澳大利亚稀土矿床主要类型及其成矿特征

澳大利亚稀土矿资源丰富,类型多样。通过对澳大利亚170余处稀土矿床地质特征的总结,将澳大利亚稀土矿床划分为4个主要类型和13个亚类。主要类型为与岩浆活动有关的稀土矿床、与沉积盆地有关的稀土矿床、与近代河流和滨海砂矿有关的稀土矿床和与表生风化作用有关的稀土矿床,并对每个亚类型矿床的分布特征、成矿时代和地质特征进行了总结。在此基础上,根据澳大利亚稀土矿床的地质背景、成矿特征等因素,初步划分出9个主要的稀土矿床矿集区,并从商业价值和资源潜力角度分别对矿集区的找矿潜力进行分析,综合认为H和E区是下一步进行矿业投资的良好对象。     

Assessment of recharge to groundwater systems in the arid southwestern part of Northern Territory, Australia, using chlorine-36

 The sustainability of community water supplies drawn from shallow aquifers in the arid southwest of the Northern Territory has been evaluated using the radioactive isotope chlorine-36 (³⁶Cl). These aquifers include fractured sandstones of the Ngalia Basin, fractured metamorphic rocks and Cainozoic sands and gravels. ³⁶Cl/Cl ratios for these shallow, regional groundwaters exhibit a bimodal distribution with peaks at 205 (±7) and 170 (±7)×10^–15. The higher ratio probably represents modern (Holocene) recharge, diluted with windblown salts from local playa lakes, and occurs mostly around the margin of the basin. The lower ratio corresponds to a ³⁶Cl "age", or mean residence time, of 80–100 ka, implying that the last major recharge occurred during the last interglacial interval (Oxygen Isotope Stage 5). These values are mainly observed in the interior of the Ngalia Basin. Lower values of the ³⁶Cl/Cl ratio measured near playa lakes are affected by addition of chloride from remobilised salts. Finite carbon-14 (¹⁴C) data for the groundwaters are at variance with the ³⁶Cl results, but a depth profile suggests low recharge, allowing diffusion of recent atmospheric carbon to the water table. The ³⁶Cl results have important implications for groundwater management in this region, with substantial recharge only occurring during favourable, wet, interglacial climatic regimes; most community water supplies are dependent on these "old" waters. Received, September 1997 · Revised, August 1998, March 1999 · Accepted, March 1999     

P-T-X conditions of hydrothermal fluids and precipitation mechanism of stibnite-gold mineralization at the Wiluna lode-gold deposits,Western Australia: conventional and infrared microthermometric constraints

The Wiluna lode-gold deposits are located in the Archean Wiluna greenstone belt, in the northern sector of the Norseman-Wiluna belt in the Yilgarn Craton of Western Australia. They are hosted in subgreenschist facies meta-basalts, and controlled by the Wiluna strike-slip fault system and associated shear veins and breccias. The 13 individual lode-gold deposits have produced around 115 t Au from 1901 to 1946 and 1986 to today. Historically, they also produced 38.3 t As and 3.5 t Sb. Gold formed in two stages: stage 1 gold-pyrite-arsenopyrite is finely disseminated in the wallrock and breccia fragments, whereas stage 2 gold-stibnite is located in massive shear veins and breccia matrix, as fracture-fill and in banded-colloform textured veins. Stibnite-gold orebodies only occur in some of the deposits (e.g., Moonlight and northern part of the West Lode) and also display a restricted vertical extent, being preserved only in the uppermost 200 m of stibnite-bearing lodes.Petrographic, conventional, and infrared microthermometric and laser-Raman analysis on stibnite-bearing quartz veins and breccias reveal that the antimony- and gold-rich hydrothermal fluid was of mixed H₂O-NaCl-CO₂±CH₄ type. Microthermometric measurements reveal maximum homogenization temperatures of 340 °C (average 290±25 °C), and a wide range of salinities between 0.2 and 23 eq. wt% NaCl. Aqueous-carbonic fluid inclusions contain variable X_CO2+CH4 (0.03 to 0.82), with the carbonic phase containing a maximum X_CH4 of 0.21.Combined petrographic and microthermometric evidence suggests that the fluid inclusion properties reflect fluid immiscibility of a low-salinity, medium X_CO2+CH4, homogeneous parent fluid at about 290 °C and pressures between 700 and 1,700 bar. Fluid immiscibility was triggered by cyclic pressure release during fault-zone movement. The decompression (adiabatic cooling) of the hydrothermal fluids shifted the ore fluid to lower temperatures, significantly reduced the degree of stibnite undersaturation, and caused stibnite to precipitate. The deposition of stibnite reduced the ore-fluid H₂S concentration, thereby destabilized gold bisulfide complexes in solution, and caused gold precipitation locally. This mechanism explains the intimate spatial association of stibnite and gold in quartz veins and breccias in the stibnite-gold orebodies at Wiluna.Editorial handling: B. Lehmann     

