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  • Contents: 1.Black LP, Blake DH, Olatunji JA. Ages of granites and associated mineralisation in the Herberton tinfield of northeast Queensland. 2.Simpson CJ. LANDSAT: developing techniques and applications in mineral and petroleum exploration. 3.Pinchin J. A seismic investigation of the eastern margin of the Galilee Basin, Queensland. 4.Collins CDN. Crustal structure of the central Bowen Basin, Queensland. 5.Shafik S. A new nannofossil zone based on the Santonian Gingin Chalk, Perth Basin, Western Australia. 6.Black LP, Gulson BL. The age of the Mud Tank Carbonatite, Strangways Range, Northern Territory. 7.Green DC, Hulston JR, Crick IH. Stable isotope and chemical studies of volcanic exhalations and thermal waters, Rabaul caldera, New Britain, Papua New Guinea. 8.Sydenham PH. Early geophysical practice - the BMR instrument collection. 9.Smith EL. Storage and retrieval systems for the Reference Minerals Collection and the Georgina Basin Project (BMR). 10.Riesz EJ. Can rank-size 'laws' be used for undiscovered petroleum and mineral assessments. 11.Seventh BMR Symposium.

  • Like other areas throughout the north of the Northern Territory, Groote Eylandt is dominated by a landscape of great age. Previous interpretations have argued that this landscape experienced repeated cycles of uplift and erosion during the Tertiary. This view is challenged by the evidence of two palaeovalleys which traverse the island ; both are filled with Cretaceous sedimentary rocks and are incised into a plateau surface of supposedly Miocene age. The Cretaceous marine transgression was the most important event in the long-term landscape history of Groote Eylandt. The resulting raised base-level, and the associated sedimentary infilling of valleys, lifted streams from their existing valleys, and promoted the development of a new stream network, which has persisted till the present. Apart from the obvious drainage alterations, no other significant modifications to the Groote Eylandt landscape have occurred since at least the late Mesozoic: an escarpment traversing the island has retreated less than 500 m since this time, and the upland plateau and surrounding lowland plains of pre-Cretaceous age have maintained their general form.

  • Increasingly precise stratigraphic resolution by biostratigraphy, isotope stratigraphy, and sequence analysis in the Neoproterozoic allows more convincing palaeogeographic reconstructions than hitherto possible, so that the original connections amongst structural basins can be demonstrated. The Neoproterozoic stratigraphy of Australia can now be analysed in terms of four supersequences, with finer subdivision possible in the Ediacarian or Terminal Proterozoic. The palaeogeography of Australia during eight time intervals within the Neoproterozoic is assessed, with varying degrees of confidence. Our interpretation follows previous models of the Adelaide Rift Complex as a Neoproterozoic intracratonic rift between the Gawler and Curnamona cratons. The rift is at a high angle to the associated east-west elongated epicratonic sag of the Centralian Superbasin. In the earliest Cambrian the Flinders zone of the Adelaide Rift Complex was transformed to a failed arm or aulacogen by continental breakup along its southern part. Sedimentation ceased before the Late Cambrian-Early Ordovician (500 Ma) Delamerian Orogeny. The Rift Complex underwent two phases of onlap (= extension) accompanied by the deposition of (Sturtian and Marinoan) glacials. A third phase of onlap represented by the Billy Springs Formation occurred during right-lateral shearing (Petermann Ranges orogeny) that caused thrusting and the emergence of the east-west oriented Musgrave Block in the middle of the Superbasin. The Superbasin was finally dismembered by the rise of the southern Arunta Block between the Amadeus and Ngalia structural basins during the mid-Carboniferous Alice Springs Orogeny. According to the SWEAT hypothesis, Australia was joined in the Neoproterozoic with India, Antarctica, and Laurentia, so that the Tasman Line faced the Canadian-Wyoming cordilleran line. The configuration of the north-south trending Adelaide Rift Complex and the east-west trending Centralian Superbasin was mirrored by the basins in Laurentia to form a T, which split at the end of the Neoproterozoic by growth of a precursor of the Pacific Ocean.

