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Recharge estimation for transient ground water modeling 总被引：11，自引：0，他引：11
Reliable ground water models require both an accurate physical representation of the system and appropriate boundary conditions. While physical attributes are generally considered static, boundary conditions, such as ground water recharge rates, can be highly variable in both space and time. A practical methodology incorporating the hydrologic model HELP3 in conjunction with a geographic information system was developed to generate a physically based and highly detailed recharge boundary condition for ground water modeling. The approach uses daily precipitation and temperature records in addition to land use/land cover and soils data. The importance of the method in transient ground water modeling is demonstrated by applying it to a MODFLOW modeling study in New Jersey. In addition to improved model calibration, the results from the study clearly indicate the importance of using a physically based and highly detailed recharge boundary condition in ground water quality modeling, where the detailed knowledge of the evolution of the ground water flowpaths is imperative. The simulated water table is within 0.5 m of the observed values using the method, while the water levels can differ by as much as 2 m using uniform recharge conditions. The results also show that the combination of temperature and precipitation plays an important role in the amount and timing of recharge in cooler climates. A sensitivity analysis further reveals that increasing the leaf area index, the evaporative zone depth, or the curve number in the model will result in decreased recharge rates over time, with the curve number having the greatest impact. 相似文献
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宁芜盆地火山-次火山岩的锆石U-Pb年龄、Hf同位素组成及其地质意义 总被引：40，自引：23，他引：17
宁芜火山盆地是长江中下游重要的火山盆地之一,在盆地内自下而上依次发育龙王山组、大王山组、姑山组和娘娘山组火山岩和若干个同源次火山岩或小侵入岩体。本文对宁芜盆地火山-次火山岩进行了详细的锆石U-Pb年龄和Hf同位素地球化学研究。研究结果表明,大王山组粗安岩锆石U-Pb年龄为130.3±0.9Ma,姑山组两个粗安岩锆石U-Pb年龄分别为128.2±1.3Ma和128.5±1.8Ma,另外三个侵入岩年龄分别为127.1±1.2Ma、128.3±0.6Ma和128.2±1.0Ma,均为早白垩纪。综合前人成果,认为长江中下游地区火山盆地内火山活动的时限在135～124Ma之间,不存在侏罗纪岩浆活动。宁芜盆地火山岩和侵入岩的锆石176Hf/177Hf值在0.282502～0.282673范围内,εHf(t)变化为-6.9～-0.7,显示岩浆源自于岩石圈富集地幔部分熔融并在上升过程中受地壳物质的混染,为岩石圈伸展环境的产物。 相似文献
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The genetic structure of populations is often shaped by the reproductive system and larval properties of the species. The waratah anemone (Actinia tenebrosa) reproduces through both asexual clones, which have very short-distance dispersal, and sexual larvae, which are believed to disperse much greater distances. The impact of this mixed strategy on the New Zealand population structure of Actinia tenebrosa was investigated using microsatellite markers. The analysis incorporated 24 sampling locations from around New Zealand and one Australian location, using four microsatellite markers, n = 420. We observed low connectivity and high genetic differentiation between all locations sampled, with a distinct pattern of isolation by distance. The most distinct grouping of locations sampled was the north-east of the North Island from Cape Reinga to East Cape, which was identified by SAMOVA and STRUCTURE analyses as being moderately diverged from the remainder of the country. A tentative correlation was observed between genetic clustering and biogeographic regionalisation, where the distribution of a number of genetic clusters matched previously defined biogeographic regions. Within each location sampled, large numbers of clones were present and a latitudinal cline was observed in the relative contribution of asexually and sexually generated recruits, with an increase in asexual recruits on the South Island's east coast. 相似文献
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安徽宁芜地区铁氧化物-磷灰石矿床中金云母Ar-Ar定年及其地球动力学意义 总被引：23，自引：11，他引：12
