Legacy product - no abstract available

In 2007, three seismic lines were collected by Geoscience Australia and the Geological Survey of Queensland from Cloncurry to south of Charters Towers via Croydon and Georgetown, and a fourth line by AuScope to the northeast of Mt Surprise. Signals were recorded to ~20 seconds two-way travel time (TWT), which equates to about 60 kilometres in depth. The recent lines are among the latest in a series of deep seismic profiles conducted across Queensland since 1980.

The NNW-trending tectonic grain of the Eastern Yilgarn Craton (EYC) was established as a result of predominantly ENE-directed extension (D1 and D3) and E(ENE)-W(WSW) (D2, D4) to NE-SW directed (D5) contraction. The result has been a succession of NNW-striking co-planar, but temporally discrete, fabric elements that can be difficult to reliably interpret at any single location. Despite this, many past workers interpreted the NNW-striking fabric as the result of only one deformation event, and used it as a marker for correlating structural events across the region. In order to unravel the complexity, this paper presents a new six-fold (D1 to D6) deformation nomenclature based on >10000 new mesoscale structural observations including their kinematic analysis and cross cutting relationships. These mesoscale data were referenced with regional 3D map patterns, stratigraphic-magmatic-metallogenic considerations, and deep seismic reflection images. This integrated geodynamic-architectural approach is applicable to solving structural-event histories in other coplanar poly-deformed terrains. Gold mineralisation occurred during the first five events, but was particularly vigorous from D3 onwards. The D3 event marked the most profound change in the tectonic evolution of the EYC, with changes in greenstones, granites and tectonic mode (lithospheric extension and core complexes), with the first significant gold deposited within extensional shear zones that dissected the crust. Later contraction (D4) was imposed at a high angle to the previously established anisotropic architecture. The outcome was the creation of a new dynamic permeability framework which resulted in gold mineralisation during NNW-striking sinistral strike-slip faulting and associated thrusting. A further stress switch (D5) further modified the architecture resulting in N- to NNE-striking dextral strike-slip faulting, and the final period of gold mineralisation before late-stage extension (D6).

No abstract available

The Eastern Goldfields Province (EGP) is a late Archaean orogenic belt located on the eastern margin of the Yilgarn Craton. The EGP is characterised by a prominent NNW-trending tectonic grain developed largely during regional ~E-W oriented shortening. A simplistic sequence of largely progressive compressional deformation events (D1 to D4+) has been used by previous workers to explain the development of the EGP. Regional `D2? was thought to be responsible for most of the finite strain, and therefore a reliable marker event for correlating deformation histories across the region. A re-examination of the deformation history has shown that `D2? (Kalgoorlie Orogen of Weinberg et al., 2003) was not a single progressive event. Rather, it was episodic and involved several stages of switching of the tectonic mode (compression-extension switching) between ~2665 Ma and ~2655 Ma. The sequence of events during `D2? was an early stage of ~E-W shortening (D2a), followed by extension with basin formation and normal fault movement (D2E), and finally a second stage of ~E-W compression (D2b). We introduce this sequence of events as the Wangkathaa Orogeny, more complex in tectonics and broader in geographical scope than the Kalgoorlie Orogen. Features of the Wangkathaa Orogeny are well illustrated by the geometry and geological relationships that occur in the Kurnalpi Terrane (Welcome Well area) and the Kalgoorlie Terrane (Ora Banda, Kambalda, and the Boorara Domains) of the central and southern EGP. Available geochronology indicates that this sequence of events was likely to have been diachronous across the entire EGP and the eastern Southern Cross Province (of the Yilgarn Craton). Recognition of these separate (episodic) stages of ~E-W oriented compression and extension is important in our understanding the tectonic evolution of the EGP. Switching tectonic mode between compression and extension will change the state of mean-stress in a rock mass (e.g., from net dilation to net constriction and vice versa), and is an effective method in transporting and trapping mineral-rich fluids. The paradox of the different timings established for `D2? across the province are explained by the Wangkathaa Orogeny, especially if it were diachronous, as different workers dated different phases of an episodic orogeny.

Early formed rift architecture has a major control on the subsequent compressional and strike-slip fault systems that host the world class St Ives Goldfield in the Yilgarn Craton, Western Australia. The current topography of the faults, at both a camp and regional scale, is a reflection of the geometry of the early rifts and old basement boundaries. Early structures have been physically mapped and identified in potential field data sets, isopach thickness variations and by the distribution of dolerite and basalt units. The early rift geometry is interpreted to have been a series of early WNW-trending normal faults and breached relay ramps associated with oblique rifting along an older NNW-trending basement boundary. Strike changes on major regional faults, such as the Boulder-Lefroy Fault, correlate with the location of major early formed WNW-trending faults. These control dilational and contractional fault segments associated with several world class gold fields. Within the St Ives Goldfield a series of N-trending linking thrusts developed during D2 inversion that are bounded by WNW-trending faults. During gold mineralization these linking thrusts became contractional jogs that now host several gold ore bodies. The WNW-trending relay faults acted as transfer faults syn-gold mineralization, although only discrete segments of these transfer faults were active during gold mineralization. They transferred strain from a complex combination of block on block movement associated with thrusting and strike-slip movement on NW- and N-trending faults. The WNW-trending faults were also a focus of intrusive dykes and larger scale intrusions that are inferred to have produced the pronounced WNW-trending gravity trends in regional potential field data sets.