The geomorphic character and hydrological function of an upland swamp,Budderoo plateau,southern highlands,NSW, Australia

Upland swamps are a form of topogenous mire that occur on the plateau areas of eastern Australia. These systems are well recognized for their ecological value, but little is known about their internal hydrological function and how this relates to their geomorphic structure and evolution. In this study, the geomorphic, sedimentological, and hydrological properties of an intact upland swamp on the Budderoo Plateau NSW are investigated. The geomorphic structure of the swamp is simple, and the sedimentology comprises basal layers of coarse sands, overlain by several layers of organic accumulation up to 3.3?m in thickness. Each of these sedimentary units has different hydrological behaviors (rates of water throughflow and discharge) that drive the overall function of the swamp in response to rainfall of various magnitudes and duration. Four hydrological response types have been identified in the functioning of this swamp. These response types (RT) are characterized by different peaks and recession responses to rainfall. The form of the hydrograph produced is controlled by antecedent water table position and the amount, timing and duration of rainfall. Depending on antecedent moisture conditions, the swamp can operate either as a store for water or as a rapid conduit for water throughflow and overland flow.     

Impact cratering and distal ejecta: the Australian record

The Australian continent has one of the best-preserved impact-cratering records on Earth, closely rivalling that of North America and parts of northern Europe, and the rate of new discoveries remains high. In this review 26 impact sites are described, including five small meteorite craters or crater fields associated with actual meteorite fragments (Boxhole, Dalgaranga, Henbury, Veevers, Wolfe Creek) and 21 variably eroded or buried impact structures (Acraman, Amelia Creek, Connolly Basin, Foelsche, Glikson, Goat Paddock, Gosses Bluff, Goyder, Kelly West, Lawn Hill, Liverpool, Matt Wilson, Mt Toondina, Piccaninny, Shoemaker, Spider, Strangways, Tookoonooka, Woodleigh, Yallalie, Yarrabubba). In addition a number of possible impact structures have been proposed and a short list of 22 is detailed herein. The Australian cratering record is anomalously biased towards old structures, and includes the Earth's best record of Proterozoic impact sites. This is likely to be a direct result of aspects of the continent's unique geological evolution. The Australian impact record also includes distal ejecta in the form of two tektite strewn fields (Australasian strewn field, ‘high-soda’ tektites), a single report of 12.1?–?4.6 Ma microtektites, ejecta from the ca 580 Ma Acraman impact structure, and a number of Archaean to Early Palaeoproterozoic impact spherule layers. Possible impact related layers near the Eocene?–?Oligocene and the Permian?–?Triassic boundaries have been described in the literature, but remain unconfirmed. The global K?–?T boundary impact horizon has not been recognised onshore in Australia but is present in nearby deep-sea cores.     

Environmental quality indicators: where to from here?

Environmental or land quality indicators are being developed internationally as a means whereby the ‘State of the Environment’ (SoE) can be assessed and trends monitored. In Australia, the use of indicators in SoE reporting is in its early stages of development. Indicators have been developed, in relation to agriculture, for flora and fauna, soil, chemical contamination, surface waters and groundwater. Internationally, the World Bank has listed ‘indicators of pressure’ on the land, ‘indicators of state and impact’, and ‘indicators of response’ for each of seven major issues of land degradation. Late in 1996, an ‘indicators of catchment health’ workshop in Australia identified a relatively small number of key indicators relating to farm productivity, soil health, water quality and ‘landscape integrity’, later adding social indicators, and also distinguishing between indicators at farm and catchment scales. A broad range of other indicators was also considered by various participants in the workshop, which concluded by supporting a nationally co‐ordinated effort and the establishment of a national steering committee. Although most indicators are static measures, those from which predictions can be made require a greater emphasis on the functioning of the system. This implies that indicators are only one aspect of system modelling, and that environmental or land assessment needs to progress further than the search for quality indicators. Since this involves both biophysical and human processes, geographers should be playing a central role.     

