The density of North Atlantic and North Pacific deep waters     

Frank J. Millero  Augustin Gonzalez  Peter G. Brewer  Alvin Bradshaw 《Earth and Planetary Science Letters》1976,32(2):468-472

The densities of seventeen samples of seawater from GEOSECS stations 27 (North Atlantic) and 217 (North Pacific) have been measured with a vibrating flow densimeter at 25°C. The densities of the deep samples were found to be 5 ± 1.5and16 ± 3.6ppm greater, for the North Atlantic and North Pacific, respectively, than predicted by the equation of state of Millero, Gonzalez and Ward (1976) derived for seawaters of constant relative composition. The results are in good agreement with the density anomalies predicted by Brewer and Bradshaw (1975) on the basis of the observed increase of dissolved silica, alkalinity and total carbon dioxide in oceanic deep waters. The application of these corrections results in an agreement with the Millero, Gonzalez and Ward (1976) equation of state to ±4 ppm.  相似文献   

Oceans: Karl K. Turekian 2nd edn. Prentice-Hall, 1976, 149 pp., S9.95 cloth, $5.95 paper     

Peter G. Brewer 《Geochimica et cosmochimica acta》1977,41(5):687

  相似文献   

Removal of²³⁰Th and²³¹Pa from the open ocean     

R.F. Anderson  M.P. Bacon  P.G. Brewer 《Earth and Planetary Science Letters》1983,62(1):7-23

Concentrations of²³⁰Th and²³¹Pa were measured in particulate matter collected by sediment traps deployed in the Sargasso Sea (Site S₂), the north equatorial Atlantic (site E), and the north equatorial Pacific (Site P) as well as in particles collected by in situ filtration at Site E. Concentrations of dissolved Th and Pa were determined by extraction onto manganese dioxide adsorbers at Site P and at a second site in the Sargasso Sea (site D).Dissolved²³⁰Th/²³¹Pa activity ratios were 3–6 at Sites P and D. In contrast, for all sediment trap samples from greater than 2000 m, unsupported²³⁰Th/²³¹Pa ratios were 22–35 (average 29.7). Ratios were lower in particulate matter sampled at shallower depths. Particles filtered at 3600 m and 5000 m at Site E had ratios of 50 and 40. Results show that suspended particulate matter in the open ocean preferentially scavenges Th relative to Pa. Most of the²³⁰Th produced by decay of²³⁴U in the open ocean is removed by adsorption to settling particulate matter. In contrast, less than 50% of the²³¹Pa produced by decay of²³⁵U is removed from the water column by this mechanism. Mixing processes transport the remainder to other sinks.  相似文献   

Removal of ²³⁰Th and ²³¹Pa at ocean margins     

Robert F. Anderson  Michael P. Bacon  Peter G. Brewer 《Earth and Planetary Science Letters》1983

Uranium, thorium and protactinium isotopes were measured in particulate matter collected by sediment traps deployed in the Panama Basin and by in-situ filtration of large volumes of seawater in the Panama and Guatemala Basins. Concentrations of dissolved Th and Pa isotopes were determined by extraction onto MnO₂ adsorbers placed in line behind the filters in the in-situ pumping systems.Concentrations of dissolved ²³⁰Th and ²³¹Pa in the Panama and Guatemala Basins are lower than in the open ocean, whereas dissolved ²³⁰Th/²³¹Pa ratios are equal to, or slightly greater than, ratios in the open ocean. Particulate ²³⁰Th/²³¹Pa ratios in the sediment trap samples ranged from 4 to 8, in contrast to ratios of 30 or more at the open ocean sites previously studied. Particles collected by filtration in the Panama Basin and nearest to the continental margin in the Guatemala Basin contained ²³⁰Th/²³¹Pa ratios similar to the ratios in the sediment trap samples. The ratios increased with distance away from the continent.Suspended particles near the margin show no preference for adsorption of Th or Pa and therefore must be chemically different from particles in the open ocean, which show a strong preference for adsorption of Th. Ocean margins, as typified by the Panama and Guatemala Basins, are preferential sinks for ²³¹Pa relative to ²³⁰Th. Furthermore, the margins are sinks for ²³⁰Th and, to a greater extent, ²³¹Pa transported by horizontal mixing from the open ocean.  相似文献   

Larval settlement behavior in the jellyfishAurelia aurita (Linnaeus) (Scyphozoa: Semaeostomeae)     

Robert H. Brewer 《Estuaries and Coasts》1978,1(2):120-122

The distribution of sessile marine invertebrates is often the consequence of the selection of a suitable substrate by motile larvae. Motile planulae larvae ofAurelia aurita (Linnaeus) are exposed to an artificial substrate in the laboratory to determine if they possess the capacity both for specific orientation and for discrimination of surface texture at time of attachment. More than 90% (P<0.001) of the planulae fasten to the underside of objects. As a result, developing scyphistomae hang with the oral surface downward as commonly encountered in the field. The effect of surface texture on planula attachment is equivocal; this may reflect an indifference to surface texture, a limited capacity to locomote across rough substrate, or a mechanism of response sensitive only to large surface irregularities. These results are compared with those obtained for the planulae ofCyanea capillata (Linnaeus). The planular effected orientation of the scyphistoma may be generally true for coastal representatives of the Semaeostomeae, and perhaps for other shallow water Scyphozoa (including the Class Cubozoa).  相似文献   

Petrogenesis of basement rocks of the upper rhine region elucidated by rubidium-strontium systematics     

Martin S. Brewer  Hans J. Lippolt 《Contributions to Mineralogy and Petrology》1974,45(2):123-141

