A methodology to estimate renewal time scales in estuaries: the Tagus Estuary case   总被引：2，自引：0，他引：2  

Frank?BraunschweigEmail author  Flávio?Martins  Paulo?Chambel  Ramiro?Neves 《Ocean Dynamics》2003,53(3):137-145

High-resolution hydrodynamic models are a common tool to simulate water dynamics in estuaries. Results from these models are, however, difficult to interpret without the aid of additional parameters to integrate the information. In this paper a methodology to understand the transport patterns in the Tagus Estuary is proposed. It is based on the computation of two renewal time scales: residence time and integrated water fraction. This last parameter is used to build a dependency matrix that gives the integrated influence of each region of the estuary at a selected point. The parameters are computed using a Lagrangian transport model coupled to the hydrodynamic model. Results show that Tagus Estuary has two different types of regions: the central part of the estuary, with low renewal efficiency, and three regions with higher renewal efficiency. Renewal mechanisms are, however, different for each region as shown by the dependency matrix. Comparison of renewal time scales with results from a water-quality model revealed that residence time is not a limiting parameter for primary production in the Tagus Estuary.Responsible Editor: Hans Burchard  相似文献   

Mineral-scale Sr-isotope constraints on magma evolution and chamber dynamics in the Rum layered intrusion,Scotland   总被引：1，自引：0，他引：1  

Frank?J.?TepleyIIIEmail author  Jon?P.?Davidson 《Contributions to Mineralogy and Petrology》2003,145(5):628-641

Sr isotopic zoning within single plagioclase crystals from rocks from Unit 9 of the Rum layered intrusion is used to infer events during crystal growth in a magma undergoing contamination. The ⁸⁷Sr/⁸⁶Sr diversity among minerals and between cores and rims of plagioclase crystals increases as the boundary between unit 9 and the overlying Unit 10 peridotite is approached. Models of near-solidus interaction of the cumulate with a fluid or melt, or large scale textural re-equilibration, cannot easily account for the systematic differences in ⁸⁷Sr/⁸⁶Sr between small crystals and the rims of larger crystals.We propose a simple interpretation in which crystal growth is concentrated along the cool margins of the reservoir. Crystals are subsequently advected to a site of accumulation at the base of the reservoir, probably by episodic plume-like dense downwellings allowing mixing of isotopically zoned and unzoned crystals.If the core-rim isotope variations are inherited from primary magmatic growth, then the small distances over which they are now preserved (1–2 mm) place constraints on the minimum cooling rate of the intrusion. Although the length scale of diffusive equilibration is influenced by a number of poorly-constrained variables (starting temperature, feldspar composition, temperature-time path) cooling was clearly very rapid with cooling to effective closure (~1,000 °C) within a few thousand years.Editorial responsibility: I. Parsons  相似文献   

Adakite-like signature of Late Miocene intrusions at the Los Pelambres giant porphyry copper deposit in the Andes of central Chile: metallogenic implications   总被引：7，自引：0，他引：7  

Martin?Reich  Miguel?A.?ParadaEmail author  Carlos?Palacios  Andreas?Dietrich  Frank?Schultz  Bernd?Lehmann 《Mineralium Deposita》2003,38(7):876-885

