Book reviews     

Edith Brown Weiss  M. I. Budyko  Robert J. McAfee  Lester Machta 《Climatic change》1979,2(1):93-98

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Large-volume in-situ filtration of deep Pacific waters: Mineralogical and radioisotope studies     

S. Krishnaswami  D. Lal  B.L.K. Somayajulu  R.F. Weiss  H. Craig 《Earth and Planetary Science Letters》1976,32(2):420-429

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Announcement     

N.C. Gay  L.E. Weiss 《Tectonophysics》1974,24(3):287-300

This paper describes the results of a series of experiments carried out on card decks and foliated rock in order to study the nucleation and growth of kinks. Parameters varied in the experiments were confining pressure and the angle of inclination between the foliation and the direction of maximum shortening.The results showed that most kinks initiated as symmetric or monoclinal buckles which rapidly changed to an angular, stable form similar to that observed in nature. The amount of strain required to set up this stable geometry is small. The effect of increasing confining pressure is to diminish the size of the kinks while that of changing the angle of inclination of the foliation to the direction of maximum shortening is to modify the style of deformation from the development of a set of conjugate kinks at small angles (0 – 5°), to a single set of kinks at larger angles (5 – 15°), and, finally, to a combination of sliding along the foliation and kinking at the largest angles (15 – 30°) investigated.During this change in mode of deformation, the angular relationships between the kinks and the directions of the applied loads change systematically and graphs are presented which may be of use in relating the geometry of natural kinks to the principal stress directions.  相似文献   

The geochemistry of major and selected trace elements in a forested peat bog, Kalimantan, SE Asia, and its implications for past atmospheric dust deposition     

Dominik Weiss  William ShotykJack Rieley  Susan PageMarlies Gloor  Steve ReeseAntonio Martinez-Cortizas 《Geochimica et cosmochimica acta》2002,66(13):2307-2323

Biogeochemical processes in a forested tropical peat deposit and its record of past atmospheric dust deposition were assessed using the vertical distribution of lithophilic and plant essential elements in a dated core profile from Borneo, SE Asia. Peat formation started ∼22,120 ¹⁴C yr before present (BP), and Ca/Mg mass ratios of the solid peat and very low ash contents indicate a strongly ombrotrophic character throughout the deposit, implying that most of the inorganic fraction has been supplied exclusively by atmospheric inputs. Concentration profiles of Mn, Sr, and Ca suggest a very minor influence of chemical diagenesis in the underlying sediments. Silicon, Ca, Mg, P, S, and K show a strong and extended zone of enrichment in the top 200 cm of the profile, indicating that biological accumulation mechanisms are much more extensive than in temperate peat bogs.In the lower core sections, where the element distribution is dominated solely by past atmospheric deposition, average Al/Ti ratios are similar to the upper continental crust (UCC), whereas Fe is slightly enriched and Si is strongly depleted: this condition favors highly weathered tropical soil dust as the main inorganic mineral source. Significant correlation of Al, Fe, Si, S, Ca, and Ti with the lithophilic elements Y and Zr suggests that the distribution of these elements is controlled by sources of atmospheric mineral dust. The Ca/Mg, Ca/K, and Mg/K ratios of the collected rainwater samples are similar to the global average of continental rainwater and suggest a continental character for the site. This is supported by the similarity of the average concentration of Br, Mg, Ca, and S to that in temperate continental and maritime bogs in Switzerland and Scotland.The concentration profiles of Si, Fe, Al, and Ti show distinct peaks within the profile, implying enhanced dust deposition, reduced rates of peat accumulation, or possibly both owing to climatic changes during the Holocene. Enhanced dust deposition between ∼10,830 and 9060 ¹⁴C yr BP is tentatively interpreted as a Younger Dryas-like event with dust fluxes of ∼10.8 mg/m²/yr. The variations in Al/Ti and Fe/Ti profiles suggest that mineral dust sources have been changing constantly during the Holocene, with local sources being dominant between ∼7820 and 9500 ¹⁴C yr BP and long-range transport (derived most likely from China) being important during the late Pleistocene and early Holocene and from ∼7820 ¹⁴C yr BP to the present.  相似文献   

The puzzling structure of a sunspot     

Steven Tobias  Nigel Weiss 《Astronomy& Geophysics》2004,45(4):4.28-4.33

Why does a sunspot look the way it does? Steven Tobias and Nigel Weiss find answers to this question, by relating new high-resolution observations to recent theoretical studies of the spot's magnetic field.  相似文献   

AGAGE Observations of Methyl Bromide and Methyl Chloride at Mace Head, Ireland, and Cape Grim, Tasmania, 1998–2001     

P. G. Simmonds  R. G. Derwent  A. J. Manning  P. J. Fraser  P. B. Krummel  S. O'Doherty  R. G. Prinn  D. M. Cunnold  B. R. Miller  H. J. Wang  D. B. Ryall  L. W. Porter  R. F. Weiss  P. K. Salameh 《Journal of Atmospheric Chemistry》2004,47(3):243-269

In situ AGAGE GC-MS measurements of methyl bromide (CH₃Br) and methyl chloride (CH₃Cl) at Mace Head, Ireland and Cape Grim, Tasmania (1998–2001) reveal a complex pattern of sources. At Mace Head both gases have well-defined seasonal cycles with similar average annual decreases of 3.0% yr⁻¹ (CH₃Br) and 2.6% yr⁻¹ (CH₃Cl), and mean northern hemisphere baseline mole fractions of 10.37 ± 0.05 ppt and 535.7 ± 2.2 ppt, respectively. We have used a Lagrangian dispersion model and local meteorological data to segregate the Mace Head observations into different source regions, and interpret the results in terms of the known sources and sinks of these two key halocarbons. At Cape Grim CH₃Br and CH₃Cl also show annual decreases in their baseline mixing ratios of 2.5% yr⁻¹ and 1.5% yr⁻¹, respectively. Mean baseline mole fractions were 7.94 ± 0.03 ppt (CH₃Br) and 541.3 ± 1.1 ppt (CH₃Cl). Although CH₃Cl has astrong seasonal cycle there is no well-defined seasonal cycle in the Cape Grim CH₃Br record. The fact that both gases are steadily decreasing in the atmosphere at both locations implies that a change has occurred which is affecting a common, major source of both gases (possibly biomass burning) and/or their major sink process (destruction by hydroxyl radical).  相似文献   

