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11.
Major elements can be modelled in ways similar to the quantitative petrogenetic modelling used for trace elements. In contrast to modelling with trace elements, however, modelling with major elements is constrained by the stoichiometry of the solid phases. Within these constraints, the same equations for partial melting and crystallization which have been used to such advantage for trace elements may be used for major elements.Calculated MgO and FeO abundances in a mantle-melt system are used as an example of the modelling technique. Such modelling yields limited fields of permissible melts and residues for a given parent composition, but does not give the paths of melting. It does allow the temperature and extent of melting which gave rise to a melt to be determined from the MgO and FeO abundances of the melt or residual solid. Applying the results of the modelling to igneous rocks and ultramafic nodules leads to the following conclusions, which are subject to the uncertainties in the available distribution coefficients. Least differentiated basalt glasses from the ocean floor are derived from parent melts with less than 15.5 weight % MgO and 8.2 wt. % FeO. Komatiites may be derived by less than 60% melting of a pyrolite source leaving a residue of olivine and pyroxene. Many nodules from the subcontinental mantle appear to be residues of large fractions of melting (>30%) at high temperature and pressure, whereas ultramafic nodules from oceanic basalts appear to be residues of smaller fractions of melting (<30%) at lower temperatures and pressures. 相似文献
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The characteristics of a boundary layer depend both on conditions at the surface and in the interior of the medium. In the undisturbed tropics, the latter are largely determined by subsidence and by infrared radiational cooling. One-dimensional models are used to establish relationships between the inversion height, subsidence, upper-air humidity and sea-surface temperature. In particular, it is shown that a universally colder tropical ocean would probably be covered by more extensive clouds.Contribution No. 1700 Rosenstiel School of Marine and Atmospheric Science, University of Miami. 相似文献
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Krahn MM Hanson MB Baird RW Boyer RH Burrows DG Emmons CK Ford JK Jones LL Noren DP Ross PS Schorr GS Collier TK 《Marine pollution bulletin》2007,54(12):1903-1911
“Southern Resident” killer whales include three “pods” (J, K and L) that reside primarily in Puget Sound/Georgia Basin during the spring, summer and fall. This population was listed as “endangered” in the US and Canada following a 20% decline between 1996 and 2001. The current study, using blubber/epidermis biopsy samples, contributes contemporary information about potential factors (i.e., levels of pollutants or changes in diet) that could adversely affect Southern Residents. Carbon and nitrogen stable isotopes indicated J- and L-pod consumed prey from similar trophic levels in 2004/2006 and also showed no evidence for a large shift in the trophic level of prey consumed by L-pod between 1996 and 2004/2006. ∑PCBs decreased for Southern Residents biopsied in 2004/2006 compared to 1993–1995. Surprisingly, however, a three-year-old male whale (J39) had the highest concentrations of ∑PBDEs, ∑HCHs and HCB. POP ratio differences between J- and L-pod suggested that they occupy different ranges in winter. 相似文献
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Nenad Grba Aleksandra Šajnović Ksenija Stojanović Vladimir Simić Branimir Jovančićević Goran Roglić Vladisav Erić 《Chemie der Erde / Geochemistry》2014
Sedimentary rocks from the saline formation of the Lopare Basin were investigated. Sediments contain a moderate amount of immature to marginally mature algal organic matter deposited under slightly reducing to anoxic and slightly saline to hypersaline conditions. Almost all of the samples contain β-carotane in a relatively high quantity, and in some, it represents the most abundant compound in the total distribution of hydrocarbons. The objective of the study was to determine the conditions that are favourable to precursors of β-carotene and/or the preservation of the carotenoid hydrocarbon skeleton. Moreover, the dominant transformation pathways of β-carotene under different redox and salinity conditions, which lead to the formation of aromatic carotenoids were defined. 相似文献
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Gary L Mills Alfred K Hanson James G Quinn William R Lammela N.Dennis Chasteen 《Marine Chemistry》1982,11(4):355-377
Dissolved organic matter (DOM) and dissolved copper-organic complexes were isolated from the estuarine waters of Narragansett Bay, RI, using reverse-phase liquid chromatography employing C18 Sep-Pak cartridges (Waters Associates). The cartridges were found to have a constant retention efficiency for processing ? 1-l volumes of seawater. Fractionation of the isolated material, by sequential elution of the Sep-Pak with water: methanol mixtures of increasing organic solvent concentration, yielded a fraction of the organic matter with a specific copper activity six times greater than the overall activity for the isolated DOM. Analysis of this fraction by high performance liquid chromatography suggested that the organic components are of intermediate polarity and have appreciable aromatic character.An investigation of the protonation characteristics of the isolated complexes indicated that most of the copper is associated with a broad range of acidic sites on the DOM. Analysis by electron paramagnetic resonance spectroscopy confirmed the organic association of the isolated copper and also suggested the presence of several types of binding sites which probably involve oxygen donor ligands.Studies of the exchange of 64Cu with these binding sites on the isolated DOM indicated that 70% of the sites undergo rapid exchange with copper in seawater while 20% of these sites did not exchange in a 24-h time period. 相似文献
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Summary Land-surface heterogeneity affects surface energy fluxes. The magnitudes of selected land-surface influences are quantified by comparing observations with model simulations of the FIFE (First ISLSCP Field Experiment) domain. Several plausible heterogeneous and homogeneous initial and boundary conditions are examined, although soilmoisture variability is emphasized. It turns out that simple spatial averages of surface variation produced biased flux values. Simulated maximum latent-heat fluxes were approximately 30 to 40 W m–2 higher, and air temperatures 0.4 °C lower (at noon), when computations were initialized with spatially averaged soil-moisture and leaf-area-index fields. The planetary boundary layer (PBL) height and turbulent exchanges were lower as well. It additionally was observed that (largely due to the nonlinear relationship between initial soil-moisture availability and the evapotranspiration rate), real latent-heat flux can be substantially less than simulated latent-heat flux using models initialized with spatially averaged soil-moisture fields. Differences between real and simulated fluxes also vary with the resolution at which real soil-moisture heterogeneity is discretized.With 8 Figures 相似文献
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