Adakite-like features are recognized in the Late Miocene (~10 Ma) porphyritic intrusions of the Los Pelambres giant porphyry copper deposit, central Chile (32°S). Located within the southern portion of the flat-slab segment (28–33°S) of the Chilean Andes, the Al- and Na-rich porphyries of Los Pelambres display distinctly higher Sr/Y (~100–300) and La_N/Yb_N (~25–60) ratios than contemporaneous and barren magmatic units (e.g., La Gloria pluton, Cerro Aconcagua volcanic rocks) of the same Andean magmatic belt. Strong fractionation of heavy rare earth elements (HREE), absence of Eu anomalies, high Sr/Y and Zr/Sm and low Nb/Ta ratios suggest melt extraction from a garnet-amphibolite source. The Late-Miocene adakite-like porphyritic intrusions at Los Pelambres formed closely related in time and space to the subduction of the Juan Fernández Ridge (JFR) hotspot chain along the Chilean margin. Current tectonic reconstructions reveal that, at the time of formation of the Los Pelambres rocks, a W-E segment of the JFR started to subduct beneath them, producing a slow-down of a previously rapid southward migration of a NE-ridge—trench collision. These particular tectonic conditions are favorable for the origin of the Los Pelambres porphyry suite by melting of subducting young hotspot rocks under flat-slab conditions. The incorporation of crustal components into the oceanic lithopheric magma source by subduction erosion is evidenced by the Sr-Nd isotope composition of the Los Pelambres rocks different from the MORB signatures of true adakites. A close relationship apparently exists between the origin of this adakite-like magmatism and the source of the mineralization in the Los Pelambres porphyry copper deposit.Editorial handling: R.J. Goldfarb  相似文献   

Regional-scale hydrothermal alteration in the Central Blake River Group,western Abitibi subprovince,Canada: implications for VMS prospectivity   总被引：1，自引：0，他引：1  

Mark?D.?HanningtonEmail author  Frank?Santaguida  Ingrid?M.?Kjarsgaard  Larry?M.?Cathles 《Mineralium Deposita》2003,38(4):393-422

The Late Archean Blake River Group is a thick succession of predominantly mafic volcanic rocks within the southern zone of the Abitibi greenstone belt. It contains a number of silicic volcanic centers of different size, including the large Noranda volcanic complex, which is host to 17 past-producing volcanogenic massive sulfide deposits. The Noranda complex consists of a 7- to 9-km-thick succession of bimodal mafic and felsic volcanic rocks erupted during five major cycles of volcanism. Massive sulfide formation coincided with a period of intense magmatic activity (cycle III) and the formation of the Noranda cauldron. Hydrothermal alteration in these rocks is interpreted to reflect large-scale hydrothermal fluid flow associated with rapid crustal extension and rifting of the volcanic complex. The alteration includes abundant albite, chlorite, epidote and quartz (silicification), which exhibit broad stratigraphic and structural control and correlate with previously mapped whole-rock oxygen isotope zonation. The Mine Sequence volcanic rocks are characterized by abundant iron-rich chlorite (Fe/Fe+Mg >0.5), hydrothermal amphibole (ferroactinolite) and coarse-grained epidote of clinozoisite composition (<10 wt% Fe ₂O ₃). Volcanic rocks of the pre-cauldron sequences, which contain only subeconomic stringer mineralization, are characterized by less abundant chlorite and mainly fine-grained epidote (>10 wt% Fe ₂O ₃) lacking the clinozoisite solid solution. Alteration in the Mine Sequence volcanic rocks persists along strike well beyond the limits of the main ore deposits (as far as several tens of kilometers) and can be readily distinguished from greenschist facies metamorphic assemblages at a regional scale. The lack of similar alteration in the pre-cauldron sequences is consistent with limited ¹⁸O-depletion and suggests that the early history of the volcanic complex did not support large-scale, high-temperature fluid flow in these rocks. Comparisons with a much smaller, barren volcanic complex in nearby Ben Nevis township reveal important differences in the alteration mineralogy between volcanoes of different size, with implications for area selection during regional-scale mineral exploration. The Ben Nevis Complex consists of a 3- to 4-km-thick succession of mafic, intermediate and felsic volcanic rocks centered on a small subvolcanic intrusion. Alteration of the volcanic rocks comprises mainly low-temperature assemblages of prehnite, pumpellyite, magnesium-rich chlorite (Fe/Fe+Mg <0.5), iron-rich epidote (>10 wt% Fe ₂O ₃) and calcite. Actinolite ± magnetite alteration occurs proximal to the intrusive core of the complex, but the limited extent of this alteration indicates only local high-temperature fluid circulation adjacent to the intrusion. A distal zone of carbonate alteration is located 4–6 km from the center of the volcano. Although iron-bearing carbonates are present locally within this zone, the absence of siderite argues against a high-temperature origin for this alteration. These observations do not offer positive encouragement for the existence of a fossil geothermal system of sufficient size or intensity to have produced a large massive sulfide deposit.  相似文献   

