2 shortening of the supracrustal rocks was detached from lower crustal shortening at a regional sub-horizontal detachment surface which transects stratigraphy below the base of the greenstones. Major gold deposits lie close to D3 strike slip faults that extend through the detachment surface and into the middle to lower crust. The detachment originally formed at a depth near the plastic-viscous transition. In orogenic systems the plastic-viscous transition correlates with a low permeability pressure seal separating essentially lithostatic fluid pressures in the upper crust from supralithostatic fluid pressures in the lower crust. This situation arises from collapse in permeability below the plastic-viscous transition because fluid pressures cannot match the mean stress in the rock. If the low permeability pressure seal is subsequently broken by a through-going fault, fluids below the seal would flow into the upper crust. Large, deeply penetrating faults are therefore ideal for focussing fluid flow into the upper crust. Dilatant deformation associated with sliding on faults or the development of shear zones above the seal will lead to tensile failure and fluid-filled extension fractures. In compressional orogens, the extensional fractures would be sub-horizontal, have poor vertical connectivity for fluid movement and could behave as fluids reservoirs. Seismic bright spots at 15-25 km depth in Tibet, Japan and the western United States have been described as examples of present day water or magma concentrations within orogens. The likely drop in rock strength associated with overpressured fluid-rich zones would make this region just above the plastic-viscous transition an ideal depth range to nucleate a regional detachment surface in a deforming crust.

<p>Geoscience Australia conducted equipment tests at Millmerran, Queensland, using the newly acquired Sercel SN368 data acquisition seismic system. The equipment operated satisfactorily and proved to be versatile.<p><b>Raw data for this survey are available on request from clientservices@ga.gov.au - Quote eCat# 74967</b>

Field tests were conducted on 11 March 1974 in Waiaal Victoria to compare the seismic efficiency of Molanite, TNT, and-Anzite Blue. Ueismic energy p:enerated by equal amounts of each explosive was recorded in identical conditions, and the amplitudes of the refracted and reflected waves were measured and compared. The comparisons indicated that Molanite and Anzite Blue were equally efficient whereas TNT was about 10 percent less efficient. No significant difference was observed in the character of the seismic energy generated by any of the explosives tested.

Seismic reflection survey has been conducted to help identify the possible oil-bearing structures, which were revealed by two residual gravity anomalies in a geophysical survey made by the Bureau of Mineral Resources. Good reflections were obtained in some parts of the area, but the quality was not consistent. The seismic results appear to confirm a small closure near one of the gravity anomalies. No definite closure is shown near the other anomaly.

A seismic reflection traverse on portion of the Giralia anticline was conducted by the Bereau of Mineral Resources (BMR). This work constitutes a part of a general programme of investigation which the BMR, Geology and Geophysics, has been carrying out on Permit areas held by Ampol Petroleum Ltd. in this area. The purpose of the survey is to idenfy the proposed geology structure in this region based on the previous geology surveys.

A refleotion traverse was shot across the centre part of the Giralia Anticline in the Carnarvon Basin of Western Australia, in an attempt to verify the unconformity between Mesozoic and Palaeozoic sediments shown by a previous traverse across the northern part of the anticline. Shallow seismic events recorded were of good quality and correlated very well with surface geology. They also indicated two faults in places where steep dips in surface beds might, by anaJogy with the northern end, be expected. Deep events were in general of poor quality and inconsistent. However, over approximately a mile of the traverse, they were of good quality and indicated nonconformity with the shallow events.

A reconnaissance seismic reflection and refraction survey in the East Otway Basin, Victoria, was carried out by the Bereau of Mineral Resources from mid-February to mid-June 1967. The objective of the survey was to determine whether the gravity low areas of the Torquay Embayment and Port Phillip Sub-Basin in the eastern part of the Otway Basin contain thick Cretaceous sediments like those which has shown potential hydrocarbon source and reservoir characteristics in the western part of the Otway Basin. Nine reflection and five refraction traverses were recorded in the gravity low areas of the Barwon Trough and Port Phillip Sub-basin. Single-coverage reflection results of variable quality were obtained. Evidence for the presence of Tertiary section is provided by shallow reflections of good to fair quality, but the evidence for Cretaceous sediments is tenuous because of the poor quality of the deeper reflections, some of which may be multiples. The presence of several faults, onlappings and pinch-outs is also indicated. The refraction results are considered unreliable because of the difficulty of interpreting the discontinuous profiles and because of the mapped and suspected faults and pinch-outs in the sections.

A reflection seismic survey was made in an area north and north-west of Roma, to find whether there are any domal structures associated with the known occurrences of oil and gas. The general quality of the reflections recorded was poor, and no evidence of an anticline or basement high was found at Hospital Hill or Block 1 6 where oil and gas have been previously found. No targets for drilling were found and further seismic work is not at present recommended.

<p>Geoscience Australia conducted a seismic reflection, seismic crustal refraction and gravity survey in southeastern Queenland from August to November 1986. The primary objective of the survey was to complete seismic reflection coverage in the Dalby-Toowoomba area between Traverse 14 and Traverse 16 recorded during the BMR S.E. Queensland seismic survey in 1984. Secondary objectives, subject to survey progress included recording additional seismic reflection data east of Traverse 16 (1984). Overall the survey objectives would allow the completion of a continuous deep crustal seismic reflection profile of 1110 km length across southern Queensland, the basis of a lithospheric transect study in the southern region of Queensland. The survey obtained a total of 181 km of six-sixteen fold Common-Middle-Point (CMP) seismic reflection data in the Beenleigh, Darling Downs and Mitchell areas, using the Sercel SN368 seismic acquisition system.<p><b>Raw data for this survey are available on request from clientservices@ga.gov.au - Quote eCat# 74962</b>

The Oaklands-Coorabin Coalfield in the Riverina Division of New South Wales has been known for many years. Seismic refraction tests were carried out on a number of sections to assist in the interpretation of the gravity results during July and Sepetember, 1949.