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.

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.

Considerable exploration interest has been generated by the platinum-group-element (PGE) and Ni-Cu potential of the Archean layered mafic-ultramafic intrusions in the west Pilbara Craton, Western Australia. The Munni Munni Intrusion contains the largest known resource of PGEs associated with a layered intrusion in Australia, and the Radio Hill and Mount Sholl intrusions host significant resources of Ni-Cu-Co sulfides. Titaniferous magnetite layers, remobilized sulfides, and structurally controlled hydrothermal polymetallic deposits have also been a focus for exploration in recent years. The ca. 2.9 Ga Munni Munni, Andover, Radio Hill, Mount Sholl, and Sherlock layered intrusions are a cogenetic suite of high-level (<5 kb) bodies that represent some of the oldest mineralizing systems of their type in the world. Although they display similar field relationships and mineralogical, geochemical, and isotopic features, their contrasting chalcophile metal distribution patterns show that the timing and mechanism of the S-saturation event were critical for the development of PGE-enriched sulfide-bearing layers and basal segregations of base-metal sulfides. The intrusions form thick (>5.5 km) 'dike'-like bodies or relatively thin (0.5-2 km) sheets and sills emplaced at different levels along major lithological discontinuities in the upper crust. Rhythmically layered ultramafic components are generally thinner than, and occur along the northern sides of, more massive overlying mafic components. The ultramafic zones consist of dunite, lherzolite, wehrlite, olivine websterite, clinopyroxenite, and websterite. Inverted pigeonite gabbronorite, magnetite gabbro, olivine gabbro, anorthositic gabbro, and anorthosite comprise the mafic sequences. Olivine and clinopyroxene were generally the first minerals to crystallize, except in the Andover Intrusion, where orthopyroxene preceded clinopyroxene and possibly reflects greater contamination of the parent magma by felsic crustal material. The crystallization of chromite was inhibited in the ultramafic zones by the partitioning of Cr into early crystallizing clinopyroxene, thus downgrading the potential for PGE-chromite associations. The PGE mineralization in the Munni Munni Intrusion occurs in the upper levels of a porphyritic plagioclase websterite orthocumulate layer directly below the ultramafic-gabbroic zone contact. Mineral compositional trends and Nd isotopic data indicate that a Pd-Pt-Au-enriched S-undersaturated magnesian basaltic magma was frequently injected into a small magma chamber during formation of the ultramafic zone. A major influx of more fractionated, S-saturated tholeiitic gabbroic magma related to the resident magnesian magma, rapidly inflated the chamber and induced turbulent magma mixing that resulted in the formation of the PGE-bearing porphyritic websterite layer. In contrast, the parent magmas that formed the Mount Sholl, Radio Hill, Andover, and Maitland intrusions were saturated in S before they were emplaced into the magma chambers. In these intrusions gravitational and structural controls were important for the concentration of PGE-poor (5-400 ppb Pt + Pd + Au) massive sulfides in depressions and structural embayments along the basal contacts beneath the thickest sequences of mafic-ultramafic cumulates. The parent magmas to the west Pilbara intrusions were siliceous high-Mg basalts of Al-depleted komatiitic affinity (Barberton-type) with 9-12% MgO, 15-25 ppm Sc, 12-18 ppm Y, low Al2O3/TiO2 (ca. 11, or half chondrite ratios), and light-rare earth enrichment (chondrite-normalized La/Sm = 2.7, La/Lu = 9.0). They were generated with garnet in the residual asthenospheric mantle with probable involvement of a pre-3.0 Ga subduction-modified lithospheric mantle. Isotopic and geochemical modelling suggests that the magmas were contaminated by ca. 3.0-3.3 Ga Archean tonalitic to granodioritic crust before being emplaced into high-level magma chambers.