The Aitik Cu–Au–Ag deposit in northern Sweden: a product of high salinity fluids     

Christina Wanhainen  Curt Broman  Olof Martinsson 《Mineralium Deposita》2003,38(6):715-726

The Aitik Cu–Au–Ag deposit is located in northern Sweden and is hosted by strongly deformed 1.9 Ga Svecofennian volcano-sedimentary rocks. The main copper mineralization, which occurs as disseminations and veinlets, is hosted by garnet–biotite schist. Subeconomic mineralization in the footwall to the ore is hosted by feldspar–biotite–amphibole gneiss and porphyritic quartz monzodiorite. The deposit has been affected by post-mineralization metamorphic and igneous activity. Fluid inclusions in six samples of copper-mineralized quartz veins record the presence of three different fluid populations. The main ore was deposited from an aqueous, highly saline (31–37 eq. wt% NaCl + CaCl₂) fluid. This fluid was trapped in inclusions intimately associated with the main chalcopyrite mineralization. Later bornite deposition took place from a less saline (18–27 eq. wt% NaCl + CaCl₂), aqueous fluid. A third fluid composed of almost pure CO₂, interacted with the copper-rich system during a post-ore event. The Aitik Cu–Au–Ag deposit shares some features with both porphyry-type and Fe-oxide–Cu–Au deposits. A high calcium content of the ore fluids, similar to other Cu–Au deposits in northern Scandinavia, suggests a contribution to the salinity of the mainly magmatic-hydrothermal fluids from evaporitic rocks in stratigraphically lower units.  相似文献   

Rescaling the Region: The integration of Hawkes Bay food and forestry industries into East Asia     

Christina A. Stringer 《The Australian geographer》2002,33(1):63-77

This paper explores the changing relationship of a region (Hawkes Bay, New Zealand), its industries and enterprises to Asia-Pacific industrial complexes. Land-based industries in Hawkes Bay provide examples of new connections and local adaptations of production to emerging agro-food and forestry complexes, centred upon East Asia. Integration into these complexes, which has only been possible in the context of the gradual relaxation of regulatory regimes that has occurred over the past two decades, has facilitated access to new markets. In some cases, integration is an outcome of East Asian ownership of New Zealand-based nodes along the commodity chain. In others, it is an outcome of New Zealand actors producing to meet 'site of consumption' demand. The paper concludes that new dynamics in the spheres of trade, production and investment are instituted by and feed into new geographic links and interactions, referred to in the paper as a rescaling of the region.  相似文献   

Wave observations from an array of directional buoys over the southern Brazilian coast     

Henrique Patricio Prado Pereira  Nelson Violante-Carvalho  Izabel Christina Martins Nogueira  Alexander Babanin  Qingxiang Liu  Uggo Ferreira de Pinho  Fabio Nascimento  Carlos Eduardo Parente 《Ocean Dynamics》2017,67(12):1577-1591

It is well known that the majority of buoy measurements are located around the US coast and along some Europeans countries. The lack of long-term and densely spaced in situ measurements in the Southern Hemisphere in general, and the South Atlantic in particular, hinders several investigations due to the lack of detailed metocean information. Here, we present an effort to overcome this limitation, with a dense network of buoys along the Brazilian coast, equipped with several meteorological and oceanographic sensors. Out of ten currently operational buoys, three are employed to present the main characteristics of waves in the Southern part of the network. For the first time, sensor characteristics and settings are described, as well as the methods applied to the raw wave data. Statistics and distributions of wave parameters, swell propagating events, comparison with a numerical model and altimeters and a discussion about the occurrence of freak waves are presented.  相似文献   

Local and Target Exploration of Conglomerate-Hosted Gold Deposits Using Machine Learning Algorithms: A Case Study of the Witwatersrand Gold Ores,South Africa     

Nwaila  Glen T.  Zhang  Steven E.  Frimmel  Hartwig E.  Manzi  Musa S. D.  Dohm  Christina  Durrheim  Raymond J.  Burnett  Mark  Tolmay  Leon 《Natural Resources Research》2020,29(1):135-159

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Advancements in web‐mapping tools for land use and marine spatial planning     

Ainhoa Gonzlez  Christina Kelly  Anna Rymszewicz 《Transactions in GIS》2020,24(2):253-267

