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591.
Marchesi Claudio; Garrido Carlos J.; Bosch Delphine; Proenza Joaquin A.; Gervilla Fernando; Monie Patrick; Rodriguez-Vega Antonio 《Journal of Petrology》2007,48(9):1813-1840
We present whole-rock major- and trace-element and Nd–Sr–Pbradiogenic isotope data for Cretaceous igneous suites from easternCuba. These rocks are related to the Greater Antilles paleo-islandarc magmatism and have three different igneous styles. Group1 consists of tholeiitic basalts and rare basaltic andesitesthat have normal mid-ocean ridge basalt (N-MORB)-like compositionssimilar to those found in back-arc basin basalts (TiO2 = 1·2–2·9wt%; La/Yb(N) = 0·7–0·9, Th/Nb = 0·06–0·08,and initial 208Pb/ 204Pb = 37·65–37·74).Group 2 comprises basaltic and rare basaltic andesitic subvolcanicdykes with major- and trace-element and isotopic compositionssimilar to those of island arc tholeiites (TiO2 = 0·7–1·4wt%; La/Yb(N) = 0·6–0·9, Th/Nb = 0·06–0·68,and initial 208Pb/ 204Pb = 37·74–38·25).Group 3 is composed of low-Ti (TiO2 = 0·3–0·9wt%) calcalkaline igneous rocks that have an unambiguous subduction-relatedcharacter (La/Yb(N) = 1·1–5·0, Th/Nb = 0·35–1·55,and initial 208Pb/ 204Pb = 37·94–38·39).The parental magmas of the three groups formed by variable meltingdegrees (< 5–25%) of spinel lherzolite, with more depletedmantle sources for Groups 2 and 3 than Group 1. The trace-elementand radiogenic isotope compositions of primitive Group 3 samplesare strongly bimodal. One subgroup of samples is characterizedby low Ta/Yb (0·02–0·03) and Th/La (0·10–0·13),slightly subchondritic Nb/Ta (13·3–17·3),and relatively high initial 206Pb/204Pb (18·57–18·62)and Nd (7·6–9·4). The remaining primitiveGroup 3 samples have higher Ta/Yb (0·06–0·11)and Th/La (0·24–0·32), and highly subchondriticNb/Ta (7·6–9·1), coupled with lower initial206Pb/204Pb (18·24–18·29) and Nd (3·4–5·5).These signatures were induced by two distinct slab componentsthat mainly reflect the contributions of Cretaceous Atlanticmarine and North American continental sediments, respectively.Nb/Ta in the first subgroup was influenced by melting of rutile-bearingsubducted crust, whereas in the second it was inherited fromrecycled continental sediments. The involvement of Atlanticand North American sediments in Cuban Cretaceous magmatism indicatesthat the Proto-Caribbean (North American-Proto Atlantic) lithospheresubducted beneath the Greater Antilles arc during the Late Cretaceous(pre-Campanian), consistent with geotectonic models involvingonset of SW-dipping subduction beneath the Greater Antillespaleo-arc during the Aptian. The variable mantle source depletionand magnitude of the subduction component probably reflect differentsettings across the arc, from the arc front to a back-arc spreadingridge. KEY WORDS: eastern Cuba; Greater Antilles paleo-island arc; mantle source depletion; Nb/Ta fractionation; slab component 相似文献
592.
Chisholm Nicole Nagare Baban Wainwright Charlotte Creegan Ed Salehpoor Leyla VandenBoer Trevor C. Bullock Terry Croft Betty Lesins Glen Osthoff Hans Fernando H. J. S. Chang Rachel Y.-W. 《Boundary-Layer Meteorology》2021,181(2-3):345-364
Boundary-Layer Meteorology - Marine aerosols play an important role in the Earth’s climate, but their effects remain highly uncertain due to a poor understanding of their sources, properties,... 相似文献
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Transpiration in Quercus suber trees under shallow water table conditions: the role of soil and groundwater
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Clara A. Pinto Nadezhda Nadezhdina Jorge S. David Cathy Kurz‐Besson Maria C. Caldeira Manuel O. Henriques Fernando G. Monteiro João S. Pereira Teresa S. David 《水文研究》2014,28(25):6067-6079
Water is one of the major environmental factors limiting plant growth and survival in the Mediterranean region. Quercus suber L. woodlands occupy vast areas in the Iberian Peninsula, frequently under shallow water table conditions. The relative magnitude of soil and groundwater uptake to supply transpiration is not easy to evaluate under these circumstances. We recently developed a conceptual framework for the functioning of the root system in Q. suber that simulates well tree transpiration, based on two types of root behaviour: shallow connected and deep connected. Although this significantly improved knowledge on the functional traits of Mediterranean Q. suber, the approach has the limitation of requiring root sap flow data, which are seldom available. In this work, we present alternative methodologies to assess if trees are connected to groundwater and to estimate the soil and groundwater contributions to tree transpiration. We provide evidence on the tree unrestricted access to groundwater solely based on meteorological, stem sap flow and leaf water potential data. Using a soil mass balance approach, we estimated the yearly soil and groundwater contributions to tree transpiration: 69.7% and 30.3%, respectively. Groundwater uptake became dominant in the dry summer: 73.2% of tree transpiration. Results reproduce extremely well those derived from root modelling. Because of its simplicity both in formulation and data requirements, our approach is potentially liable to be adapted to other groundwater‐dependent Mediterranean oak sites, where interactions between land use and water resources may be relevant. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
597.