Initial ⁸⁷Sr/⁸⁶Sr ratios have been plotted against time of formation for various rock-types in the Schwarzwald and Vosges basement areas. These data exhibit strong positive correlations between the two variables. The Schwarzwald data define two distinct trend lines on the diagram, for the time span 500 to 250 Ma ago. The first comprises the data from orthogneisses, diatexites and pre-tectonic granites and documents the Sr isotope evolution in the crust underlying the Sehwarzwald. This region of the crust had a ⁸⁷Rb/⁸⁶Sr ratio of about 1. The other is delineated by data points from the post-tectonic plutons. These form a band corresponding to the development of closed systems with ⁸⁷Rb/⁸⁶Sr ratios of between 10 and 20 as indicated by the slope of the band. The second trend is interpreted as resulting from the formation of large, stable, deep-seated magma chambers formed by segregation of anatectic melts during a phase of tectonism 330Ma ago. The high ⁸⁷Rb/⁸⁶Sr ratios of these magmas arose by fractional crystallization, in response to tectonic decompression, during the coalescence of the presumedly water-saturated melts. Data for rocks from the Vosges, taken from the literature, form a single development line. Its slope corresponds to a ⁸⁷Rb/⁸⁶Sr ratio of about 5 and the line is analogous to the second trend line defined by the Schwarzwald data. The differences in the Rb/Sr systematics between the two areas can be explained as resulting from the deeper level of erosion in the Vosges. An important implication for Rb/Sr studies is that co-magmatic rocks can have very different initial ⁸⁷Sr/⁸⁶Sr ratios so that discrepancies in this ratio between rock-types cannot be used to divide plutons into genetic suites. On the other hand essential information is contained in the Rb/Sr systematics of orogenic magmatic rocks, such as the Variscan plutons in the Schwarzwald, that cannot be obtained from geochemical and petrological studies alone.  相似文献   

Calculation of the visible-UV absorption spectra of hydrogen sulfide,bisulfide, polysulfides,and As and Sb sulfides,in aqueous solution     

JA?TossellEmail author 《Geochemical transactions》2003,4(1):28

Recently we showed that visible-UV spectra in aqueous solution can be accurately calculated for arsenic (III) bisulfides, such as As(SH)₃, As(SH)₂S^- and their oligomers. The calculated lowest energy transitions for these species were diagnostic of their protonation and oligomerization state. We here extend these studies to As and Sb oxidation state III and v sulfides and to polysulfides S _n ^2- , n = 2–6, the bisulfide anion, SH^-, hydrogen sulfide, H₂S and the sulfanes, S _n H₂, n = 2–5. Many of these calculations are more difficult than those performed for the As(iii) bisulfides, since the As and Sb(v) species are more acidic and therefore exist as highly charged anions in neutral and basic solutions. In general, small and/or highly charged anions are more difficult to describe computationally than larger, monovalent anions or neutral molecules. We have used both Hartree-Fock based (CI Singles and Time-Dependent HF) and density functional based (TD B3LYP) techniques for the calculations of absorption energy and intensity and have used both explicit water molecules and a polarizable continuum to describe the effects of hydration. We correctly reproduce the general trends observed experimentally, with absorption energies increasing from polysulfides to As, Sb sulfides to SH^- to H₂S. As and Sb(v) species, both monomers and dimers, also absorb at characteristically higher energies than do the analogous As and Sb(III)species. There is also a small reduction in absorption energy from monomeric to dimeric species, for both As and Sb III and v. The polysufides, on the other hand, show no simple systematic changes in UV spectra with chain length, n, or with protonation state. Our results indicate that for the As and Sb sulfides, the oxidation state, degree of protonation and degree of oligomerization can all be determined from the visible-UV absorption spectrum. We have also calculated the aqueous phase energetics for the reaction of S₈ with SH^- to produce the polysulfides, S _n H^-, n = 2–6. Our results are in excellent agreement with available experimental data, and support the existence of a S₆ species.  相似文献   

Anomalies in rare earth distributions in seawater: Gd and Tb     

Hein J.W. De Baar  Peter G. Brewer  Michael P. Bacon 《Geochimica et cosmochimica acta》1985,49(9):1961-1969

We have measured profiles of the rare earth elements (REE) in Atlantic and Pacific Ocean waters. The data, normalized versus shales, exhibit a pronounced anomaly in Gd relative to its neighbors Eu and Tb in the REE series such that the Gd concentrations are high by 30–50%. Closer inspection reveals that the anomaly is made up of both elevated Gd and depressed Tb concentrations, likely associated with solution chemistry shifts in the transition from an exactly half filled 4f electron shell. Anomalies in Gd and Tb solution complexation are also indicated by the Turner-Whitfield-Dickson speciation model. The overall trend of heavy REE(III) enrichment in seawater and the $\text{Gd}\text{Tb}$ anomaly described here tend to support scavenging as an important removal mechanism for the REE from seawater.  相似文献   

Reply to Van den Berg and Bledsoe's comment on Lewin and Brewer (2001) “Predicting Channel Patterns”, Geomorphology 40, 329–339     

John Lewin  Paul A. Brewer   《Geomorphology》2003,53(3-4):339-342

  相似文献   

华北北部中生代岩墙群   总被引：27，自引：19，他引：27  

邵济安  张履桥 《岩石学报》2002,18(3):312-318

岩墙群是深源岩浆浅侵位的产物，它可提供有关壳-幔演化的重要信息。通过华北北部大同早中生代碳酸岩-煌斑岩岩墙群、赤峰早中生代闪长玢岩岩墙群、林西中生代辉绿岩岩墙群、京北晚中生代双峰式岩墙群的对比研究，揭示了华北中生代存在的两次底侵作用及其相关的伸展作用。华北早、晚中生代岩墙群与晋北地区元古代岩墙群的初步对比，从一个侧面反映了华北壳幔的演变。  相似文献