Legacy product - no abstract available

The primary objective of AGSO Survey 116 was the acquisition of high-quality deepseismic data and other geophysical data over the Indonesian - Australian JointDevelopment Zone (JDZ) and adjacent areas of the Timor Sea. The cruise was partof a program being undertaken by AGSO, to determine the structural architecture ofthe north western margin of Australia and the influence of structuring on the location,migration and trapping of hydrocarbons in the region. The survey vessel R.V. Rig Seismic left Darwin on 22 January 1993 but returned toport on 30 January due to equipment problems and poor weather conditions. Theship again departed Darwin on 3 February and began seismic acquisition on 5February. The survey was completed on 7 March and finished in Darwin on 8 March. During the survey, 16 seismic lines were completed for a total of 3595 km at anaverage of 119 km per day. All of the proposed Timor Sea Tie lines were completed,however lines across Zone of Cooperation C of the JDZ and the Timor Trough inIndonesian waters were not collected because an agreement between AGSO andIndonesian authorities had not been finalised. In addition to the proposed program,the survey included 5 lines of the Malita Graben program, totalling 1028 km. TheseN-S lines were shot when marginal weather conditions prevented seismic acquisitionin an E-W direction. The Timor Sea Tie lines were tied to 17 exploration wells. Acquisition within the Joint Development Zone was undertaken on behalf of NOPEC,who have been authorised by the Joint Development Authority to research this area.All seismic lines were collected to specifications agreed upon by NOPEC and AGSO. The seismic data were recorded from a 4800 m streamer, configured with 192 x 25 mactive groups. The record length was 16 seconds, and the sample interval 2 ms.The seismic source consisted of dual sleeve gun arrays with a capacity of 50 litres.Navigation for the survey was provided by differential Global Positioning System(dGPS), using shore reference stations Darwin and Broome. The seismic acquisition system was inoperable during the first week at sea duringwhich time weather conditions also prevented acquisition. After repairs to thesystem, both the seismic and non-seismic acquisition systems ran without majorproblems. Navigational data were of good quality, with differential GPS beingavailable at least 95% of the survey time.

The North West Margin Transects Cruise is part of a program being undertaken by AGSO to determine the structural architecture of the north-western margin of Australia and the influence of structuring on the location, migration and trapping ofhydrocarbons in the region. An important aspect of this program is the acquisition ofa series of full margin 'dip' transects extending from unrifted cratonic basement tobeyond the continent-ocean boundary, and at least two 'strike' transects that willextend along the full length of the shelf from the eastern Timor Sea to North WestCape. The major objective of the proposed cruise is to extend previous AGSO deepseismic surveys across the Browse (Survey 119), offshore Canning (SNOWS-3/Survey 120) and northern Carnarvon Basins (SNOWS-/Survey 101, SNOWS-2/Survey 110) to complete these margin transects. Specific objectives of theproposed survey are: *Determine the regional structural framework of the Scott Plateau area and itsrelationship to adjacent features such as the Argo Abyssal Plain, the BrowseBasin and the Rowley Sub-Basin of the offshore Canning Basin; *Determine the regional structural framework of the Exmouth Plateau and itsrelationship to adjacent features such as the Barrow-Dampier Sub-basin, and theArgo and Gascoyne Abyssal Plains. *Define the broad deep-crustal structure of the region and develop a modelexplaining the tectonic, subsidence and thermal history of the Scott Plateau andthe Exmouth Plateau in relation to the development of the continental margin andadjacent ocean basins. *Assess the effects of the deep crustal structures and their reactivation phases onthe development of known petroleum accumulations. To address these objectives it is proposed that RV Rig Seismic be used to acquireabout 3276 km of deep crustal (16 second record length) multichannel seismic andother geophysical data along 9 transects across the outer margins of the Browse,offshore Canning and northern Carnarvon Basins. The survey will tie into the 1991SNOWS-1 (101), 1992 SNOWS-2 (110), 1993 Browse Basin (119) and SNOWS-3(120) surveys.

PROJECT BACKGROUND The Sedimentary Basins of Eastern Australia (SBEA) Project is a multidisciplinary study of the Bowen, Surat and Gunnedah Basins. It is part of the National GeoscienceMapping Accord and is a collaborative project between the Australian Geological Survey Organisation (AGSO, formerly the Bureau of Mineral Resources, BMR),Geological Survey of Queensland (Department of Minerals and Energy) and New South Wales Department of Mineral Resources (Geological Survey and Coal & Petroleum Geology branches), with cooperation from CSIRO, universities and industry. The Bowen, Surat and Gunnedah Basins have considerable resource potential and,although there have been regional studies of the basins in the past, there are still uncertainties as to their precise geometry, mode of formation, the response of thebasin to tectonic events in the adjacent orogens, and the control exerted by these events on the timing and generation of hydrocarbons. OBJECTIVES The aim of the project is to undertake an integrated basin analysis with emphasis onthe tectonic, structural, sedimentary and thermal histories of the basins in order to assess their economic potential for hydrocarbons. This Record describes the interim products of the second phase of a regional seismic synthesis, and focuses on theapplication of the principles of sequence stratigraphy in the interpretation and integration of industry and BMR seismic data in the Bowen and Surat Basins,Queensland, between 23°30'S and 26°S (Fig. 1). It also includes examples of isopach and structure contour maps, in reduced format, based on this phase of interpretation, and briefly outlines the methods and techniques used to produce these maps. Themaps are available through the AGSO Sales Centre, and digital data from the PetroseisTM System Software are available in various file formats.