  • Granitic rocks in different terranes and of different ages in the Prince Charles Mountains (PCM) show systematic compositional differences. Archaean granitic basement rocks of the southern PCM have compositions unlike those of typical Archaean tonalite- tronhjemite-granodiorite (TTG) terranes and consist mainly of within-plate types, which probably post-date crust formation and early metamorphic events. Unusually HFSE-rich (Zr, Nb, and Y) hornblende-biotite granite gneiss with A-type (anorogenic) affinities was probably derived by fractionation of mafic magma, but other granites represent intracrustal melts. Orthopyroxene-bearing tonalitic to granitic orthogneiss of the c. 1000 Ma high-grade terrane in the northern PCM and adjacent areas includes a large proportion of Y-depleted, Sr-undepleted volcanic arc granitoids, probably derived by melting of a plagioclase-poor mafic source (e.g. amphibolite or eclogite) in a Palaeo- or Mesoproterozoic Andean-type plate margin. Tonalite-granodiorite and mafic to felsic metavolcanic rocks at Fisher Massif also formed in an active continental margin, with an associated island arc, about 1300 million years ago. Most c. 1000 Ma granitoids also have volcanic arc characteristics, but there are significant syn-collision and within-plate types, indicating a polygenetic origin in a high-grade terrane formed at a convergent plate margin. Syn to late-metamorphic orthopyroxene granitoids (charnockites) include HFSE-rich quartz monzonitic varieties, which probably formed by fractionation of mantle-derived magma, and more siliceous granites, which represent high-temperature, predominantly intracrustal melts of dry granulite-facies orthogneiss. These granites are mainly Y-depleted, implying high-pressure melting with residual garnet in crust thickened by continental collision (between Archaean cratons in India and Antarctica) and heated by magmatic underplating. Major Cambrian plutons have A-type features, consistent with melting of dry granulite-facies rocks caused by mafic underplating. Emplacement near the present Lambert Glacier graben suggests an association with internal fracturing that preceded eventual break-up of Gondwana.

  • Five new Carboniferous to Permian palynological Oppel-zones have been identified through detailed analyses of core samples taken from the Joe Joe Group sediments of the Galilee Basin. In ascending stratigraphic order, and in relation to their host formations , the Oppel-zones are: the Verrucosisporites basiliscutis Oppel-zone (A), spanning the Lake Galilee Sandstone and the basal Jericho Formation; the Brevitriletes leptoacaina Oppel-zone (B), in the mid-Jericho Formation ; the Diatomozonotriletes birkheadensis Oppel-zone (C), in the upper Jericho Formation; the Asperispora reticulatispinosus Oppel-zone (D), encompassing much of the Jochmus Formation and the uppermost part of Jericho Formation (including the Oakleigh Siltstone Member); and the Microbaculispora tentula Oppel-zone (E), in the upper part of the Jochmus Formation. The three oldest Oppel-zones are grouped to form the Carboniferous (Namurian A-upper Westphalian D) Spelaeotriletes queenslandensis Superzone, which correlates with the Spelaeotriletes ybertii Assemblage of earlier workers. The overlying Asperispora reticulatispinosus Oppel-zone (D) (upper Westphalian D-Upper Autunian, or early Asselian) mostly correlates with the Potonieisporites Assemblage. The uppermost Microbaculispora tentula Oppel-zone (E), late Autunian (late Carboniferous) to early Tastubian (Early Permian), correlates with the Upper Stage 2. Application of the Oppel-zones has clarified relationships between outcrop sections of the earlier defined Joe Joe Formation of the Galilee Basin and lithological units subsequently identified in the sub-surface. Stratigraphic interpretation of the Oppel-zones with their lithostratigraphic equivalents suggests that late Palaeozoic glaciation began in the Westphalian D and continued until the late Asselian/earliest Tastubian, when climatic warming resulted in sea level rise associated with continental glacial melting. The palynological record shows the impact of this glacial episode, which caused significant global compositional changes in palynofloras in the Late Carboniferous/Early Permian. These changes may allow correlations between Gondwana and Laurasia. Eleven new species of miospore are described.

  • Hydrothermal mineral deposits are the products of crustal geochemical processes that extract metals from source regions and concentrate them at depositional sites. These processes and the regions in which they occur constitute mineral systems. Processes that occur within source regions define the characteristics (e.g. temperature, pressure, pH, salinity, redox, sulphur content) of hydrothermal fluids, which, in turn, determine the metal carrying capacity of the fluid. Mineral deposits that contain Cu, Zn, Pb, Ag and/or Au can be classified into three general groupings based on metal assemblages: (1) Zn-Pb-Ag±Au , (2) Cu±Au , and (3) Au±Ag. These groupings are predicted from fluid characteristics and the solubility of metals in the fluids. The hydrothermal geochemistry of Sn, W, U and Mo is not considered in this discussion. Mineral deposit diversity results from the complex interplay of processes in source regions and depositional sites. First-order processes that occur in source regions include devolatilisation and degassing, circulation of surficial fluids, and expulsion of connate fluids. These and second-order processes such as SO2 disproportionation result in hydrothermal fluids with diverse temperatures, acidities, salinities, redox conditions, and, hence, metal-carrying capacities. Many of the processes in the source region are directly or indirectly linked to geological characteristics of the source region, such as granitoid type and basinal lithology. Three first-order depositional processes cause metal deposition: phase separation, reaction with host rocks , and mixing with ambient fluids. The efficiency of metal deposition depends critically on the steepness of chemical gradients in the depositional environment. The interplay of source and depositional processes produces the observed diversity of mineral deposits, and placing these processes in a mineral system framework provides a powerful tool for understanding and, potentially, for discovering mineral deposits.

