From 1 - 10 / 589
  • The Gawler craton in South Australia hosts the Olympic Dam Cu-U-Au deposit, the world's preeminent iron oxide copper-gold (IOCG) deposit and largest uranium resource. With a total resource now standing at 7.7 billion tonnes, Olympic Dam is also one of the world's largest copper and gold deposits (BHP Billiton, 2007 Annual Report). The emergence of IOCG deposits as a recognized mineral deposit class (Hitzman et al., 1992) has been followed by increasing interest in these deposits from explorers and researchers. IOCG deposits are attractive exploration targets because of their favorable grade-tonnage characteristics, credits of gold and other metals (e.g., U, Ag), and physical characteristics that are particularly amenable to geophysical exploration techniques. Despite this growing interest and an increasing number of published descriptions of the major deposits, there have been few multidisciplinary integrated studies of the regional geologic settings and metallogeny of major IOCG provinces globally. As one of the world's key IOCG provinces, the Gawler craton has experienced rapid growth in exploration expenditure this decade, resulting in discoveries of the Prominent Hill IOCG deposit in 2001 and the Carrapateena deposit in 2005 (Fig. 1Go). Over the period of these discoveries in the eastern Gawler craton, explorers in the central Gawler craton were defining a number of new gold ...

  • This map shows the area of the Automatic Longline 183m and 700m Depth Closure within the Commonwealth Scalefish Hook Sector. It was produced for the Australian Fisheries Management Authority.

  • Package holding all available processed data and well completion reports relevant to the Ashmore-Londonderry 2007Acreage Release in workstation format - Geoframe, Kingdom and Landmark.

  • The Tarcoola goldfield in central South Australia is hosted by the Paleoproterozoic Paxton Granite and Tarcoola Formation metasedimentary rocks. Both of these units are intruded by narrow dikes of the Lady Jane Diorite, which is considered to be part of the Gawler Range-Hiltaba volcano-plutonic event. Crosscutting relationships and 40Ar/39Ar dating of alteration sericite and primary hornblende have demonstrated that veining, alteration, and mineralization occurred synchronously with intrusion of the diorite dikes at ~1580 Ma. Mineralization at the Perseverance deposit in the Tarcoola goldfield is hosted by quartz veins in both granite and the lower parts of the Tarcoola Formation. Alteration intensity and mineralization are related to fracture density. Very high gold grades (up to 270 ppm) are recorded in carbonaceous siltstones of the Tarcoola Formation. Primary fluid inclusions from mineralized quartz veins at Perseverance are dominated by two-phase aqueous inclusions and three-phase H2O-CO2(l)-CO2(v) ± CH4 inclusions. Both inclusion types have salinities of <10 wt percent NaCl equiv, with evidence of other salts being present. Both types homogenize between 150° and ~340°C. They occur together in single quartz grains, which suggests the coexistence of aqueous and carbonic fluids. At the Perseverance deposit the maximum depth of fluid inclusion formation is estimated as 10 km. Processes resulting from pressure fluctuations during brittle fracturing causing phase separation are suggested to be the dominant gold precipitation mechanism, although definitive fluid inclusion evidence for either phase separation or fluid mixing is lacking. Wall-rock sulfidation may have also contributed to gold deposition. Pb isotope compositions of galena from gold-bearing mineralized veins at Perseverance are similar to K-feldspar and whole-rock samples of the Paxton Granite. This is consistent with a common source of Pb and possibly other ore components for both the granite and galena, but not all potential reservoirs were tested. Variably altered and gold mineralized samples that had Paxton Granite precursors show a loss of Nd and a trend from {varepsilon}Nd(1580Ma) values of about -6.2 in slightly altered samples toward more positive {varepsilon}Nd values of about -3.3 in high-grade gold samples. Of the local lithologic units, the Lady Jane Diorite has {varepsilon}Nd(1580Ma) values of about +0.1 and is the most probable source of the more primitive Nd isotope components in mineralized samples. Mineralization in the Tarcoola goldfield has similarities to both orogenic and intrusion-related gold styles. The demonstrated coeval timing of diorite dikes and mineralization at Tarcoola, together with the Nd isotope constraints on metal sources, and the presence of similar mafic dikes in several other known gold prospects in the central Gawler gold province, suggests that the diorite was an essential part of the gold mineralization event throughout this province.

  • Package holding all available processed data and well completion reports relevant to the Troubadour-Money Shoal 2007Acreage Release in workstation format - Geoframe, Kingdom and Landmark.

  • This presentation was delivered at the Geothermal Energy Industry Roundtable at Parliament House in March 2007.

  • National Geochemical Survey of Australia field training for the geoscience agencies of all States and the Northern Territory took place during 2007 and early 2008. The knowledge transfer mechanisms comprise a detailed National Geochemical Survey of Australia: Field Manual (GA Record 2007/08), this training presentation and several days of in-field sample collection under the guidance of NGSA staff.

  • Presented to the Association of Mining and Exploration Companies (AMEC), Perth, March 2007

  • Methodology for bushfire mapping using the ACRES Landsat archive

  • Situated just inboard of the late Neoproterozoic Australian rift margin (Tasman Line), the Mount Isa region occupies a critical position in reconstructions of Rodinia, combining an older crystalline basement (Kalkadoon-Leichhardt Block) affected by the 1850 Ma Palaeoproterozoic Barramundi orogeny with three variably deformed and vertically stacked supracrustal sequences ranging in age from 1790-1595 Ma (Leichhardt, Calvert and Isa superbasins). Orogenesis in these three superbasins peaked around 1585Ma (Isa orogeny) and obscures an earlier history of syn-extensional magmatism, deformation and low-pressure/high-temperature metamorphism linked to basin formation and normal faulting at higher crustal levels. Basin geometry and normal fault patterns indicate a change in the direction of extension from east-west to ENE-WSW at Calvert time and a corresponding shift in the depositional environment from narrow intracontinental rift to passive continental margin by 1685 Ma. Coincidently, fluviatile to near-shore sedimentary facies (Haslingden Group and Surprise Creek Formation in the west) gave way to deep water marine sediments, including turbidites (Soldiers Cap Group in the east), and basaltic magmas evolved from continental to oceanic tholeiites in composition as the crust became increasingly attenuated. This pattern of basin formation and near continuous extension is also evident in the 1720-1640 Ma Willyama Supergroup at Broken Hill but is difficult to reconcile with existing reconstructions of Rodinia in which the Broken Hill and Mount Isa terranes are juxtaposed against rocks of similar age in southwest Laurentia that preserve a record of contractional deformation related to plate convergence, terrane accretion and collision. Equally difficult to reconcile are palaeogeographic reconstructions of Australia which place the Broken Hill and Mount Isa terranes adjacent to each other in a back-arc position while maintaining an along-strike continuity with the rocks of southwest Laurentia (Mojave, Yavapai and Mazatzal Provinces). An alternative reconstruction of Proterozoic eastern Australia is proposed in which back-arc extension in the Broken Hill and Mount Isa terranes was linked to retreat of a west-dipping (present-day coordinates) subduction zone and associated magmatic arc that now resides partially or wholly within North America. Eastern Australia and Laurentia ceased to be part of a single continental landmass soon after 1800 Ma and thereafter followed increasingly divergent tectonic paths until re-amalgamated during collision at ca. 1600 Ma. Extension in the Broken Hill and Mount Isa terranes produced a North American Basin and Range-style crustal architecture that has no obvious counterpart in southwest Laurentia.