No abstract available

No abstract available

Poorly exposed Paleoproterozoic sandstones and siltstones of the Killi Killi Formation record developement of a large turbidite complex. Killi Killi Formation sediments were eroded from the uplifted ~1860 Ma Nimbuwah and Hooper Orogens as indicated by detrital zircons with sediment deposition at ~1840 Ma. Facies analysis, isopach maps and detrital zircon populations, combined with Sm-Nd data from the Tanami region and Halls Creek Orogen, confirm the previously suggested correlation of the Paleoproterozoic successions in the Eastern zone of the Halls Creek Orogen and the Tanami region. Detrital zircons from the Aileron Province suggest the turbidite complex extends into the Arunta region, however, high metamorphic grade precludes direct facies comparisons in the Arunta region. Portions of the turbidite complex in the Tanami region are dominated by mudstones, consisting of low-density turbidites and associated hemipelagites, that potentially acted as a redox boundary to gold-bearing fluid. Gold prospectivity in turbiditic systems is increased within these mudstone sequences with the potential for further gold discoveries.

Report summarises results from the Offshore and Onshore Energy Security Progams undertaken between 2006 and 2011.

A number of Paleoproterozoic layered mafic-ultramafic intrusions in the central part of the Halls Creek Orogen of East Kimberley, Western Australia, have been explored for platinum-group elements (PGE), chromium, nickel, copper, cobalt and gold. Here we report on the halogen geochemistry of apatite and biotite in a number of these intrusions. Interstitial apatite is ubiquitous in these intrusions and, in most samples, tends to be relatively enriched in F- and OH-endmembers and relatively poor in Cl (< 20 mole %). Fluorapatite occurs in the more evolved igneous rocks and in marginal samples that apparently have been contaminated by metamorphic country rock. Cl/F ratios generally increase with bulk rock molar Mg/(Mg + Fe) ratios, as observed in other intrusions. Only a few samples show Cl-enrichment as high as that seen in the Stillwater and Bushveld complexes beneath the major stratabound PGE deposits. The most Cl-rich compositions observed occur in the upper part of the Springvale intrusion, where it is associated with troctolite, and in a single sample from the McIntosh intrusion. For the former intrusion, it is suggested that volatiles migrating out of the lower part of the mafic stratigraphy stabilized olivine at the expense of pyroxene. Associated biotite tends to be low in both Cl and F, containing no more than 10 mole % of these components. It is concluded that the East Kimberley intrusions contained a low to moderate volatile component that, during the combined processes of crystallization, degassing and fractionation of interstitial halogen-bearing minerals, was able to produce a late, mobile interstitial silicate liquid or volatile-rich fluid phase of variable Cl/F content that gave rise to most of the observed variations within any given intrusion. The exceptions include some marginal samples that appear to have been affected by country rocks, either during emplacement (assimilation) or during later metamorphism. The generally low Cl/F ratio of apatite, the lack of primary amphibole and the high background sulfur concentrations of the East Kimberley intrusions suggest that these magmas were relatively dry. The possible development of high-grade, PGE-enriched horizons by late-stage hydrothermal processes that could have mobilized significant amounts of the PGE and sulfur is considered to be of low potential.

Assessment of geological, geochemical and isotopic data indicate that a subgroup of volcanic-hosted massive sulphide (VHMS) deposits has a major magmatic-hydrothermal source of ore fluids and metals. This group, which is characterised by high Cu and Au grades, is distinguished by aluminous advanced argillic alteration assemblages or metamorphosed equivalents. These characteristics are interpreted as the consequence of disproportionation of magmatic SO2. Other than deposits associated with advanced argillic alteration assemblages, the only deposit for which we ascribe a major magmatic-hydrothermal contribution is the Devonian Neves Corvo deposit. This deposit differs from other deposits in the Iberian Pyrite Belt and around the world in being extremely Sn-rich, Comparison with 'normal' VHMS deposits suggest that these subgroups of VHMS deposits may form in specialised tectonic environments. The Cu-Au-rich deposits appear to form adjacent to magmatic arcs, an environment conducive to the generation of hydrous, oxidised melts by melting metasomatised mantle in the wedge above the subducting slab. This contrasts with the back-arc setting of 'normal' VHMS deposits in which relatively dry granites formed by decompression melting drive seawater-dominated hydrothermal circulation. The tectonic setting of highly Sn-rich VHMS deposits such as Neves Corvo is less clear, however thick continental crust below the ore-hosting basin may be critical as it is in other Sn deposits.

Abstract to be published as part of Seismix Conference Proceedings in a GA Record

Fluids in mineral systems may be derived from above, within, or below the Earth's crust. Fluid production rates and observed Cl contents indicate that the dominant inputs to mineral systems are surface derived (meteoric & bittern) waters and those transported into the crust from below, principally by magmas. These conclusions can be used as part of any analysis of the distribution of mineral systems and ore deposits.

Presented at the Evolution and metallogenesis of the North Australian Craton Conference, 20-22 June 2006, Alice Springs. The Tennant Creek goldfield, the third largest goldfield in the Northern Territory, producing over 150 tonnes of gold (Wedekind et al., 1989), was only discovered in the mid-1930s due to the association of gold with ironstone rather than quartz veins. Over the last two decades ironstone-hosted gold deposits have been included in the group of deposits termed iron-oxide copper-gold (IOCG) deposits (Hitzman et al., 1992). Elsewhere in the Northern Territory, prospects with IOCG characteristics have been recognised in the southeastern Arunta (Hussey et al., 2005), and potential for these deposits has been recognised in the Mount Webb area of the Warumpi Province (Wyborn et al., 1998). <p>Related product:<a href="https://www.ga.gov.au/products/servlet/controller?event=GEOCAT_DETAILS&amp;catno=64764">Evolution and metallogenesis of the North Australian Craton Conference Abstracts</p>

The North Pilbara Terrane has the largest variety of mineral deposits of any Archaean province. It contains the oldest known examples of volcanic-hosted massive sulphide (VHMS), lode Au, porphyry Cu, orthomagmatic Ni-Cu-PGE-V, pegmatitic Ta-Sn and epithermal deposits, with a diversity more characteristic of Phanerozoic mobile belts. Despite this diversity the North Pilbara Terrane appears to lack any major mineral deposits, with the exception of the Wodgina Ta-Sn pegmatite field. Below, we present the metallogenic history of the North Pilbara Terrane in the context of its tectonic development and then compare it to other Archaean provinces to assess controls on metal endowment.