Tectonic and sedimentary basin evolution of the eastern Bangong–Nujiang zone (Tibet): a Reading cycle     

Werner?Schneider  Frank?MatternEmail author  PuJun?Wang  Cai?Li 《International Journal of Earth Sciences》2003,92(2):228-254

The ophiolite-bearing Bangong-Nujiang zone (BNZ) traversing central Tibet from east to west separates the Qiangtang block in the north from the Lhasa block in the south. Their stratigraphic development indicates that both blocks once formed a continuous continental platform until the Late Triassic. Following Late Paleozoic-Triassic rifting, ocean crust formed between both blocks during the Late Triassic creating the Dongqiao-Naqu basin (DNB) among other basins (Yu et al. 1991). The analysis of the rift flank sequences reveals that rifting was dominated by transtension. The basin was shortened by post-Mid-Cretaceous transpression. Thus, the overall basin evolution represents a Reading cycle despite some active margin processes which gave this cycle a special imprint. Major basin parts were preserved despite transpressional shortening suggesting that the eastern BNZ represents a remnant basin. Our understanding of the DNB solves the prior problem of viewing the BNZ as a Mid-Late Jurassic collisional suture although typical collision-related deformation, thickening, mountain building, as well as related molasse formation are lacking. Our model also explains the scattered linear ophiolite distribution by local transpression of remnant oceanic basin floor without having to consider problematic long range ophiolite thrusting.  相似文献   

A review of mortality maps included in the annual reports on vital statistics for Ireland, 1864-1998     

Houghton F 《Irish geography : bulletin of the Geographical Society of Ireland》2002,35(2):213-215

Since 1864, some 135 reports have been produced examining marriages, birth and deaths for Ireland. The reports produced during the period prior to World War I are notable for the maps and charts that are included and the level of detail provided. Recent reports have failed to include mortality maps, while those produced since 1950 generally show a declining level of detail.  相似文献   

Chemical Mechanism Development: Laboratory Studies and Model Applications     

Harald Geiger  Ian Barnes  Karl H. Becker  Birger Bohn  Theo Brauers  Birgit Donner  Hans-Peter Dorn  Manfred Elend  Carlos M. Freitas Dinis  Dirk Grossmann  Heinz Hass  Holger Hein  Axel Hoffmann  Lars Hoppe  Frank Hülsemann  Dieter Kley  Björn Klotz  Hans G. Libuda  Tobias Maurer  Djuro Mihelcic  Geert K. Moortgat  Romeo Olariu  Peter Neeb  Dirk Poppe  Lars Ruppert  Claudia G. Sauer  Oleg Shestakov  Holger Somnitz  William R. Stockwell  Lars P. Thüner  Andreas Wahner  Peter Wiesen  Friedhelm Zabel  Reinhard Zellner  Cornelius Zetzsch 《Journal of Atmospheric Chemistry》2002,42(1):323-357

Within the German Tropospheric Research Programme (TFS) numerous kinetic and mechanistic studies on the tropospheric reaction/degradation of the following reactants were carried out: oxygenated VOC, aromatic VOC, biogenic VOC, short-lived intermediates, such as alkoxy and alkylperoxy radicals.At the conception of the projects these selected groups were classes of VOC or intermediates for which the atmospheric oxidation mechanisms were either poorly characterised or totally unknown. The motivation for these studies was the attainment of significant improvements in our understanding of the atmospheric chemical oxidation processes of these compounds, particularly with respect to their involvement in photooxidant formation in the troposphere. In the present paper the types of experimental investigations performed and the results obtained within the various projects are briefly summarised. The major achievements are highlighted and discussed in terms of their contribution to improving our understanding of the chemical processes controlling photosmog formation in the troposphere.  相似文献   