Land use and marine spatial planning processes are increasingly supported by systematic assessment techniques, particularly by multi‐criteria spatial analysis methods. This has been facilitated by the growing release and uptake of web‐mapping tools, which contribute to transparent, consistent, and informed planning processes and decisions. This article reviews the usability, functionality, and applicability of contemporary planning web‐mapping tools to identify the state‐of‐the‐art and future prospects. The review reveals that interfaces are increasingly available and intuitively applicable by non‐specialized users. Basic map navigation and data querying functionality is being expanded to incorporate advanced map‐making and online data geoprocessing capabilities that enable deriving new data and insights. However, the majority of published planning web tools are one‐off solutions, and a disconnect between research and practice is rendering many of these inaccessible or obsolete. Despite the significant progress made in advancing their provision in the last decade, there is a need for developing transferable interfaces that are maintained beyond project end dates, for them to effectively and consistently support planning processes.  相似文献   

Zonal versus meridional velocity variance in satellite observations and realistic and idealized ocean circulation models     

Robert B. Scott  Brian K. Arbic  Christina L. Holland  Ayon Sen  Bo Qiu 《Ocean Modelling》2008,23(3-4):102-112

Global, high-quality, satellite-based observation of oceanic currents over the past 13 years has revealed ubiquitous quasi-horizontal eddies in the mesoscale (tens to hundreds of kilometers), confirming the view of a highly turbulent ocean suggested by observational programs in the 1970s. Idealized quasigeostrophic turbulence models suggest mesoscale turbulent flow can vary between isotropic, and highly anisotropic zonal jets. Here we compare the zonal and meridional velocity variance from satellite altimetry. We find that, for an unexplained reason and despite the chaotic nature of turbulence, the surface flow is organized into mesoscale patches where either zonal or meridional velocity variance dominates. The patches persist over 13 years, much longer than the turbulent timescale of a few months. Implications include potentially highly anisotropic redistribution of tracers by the mesoscale flow. Zonally averaged velocity variances reveal a slight preference for meridional over zonal velocity variance. Realistic primitive equation models succeed in reproducing both the patchy structure in local preference for either zonal or meridional velocity variance, and the zonally averaged preference for meridional variance. Idealized models of fully developed, quasigeostrophic turbulence fail in both regards.  相似文献   

Modelling the photopolarimetric variability of AA Tau     

Mark O'Sullivan  Michael Truss  Christina Walker  Kenneth Wood  Owen Matthews  Barbara Whitney  J. E. Bjorkman 《Monthly notices of the Royal Astronomical Society》2005,358(2):632-640

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Adequacy of satellite derived rainfall data for stream flow modeling   总被引：2，自引：0，他引：2  

Guleid Artan  Hussein Gadain  Jodie L. Smith  Kwabena Asante  Christina J. Bandaragoda  James P. Verdin 《Natural Hazards》2007,43(2):167-185

Floods are the most common and widespread climate-related hazard on Earth. Flood forecasting can reduce the death toll associated with floods. Satellites offer effective and economical means for calculating areal rainfall estimates in sparsely gauged regions. However, satellite-based rainfall estimates have had limited use in flood forecasting and hydrologic stream flow modeling because the rainfall estimates were considered to be unreliable. In this study we present the calibration and validation results from a spatially distributed hydrologic model driven by daily satellite-based estimates of rainfall for sub-basins of the Nile and Mekong Rivers. The results demonstrate the usefulness of remotely sensed precipitation data for hydrologic modeling when the hydrologic model is calibrated with such data. However, the remotely sensed rainfall estimates cannot be used confidently with hydrologic models that are calibrated with rain gauge measured rainfall, unless the model is recalibrated. G. Artan, J. L. Smith and K. Asante – work performed under USGS contract 03CRCN0001.  相似文献   

Intercomparison and validation of snow albedo parameterization schemes in climate models   总被引：1，自引：0，他引：1  

Christina A. Pedersen  Jan-Gunnar Winther 《Climate Dynamics》2005,25(4):351-362

Snow albedo is known to be crucial for heat exchange at high latitudes and high altitudes, and is also an important parameter in General Circulation Models (GCMs) because of its strong positive feedback properties. In this study, seven GCM snow albedo schemes and a multiple linear regression model were intercompared and validated against 59 years of in situ data from Svalbard, the French Alps and six stations in the former Soviet Union. For each site, the significant meteorological parameters for modeling the snow albedo were identified by constructing the 95% confidence intervals. The significant parameters were found to be: temperature, snow depth, positive degree day and a dummy of snow depth, and the multiple linear regression model was constructed to include these. Overall, the intercomparison showed that the modeled snow albedo varied more than the observed albedo for all models, and that the albedo was often underestimated. In addition, for several of the models, the snow albedo decreased at a faster rate or by a greater magnitude during the winter snow metamorphosis than the observed albedo. Both the temperature dependent schemes and the prognostic schemes showed shortcomings.  相似文献   

Three-dimensional elastic scattering by near-surface heterogeneities     

Christina D. Riyanti  Gérard C. Herman 《Geophysical Journal International》2005,160(2):609-620

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