South Australian earthquakes, 1980–92

The seismicity of South Australia over the period 1980–92 is presented as a follow‐up to earlier studies. The South Australian seismic network has undergone a significant expansion in the last decade, and with it an increase in the number and precision of located earthquakes. The distribution of recent seismic activity is similar to the historical pattern of earthquakes and the previous instrumental seismicity maps, all of which show the three main areas as being the Flinders‐Mt Lofty Ranges, Eyre Peninsula, and the southeast. The one notable exception in the recent study is the presence of earthquake activity in the Musgrave Block, a previously aseismic region. Intensity characteristics are reported for earthquakes that were sufficiently widely felt. Fault plane solutions for three Flinders Ranges earthquakes (previously unpublished) are also presented; the focal mechanisms are consistent with predominant northeast‐southwest compression. The seismic moment method was used to estimate the seismic risk for the major population centres in terms of probability of exceedance of seismic intensity within a given period. These estimates are based on the recurrence parameters and intensity attenuation function for the region. The results place Adelaide close to the AS2121 ‐ 1979 Earthquake Code Zone I/Zone 2 boundary.     

Estimating impacts of changed land use on recharge: review of modelling and other approaches appropriate for management of dryland salinity

To manage dryland salinity, one needs to know how changed land use affects groundwater recharge. Few techniques are available for comparing 'deep drainage' under different land uses. Soil-tracer methods, although good for replication and remote field sites, are subject to spatial variability. Lysimeters are good for comparisons but are difficult for drier areas and sloping land. Agronomic water-balance studies, where appropriate soil-water measurements exist, may be used with a soil-vegetation model to estimate long-term deep drainage. Complex models are required to analyze specific land-use differences, such as perenniality and root and leaf area dynamics, but models require intensive and extensive data for calibration. This approach is time-consuming, labour-intensive, and difficult in remote locations. Because of the one-dimensionality of most soil-vegetation models and the small fraction of the total water balance that is deep drainage, little success has occurred in extrapolating beyond the research plot, or to spatially heterogeneous systems such as alley farming. Some 'top-down' modelling and landscape disaggregation approaches have been partially successful in making catchment or regional-scale predictions. The direction for further work depends on the level of recharge reduction that is required for most groundwater systems and difficulties that it imposes. Electronic Publication     

昆士兰州土地产权信息服务系统建设及启示

介绍了澳大利亚昆士兰州自然资源和水资源部产权登记系统和智慧图管理信息系统建设历程、系统功能及应用情况,对GIS信息系统的建设方法进行了有益的探讨与研究。     

Flower viewing from horseback? New directions in Chinese tourism in Australia

ABSTRACT

In this century Chinese tourists in Australia have rapidly become the most numerous national source. Relatively little is known about their socio-economic status, their geographical origins and expectations of tourism, and their attitudes to and perceptions of Australia, although every Australian state has devised a specific Chinese tourism strategy to tap into this market. Chinese tourism is concentrated in metropolitan areas in the eastern states, has evolved from group tours to individual plans, and is relatively high spending. Unless geographical and tourism research on Chinese tourism aligns with contemporary theoretical developments in tourism studies, the type of knowledge being produced will be limited. Whilst there is value in extending existing knowledge, important social insights into the Chinese tourists’ experience of Australia will not emerge. Although Chinese tourism is similar to earlier waves from East Asia, it constitutes a distinct component of the contemporary Australian market. A deeper understanding of this phenomenon requires the adoption of practice theories that privilege social practices as the entry point for theorising and conducting research. In advocating such an approach, we highlight challenges of linguistic and cultural differences, scale and governmentality in providing a qualitative research agenda for geographical and tourism studies’ engagements with Chinese tourism.