APu heat source in marine coastal sediment: formation of a protective concretion     

Herbert V. Weiss  Dan Pavone 《Applied Geochemistry》1986,1(6)

The effect of the marine environment upon a vented Ir-encapsulated²³⁸Pu heat source was investigated. The heat source was emplaced in coastal submarine feldspathic sediment. In less than a month it became encased in a rock-like concretion. The capsule was cemented initially with a white deposit of anhydrite, a mineral identified with high temperature deep-sea springs. As the concentration increased in thickness sedimentary particles were incorporated by the cementing agent. A non-porous barrier was formed such that decay product He was impeded from escape. This property protected the heat source against intrusion by the corrosive marine waters.As determined by neutron activation, the major and minor elements within the coastal sediment, various fractions of the concretion, and certain discrete entities within or on the surface of the concretion, are included.  相似文献   

Chemical Separation and Isotopic Variations of Cu and Zn From Five Geological Reference Materials   总被引：6，自引：0，他引：6  

John B. Chapman  Thomas F.D. Mason  Dominik J. Weiss  Barry J. Coles  Jamie J. Wilkinson 《Geostandards and Geoanalytical Research》2006,30(1):5-16

This paper presents an adapted anion exchange column chemistry protocol which allowed separation of high-purity fractions of Cu and Zn from geological materials. Isobaric and non-spectral interferences were virtually eliminated for consequent multiple-collector ICP-MS analysis of the isotopic composition of these metals. The procedure achieved ∼ 100% recoveries, thus ensuring the absence of column-induced isotopic fractionation. By employing these techniques, we report isotopic analyses for Cu and Zn from five geological reference materials: BCR-027 blende ore (BCR), δ⁶⁵Cu = 0.52 ± 0.15‰ (n = 10) and δ⁶⁶Zn = 0.33 ± 0.07‰ (n = 8); BCR-030 calcined calamine ore (BCR), δ⁶⁶Zn = -0.06 ± 0.09‰ (n = 8); BCR-1 basalt (USGS), δ⁶⁶Zn = 0.29 ± 0.12‰ (n = 8); NOD-P-1 manganese nodule (USGS), δ⁶⁵Cu = 0.46 ± 0.08‰ (n = 10) and δ⁶⁶Zn = 0.78 ± 0.09‰ (n = 9); SU-1 Cu-Co ore (CCRMP), δ⁶⁵Cu = -0.018 ± 0.08‰ (n = 10) and δ⁶⁶Zn = 0.13 ± 0.17‰ (n = 6). All uncertainties are ± 2s; copper isotope ratios are reported relative to NIST SRM-976, and zinc isotope ratios relative to the Lyon-group Johnson Matthey metal (batch 3-0749 L) solution, JMC Zn. These values agree well with the limited data previously published, and with results reported for similar natural sample types. Samples were measured using a GVi IsoProbe MC-ICP-MS, based at the Natural History Museum, London. Long-term measurement reproducibility has been assessed by repeat analyses of both single element and complex matrix samples, and was commonly better than ± 0.07‰ for both δ⁶⁶Zn and δ⁶⁵Cu.  相似文献   

Speculations on the Thermal and Tectonic History of the Earth   总被引：3，自引：0，他引：3  

Dan McKenzie  Nigel Weiss 《Geophysical Journal International》1975,42(1):131-174

Summary. The connection between the Earth's thermal history and convection in the mantle is exploited to elucidate the early evolution of the Earth. It appears probable that convection extending over almost all of the mantle has dominated vertical heat transport throughout the whole of the Earth's history. Only in boundary layers at the surface and at a depth of 650–700 km is conduction likely to be important. The resulting evolution appears to be consistent with geological observations on early Precambrian rocks.
Various arguments are put forward in favour of two horizontal scales of convective flow in the mantle at depths less than 650 km. The large scale flow is related to the motion of major plates, and must be ordered over distances of more than 5000 km. Its evolution and energetics are discussed and there are no obvious problems in maintaining the proposed convective motions. Small scale flow with an extent of the order of 500 km appears necessary both to explain the heat flow through older parts of the Earth's surface and to reconcile the geophysical observations with the results of numerical experiments. Though the existence of the small scale flow is at present speculative, various tests of its presence are proposed.  相似文献   

The nature of blue luminescence from natural benitoite BaTiSi<Subscript>3</Subscript>O<Subscript>9</Subscript>     

M. ?GaftEmail author  L. ?Nagli  G. ?Waychunas  D. ?Weiss 《Physics and Chemistry of Minerals》2004,31(6):365-373

It is proved that blue luminescence from benitoite is connected with intrinsic luminescence centers, namely isolated TiO₆ octahedra. The metastable level ³T_1u is the emitting level at low temperatures with a long decay time of 1.1 ms. At higher temperatures an energy level with higher radiation probability must be involved in the emission process, and this level is situated at 0.06 eV higher than the lowest level. These two levels may be connected with ³T_1u level splitting or with closely spaced ³T_1u and ³T_2u levels. Decay time shortening and thermal quenching are connected with nonradiative decay within the TiO₆ luminescence center, while energy migration does not take place at least up to room temperature.  相似文献