铁氧化物-磷灰石型铁矿床是长江中下游成矿带的重要组成部分,对其成岩成矿时限的精确厘定,是理解长江中下游地区中生代大规模成矿作用的动力学演化的关键。本文分别对宁芜盆地南部白象山、和睦山及中部的陶村三个大-中型铁矿床中与磁铁矿密切共生的金云母单矿物进行了Ar-Ar同位素测年,获得白象山矿床金云母Ar-Ar坪年龄为134.9±1.1Ma,对应的反等时线年龄为133±2Ma;和睦山矿床金云母Ar-Ar坪年龄为132.9±1.1Ma,对应的反等时线年龄为133.9±2.4Ma;陶村矿床金云母的反等时线年龄为128±14Ma。该区铁氧化物-磷灰石型矿床与该区火山-次火山岩具有密切的时间联系,成岩成矿时限主要集中于135～126Ma。综合研究表明,长江中下游第二期成岩成矿作用的时限为135～126Ma,对应于岩石圈的大规模快速减薄的地球动力学背景。 相似文献
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R.V.DESYATKIN 《资源与生态学报(英文版)》2011,(3):272-276
Issues about land resources of cryolithozone and their possible transformation under global change conditions we will consider on example of the large region of the Russian Federation-the Republic of Sakha (Yakutia),which is considered as the center of the underground continental glaciation of earth in present conditions. 相似文献
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Deposits of Fe-Si-Mn oxyhydroxides are commonly found on the seafloor on seamounts and mid-ocean spreading centers. At Franklin Seamount located near the western extremity of Woodlark Basin, Papua New Guinea, Fe-Si-Mn oxyhydroxides are being precipitated as chimneys and mounds upon a substrate of mafic lava. Previous studies have shown that the vent fluids have a low temperature (20–30°C) and are characterized by a total dissolved iron concentration of 0.038 mM kg-1, neutral pH (6.26) and no measurable H2S. The chimneys have a yellowish appearance with mottled red–orange patches when observed in situ from a submersible, but collected samples become redder within a few hours of being removed from the sea. The amorphous iron oxyhydroxides, obtained from active and inactive vents, commonly possess filamentous textures similar in appearance to sheaths and stalks excreted by the iron-oxidizing bacteria Leptothrix and Gallionella; however, formless agglomerates are also common. Textural relationships between apparent bacterial and non-bacterial iron suggest that the filaments are coeval with and/or growing outwards from the agglomerates. The amorphous iron oxyhydroxides are suggested to precipitate hydrothermally as ferrosic hydroxide, a mixed-valence (Fe2+-Fe3+) green–yellow iron hydroxide compound. Consideration of the thermodynamics and kinetics of iron in the vent fluid, suggest that the precipitation is largely pH controlled and that large amounts of amorphous iron oxyhydroxides are capable of being precipitated by a combination of abiotic hydrothermal processes. Some biologically induced precipitation of primary ferric oxyhydroxides (two-XRD-line ferrihydrite) may have occurred directly from the fluid, but most of the filamentous iron micro-textures in the samples appear to have a diagenetic origin. They may have formed as a result of the interaction between the iron-oxidizing bacteria and the initially precipitated ferrosic hydroxide that provided a source of ferrous iron needed for their growth. The processes described at Franklin Seamount provide insight into the formation of other seafloor oxyhydroxide deposits and ancient oxide-facies iron formation. 相似文献
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I.V.Ashchepkov S.S.Kuligin N.V.Vladykin H.Downes M.A.Vavilov E.N.Nigmatulina S.A.Babushkina N.S.Tychkov O.S.Khmelnikova 《地学前缘(英文版)》2016,7(4):639-662
Mantle xenocrysts from early Triassic kimberlite pipes from Kharamai,Ary-Mastakh and Kuranakh fields in the Anabar shield of Siberia revealing similar compositional trends were studied to estimate the superplume influence on the subcratonic lithosphere mantle(SCLM).Pressure-temperature(PT) reconstructions using monomineral thermobarometry for 5 phases show division of the SCLM beneath the Kharamai field into 6 units:pyroxenitic Fe-rich(1-2 GPa) and Mg-rich(2-3 GPa) layers;middle with two levels of Gar-Sp pyroxenites at ~3 and 4-5 GPa;Gar-dunite-harzburgites ~4.5-6.5 GPa subjected to Ilm-Px vein metasomatism;and a Mg-rich dunite lower part.In the Anabar shield(Ary-Mastakh,Dyuken and Kuranakh fields) mantle lithosphere is composed of three large units divided into two