Analyses of organic and inorganic contaminants in Salton Sea fish   总被引：3，自引：0，他引：3  

Riedel R  Schlenk D  Frank D  Costa-Pierce B 《Marine pollution bulletin》2002,44(5):403-411

Chemical contamination of fish from the Salton Sea, a quasi-marine lake in Southern California, could adversely impact millions of birds using the Pacific Flyway and thousands of humans using the lake for recreation. Bairdiella icistia (bairdiella), Cynoscion xanthulus (orangemouth corvina), and Oreochromis spp. (tilapia) were sampled from two river mouths and two nearshore areas of the Salton Sea. Muscle tissues were analyzed for a complete suite of 14 trace metals and 53 pesticides. Fish muscle tissues had concentrations of selenium ranging between 1.89 and 2.73 microg/g wet weight. 4,4'-DDE accounted for 94% of the total DDT metabolites. Total DDTs ranged between 17.1 and 239.0 and total PCBs between 2.5 and 18.6 ng/g wet weight. PCB congeners 132, 138, 153, 168, and 180 comprised over 50% of the total PCBs. Given the potential implementation of a commercial fishing at the Salton Sea in the future, the presence of persistent organic pollutants and selenium warrants further research into the effects of these mixtures on fish populations, and on wildlife and humans consuming fish.  相似文献   

An empirical garnet (YAG) – xenotime thermometer     

Joseph M. Pyle  Frank S. Spear 《Contributions to Mineralogy and Petrology》2000,138(1):51-58

 A pronounced negative correlation between the yttrium concentration in garnet ([Y]_Grt) and temperature has been observed in xenotime (YPO₄)-bearing metapelites from central New England, USA. The [Y]_Grt decreases roughly two orders of magnitude (∼5500 to less than 100 ppm Y) over a 150 °C interval. A regression of ln([Y]_Grt) against estimated reciprocal temperature yields the following relationship: with R² = 0.97. The decrease in garnet Y content is most rapid over garnet- to staurolite-zone conditions (450–550 °C) and the thermometer has a precision of a few degrees in this range. Received: 21 January 1999 / Accepted: 13 September 1999  相似文献   

The Equation of State of Lakes     

Frank J Millero 《Aquatic Geochemistry》2000,6(1):1-17

In recent years, a number of workers have studied the stability of deep lakes such as Lake Tanganyika, Lake Baikal and Lake Malawi. In this paper, the methods that can be used to determine the effect that the components of lakes have on the equation of state are examined. The PVT properties of Lakes have been determined by using apparent molal volume data for the major ionic components of the lake. The estimated PVT properties (densities, expansibility and compressibilities) of the lakes are found to be in good agreement with the PVT properties (P) of seawater diluted to the same salinity. This is similar to earlier work that showed that the PVT properties of rivers and estuarine waters could also be estimated from the properties of seawater.The measured densities of Lake Tanganyika were found to be in good agreement (± 2 × 10^-6 g cm^-3) with the values estimated from partial molal properties and the values of seawater at the same total salinity (S_T = 0.568). The increase in the densities of Lake Tanganyika waters increased due to changes in the composition of the waters. The measured increase in the measured density (45 × 10^-6 g cm^-3) is in good agreement (46 × 10^-6 g cm^-3) with the values calculated for the increase in Na⁺, HCO₃ ^-, Mg²⁺, Ca²⁺ and Si(OH)₄.Methods are described that can be used to determine the conductivity salinity of lakes using the equations developed for seawater. By combining these relationships with apparent molal volume data, one can relate the PVT properties of the lake to those of seawater.  相似文献