Ammar Mlayah Eduardo Anselmo Ferreira Da Silva Fethi Lachaal Samia Khadhar Abdelkrim Charef Fernando Noronha 《水文科学杂志》2013,58(3):686-705
Résumé Le Nord-Ouest de la Tunisie renferme plus que 81% des eaux de surface et 95% des mines et gîtes miniers. Le bassin versant de l'Oued Mellègue, situé dans cette zone, englobe 13 mines de plomb, zinc, fer, strontium, fluor, barium et phosphates. L'impact des rejets de ces mines sur les eaux de surface a été apprécié grâce à plusieurs compagnes d’échantillonnage. Les résultats d'analyse par ICP/MS de ces échantillons montrent qu'ils renferment des quantités non négligeables d'Al, As, B, Ba, Br, Cd, Co, Cr, Cu, Hg, Mo, Ni, Sr, U et de Zn. L'analyse des ces éléments dans les eaux du Mellègue, de ses affluents et dans la retenue de Nebeur montre que leurs concentrations sont inférieures aux normes d'eau potable. Ce comportement pourrait être dû à la nature des affleurements géologiques formés par des carbonates des argiles et des évaporites, à l'absence de cours d'eau drainant directement les rejets, à la formation de minéraux secondaires caractérisés par une importante rétention des métaux et à l’étendue des bassins versants non pollués. 相似文献
598.
A conceptual model for describing effective saturation in fractured hard rock is presented. The fracture network and the rock matrix are considered as an equivalent continuum medium where each fracture is conceptualized as a porous medium of granular structure and the rock matrix is assumed to be impermeable. The proposed model is based on the representation of a rough‐walled fracture by an equivalent porous medium, which is described using classical constitutive models. A simple closed‐form equation for the effective saturation is obtained when the van Genuchten model is used to describe saturation inside fractures and fractal laws are assumed for both aperture and number of fractures. The relative hydraulic conductivity for the fractured rock is predicted from a simple relation derived by Liu and Bodvarsson. The proposed constitutive model contains three independent parameters, which may be obtained by fitting the proposed effective saturation curve to experimental data. Two of the model parameters have physical meaning and can be identified with the reciprocal of the air entry pressure values in the fractures of minimum and maximum apertures. Effective saturation and relative hydraulic conductivity curves match fairly well the simulated constitutive relations obtained by Liu and Bodvarsson. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Guillermo Aravena Fernando Villate Ibon Uriarte Arantza Iriarte Berta Ibez 《Estuarine, Coastal and Shelf Science》2009,83(4):621-628
The effect of environmental factors (river discharge, water temperature and dissolved oxygen saturation) on the abundance and distribution of Acartia populations and the interactions between their congenerics was evaluated by means of transfer function (TF) models in the estuary of Bilbao during the period 1998–2005. The recorded species were Acartia clausi, Acartia tonsa, Acartia margalefi and Acartia discaudata. Acartia clausi dominated in the entire euhaline region of this estuary until 2003 when it was displaced from the inner part by A. tonsa. This invasive species (A. tonsa) was found for the first time in 2001 and colonized successfully the inner (salinity 30) and intermediate (salinity 33) waters of this estuary since 2003. The TF models revealed an immediate and negative effect of A. tonsa on A. clausi in the intermediate salinity (33) waters, where these species showed the highest spatial overlap. The results indicate that environmental changes from 2003 influenced the abundance of Acartia species, being unfavourable for A. clausi. The decrease of A. clausi abundance in low salinity waters was related to a significant decrease of dissolved oxygen saturation levels, whereas the increase of temperature was linked to a significant increase of A. tonsa. Acartia margalefi and A. discaudata were scarce over the entire period, but they were found to be valuable indicators of hydrological changes, which were associated to climate factors. These two latter species increased in abundance and expanded their seasonal distribution, and in the case of A. margalefi also its spatial distribution, in 2002, coinciding with the period in the time-series when autumn–winter rainfall and summer temperatures were lowest, and dissolved oxygen saturation levels were highest. 相似文献