parts:upper part with amphiboles and phlogopite;two levels of pyroxenites and eclogites at 3 and 4 GPa,and a lower part composed of refertilized dunites.Diagrams showing P-Fe~#Gar clusters for garnets and omphacites illustrate the differences between SCLM of these localities.Differences of Triassic SCLM from Devonian SCLM are in simple layering;abundance of Na-Cr-amphiboles and metasomatism in the upper SCLM part,thick pyroxenite-eclogite layer and lower part depletion,heated from SCLM base to 5.0 GPa.Kharamai mantle clinopyroxenes represent three geochemical types:(1) harzburgitic with inclined linear REE,HFSE troughs and elevated Th,U;(2) lherzolitic or pyroxenitic with round TRE patterns and decreasing incompatible elements;(3) eclogitic with Eu troughs,Pb peak and high LILE content.Calculated parental melts for garnets with humped REE patterns suggest dissolution of former Cpx and depression means Cpx and garnets extraction.Clinopyroxenes from Ary-Mastakh fields show less inclined REE patterns with HMREE troughs and an increase of incompatible elements.Clinopyroxenes from Kuranakh field show flatter spoon-like REE patterns and peaks in Ba,U,Pb and Sr,similar to those in ophiolitic harzburgites.The PT diagrams for the mantle sections show high temperature gradients in the uppermost SCLM accompanied by an increase of P-Fe~#Ol upward and slightly reduced thickness of the mantle keel of the Siberian craton,resulting from the influence of the Permian-Triassic superplume,but with no signs of delamination. 相似文献
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To investigate regional drivers of spatial patterns in macro- and meio-faunal community structure (abundance, biomass and taxonomic diversity) and ecosystem function (sediment community oxygen consumption [SCOC]), we sampled two regions in close proximity on New Zealand's continental margin—the Chatham Rise and the Challenger Plateau. Sites (n = 15) were selected in water depths ranging from 266–1212 m to generate a gradient in sedimentary properties and, in particular, surface pelagic productivity. Both macro- and meio-fauna abundance and biomass was 2–3.5 times higher on the Chatham Rise than on the Challenger Plateau, reflecting regional differences in pelagic primary production. We also found significant inter- and intra-regional differences in macro-fauna taxonomic diversity with two distinctive site groupings in each region. Univariate and multivariate measures of macro-fauna community attributes were most strongly correlated with sediment photosynthetic pigment (explaining 24%–59% of the variation). Sediment pigment content was as equally important in explaining meio-fauna community structure (36%–7%). Unlike community structure, SCOC was most strongly correlated with depth (44%), most likely reflecting temperature effects on benthic metabolism. Our results highlight the importance of a benthic labile food supply in structuring infaunal communities on continental margins and emphasise a tight coupling between pelagic and benthic habitats. 相似文献
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SD Kirkby 《Applied geography (Sevenoaks, England)》1996,16(4):289-303
To manage secondary dryland salinization successfully a coordinated regional management approach must be implemented. This paper considers the development of an interactive land classification methodology that identifies key land areas associated with the problem and then conveys information regarding the decision-making process to the end user. The developed system, Salt Manager, utilizes an expert system, a geographic information system, remotely sensed information and a relational database management system to implement the land classification method. Consideration is given in the paper to the salinization process, the problem of system integration and the provision of contextual information via graphic and textual formats. 相似文献
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