  • This paper presents a brief overview of the Mount Isa copper deposit as a type example of a group of rare but high-grade deposits, whose formation appears to be linked to regional metamorphism

  • The enigmatic conodont Clavohamulus primitus Miller is described from the Tremadocian part of the Ninmaroo Formation, Georgina Basin. This key subzone species for North American sequences in Oklahoma, Texas and Utah has been discovered in two samples, one from Western Queensland and the other from the Northern Territory. The discovery enables a firmer correlation of the Lower Tremadocian part of the Georgina sequence with sequences in North America. The microstructure of C. primitus is discussed and illustrated.

  • Dune soils in a longitudinal dune-swale landscape in the Kulwin Dunefield, east of the Darling River, in New South Wales, are classified as Xeric Haplargids in fine-loamy, siliceous, thermic families (siliceous sands Uc 1.23). They are paralleled in swales by fine, mixed thermic Xeric Hapl argids (solonised brown soils Uc 1.12. The very fine sands are mostly quartz. Weatherable minerals make up <10 g/kg. Clays have cation-exchange capacities at pH 7.0 of about 50-60 cmol (+)/kg and clay mica in amounts of about 150 g/kg. Textural differences in the two soils are in large part explained by differences in their aeolian parent materials. The dune sands are probably locally derived, whilst the fine material making up the swales is parna, of both local and regional origin. The winnowing action of eastwardmoving, converging helicoidal winds produces sandy dunes, while the parna is moved on. At the same time, the wind brings in more fines (in suspension) and coarse particles (by saltation), depositing them in both the dunes and swales. Some of the coarser dune material may have been eroded by runoff and deposited in the swales. The dune-swale landscape is believed to have been formed at about 16-20 ka. The profile characteristics indicate that a common palaeosol exists below depths of about 195-200 cm in the dune profile and 40 cm in the swale profile. A calcic horizon with up to 23 per cent carbonate has formed in the swale soil below a depth of 40 cm. In the dune, the ground soi l has only traces of carbonate, but the upper part of the palaeosol apparently has been enriched with carbonate from the dune. Silt and fine sand size clay bodies (parna) occur in the Bt1 horizon of the swale soil and throughout the Bt horizons of the dune ground soil. In the Bt1 horizon of the swale soil, insepic- skelsepic fabric occurs. lIIuviation argillans occur in voids and channels in the swale soil argillic horizon and on sands. In both the swale and the dune ground soils, illuviation argillans also bridge between sand grains. Pedogenic leaching of carbonate, pedoplasmation, and clay translocation thus have taken place in the soils during and since deposition of the parna. Because of the parna and salt additions (such as CaC03), the soils have adequate physical and chemical properties to be productive in the climate in which they occur.

  • Early Archaean ( >3 b.y. old) metapelites from the Napier Complex of East Antarctica are enriched in MgO and depleted in K2O and Rb compared with late Archaean and Proterozoic metapelites, probably reflecting a higher proportion of mafic to ultramafic material and sodic (tonalitic to granodioritic) felsic igneous rocks in the source. A number of the more magnesian are strongly depleted in Cr, Ni, Cu, and V, and may have been formed by metamorphism of sediments derived from hydrothermally altered mafic or ultramafic igneous rocks. There is evidence for metamorphic depletion of Rb relative to K in these high-temperature granulite facies metapelites, many of which have high K/Rb ratios, and for depletion of U relative to Th in granulite-facies metapelites compared with those of amphibolite facies. The unique occurrence, on a regional scale, of assemblages containing sapphirine + quartz, and osumilite in metapelites of the Napier Complex may be due to their unusual chemical compositions, as well as to exceptionally high temperatures of metamorphism (900-950°C). Such assemblages are found only in the more magnesian rocks (mostly with mg > 0.6) in the Napier Complex, whereas younger metapelites are, with few exceptions, relatively iron-rich. Nevertheless, regional high-grade metamorphism with geothermal gradients sufficiently steep to allow formation of these rare assemblages is likely to have been confined to the Archaean.