Parallel, similar and constrained folds   总被引：1，自引：0，他引：1  

Arvid M. Johnson  Virginia J. Pfaff   《Engineering Geology》1989,27(1-4):115-180

Theoretical analysis of folding of viscous multilayers with free slip or bonding at layer contacts indicates that folds in such multilayers can be described in terms of three end-members:parallel, in which orthogonal thicknesses of layers are largely constant;similar, in which vertical thicknesses of layers and shapes of successive interfaces are essentially constant; andconstrained, in which amplitudes of anticlines and synclines decrease to zero at upper and lower boundaries. Constrained,internal folds form if the multilayer is confined by rigid media; parallel,concentric-like folds form if the multilayer is confined by soft media, provided soft interbeds are sufficiently thin for the stiff layers to fold as an ensemble. Similar,sinusoidal orchevron folds form throughout much of the thickness of a multilayer, for any stiffness of confining media, provided wavelengths of folds are short relative to the thickness of the multilayer or soft interbeds are sufficiently soft and thick for the stiff layers to act independently. The analysis shows that multilayer folds may have the same form regardless of whether the layer contacts are freely slipping or bonded.

The forms of folds in multilayers confined by media with different viscosities above and below depend on the viscosity contrast of the media. For no medium above and a rigid medium below, the forms are concentric-like in the upper part and internal in the lower part of the multilayer. For no medium above and a soft medium below, the folds are concentric-like throughout the multilayer.

The theory indicates that a useful way to analyze forms of folds in rocks or in experiments is in terms of component waveforms, as defined, for example, by Fourier series. The distributions of amplitudes of component waveforms throughout the multilayer appears to be diagnostic, reflecting contrasts in properties of the multilayer and its confining media. Analysis of a large fold in the central Appalachians, Pennsylvania, and of a smaller fold in the Huasna syncline, California, indicates that at least three component waveforms are required to produce the gross forms of those folds.

The theory closely predicts wavelengths and shapes of folds produced in analogous elastic multilayers, indicating that nonlinearities in material behavior, which are inherent in the elastic material but are absent in the viscous material, are less significant than nonlinearities in the boundary conditions, which are the same in elastic and viscous materials.  相似文献   

The solubility of SO2 and the dissociation of H2SO3 in NaCl solutions     

Frank J. Millero  J. Beter Hershey  George Johnson  Jia-Zhong Zhang 《Journal of Atmospheric Chemistry》1989,8(4):377-389

The pK ₁ ^* and pK ₂ ^* of H₂SO₃ have been determined in NaCl solutions as a function of ionic strength (0.1 to 6 m) and temperature (5 and 25 °C). The extrapolated values in water were found to be in good agreement with literature data. The experimental results have been used to determine the Pitzer interaction parameters for SO₂, HSO ₃ ^- and SO ₃ ^- in NaCl solutions. The resultant parameters for NaHSO₃ and Na₂SO₃ were found to be in reasonable agreement with the values for NaHSO₄ and Na₂SO₄. It, thus, seems reasonable to assume that the interactions of Mg²⁺ and Ca²⁺ with HSO ₃ ^- and SO ₃ ^- can be estimated from the values with HSO ₄ ^- and SO ₄ ^- until experimental values are available. Measurements of pK ₁ ^* and pK ₂ ^* in artificial seawater were found to be in good agreement with the calculated values using the derived Pitzer parameters. It is, thus, possible to make reasonable estimates of the activity coefficients of HSO ₃ ^- and SO ₃ ^- ions and pK ₁ ^* and pK ₂ ^* for the ionization of H₂SO₃ in marine aerosols.  相似文献   

Magma genesis in the New Britain island-arc: Constraints from Nd and Sr isotopes and trace-element patterns     

D. J. DePaolo  R. W. Johnson 《Contributions to Mineralogy and Petrology》1979,70(4):367-379

A selected suite of fresh volcanic rocks from the New Britain island arc has been analyzed for ¹⁴³Nd/¹⁴⁴Nd, ⁸⁷Sr/⁸⁶Sr, major and trace elements to investigate relationships between isotopes, trace elements and petrology, and depth to the underlying Benioff zone. From these relationships inferences about magma generation are made utilizing Nd and Sr isotope systematics in possible source materials. Lavas ranging in composition from basalt to rhyolite show minimal variation of ¹⁴³Nd/¹⁴⁴Nd. Small variations in ⁸⁷Sr/⁸⁶Sr do not correlate with depth to the Benioff zone, but are related to magma type. Nd-Sr isotopes suggest that island arc lavas in general are derived from a mixture of suboceanic mantle and hydrothermally altered mid-ocean ridge-type basalt, but the New Britain magma source appears homogeneous with little indication of either the involvement of oceanic crust or mantle inhomogeneity. Trace element patterns in New Britain lavas are not consistent with Nd isotope data for currently accepted petrologic and trace element models of magma genesis. Mafic lavas from New Britain and other island arcs have anomalously high Sr/Nd, possibly due to components derived from subducted oceanic crust.  相似文献   

REE-fractionated trachytes and dacites from Papua New Guinea and their relationship to andesite petrogenesis   总被引：1，自引：0，他引：1  

I. E. M. Smith  S. R. Taylor  R. W. Johnson 《Contributions to Mineralogy and Petrology》1979,69(3):227-233

Minor trachyte and dacite temporally associated with, but spatially separated from, arc-trench type volcanoes in Papua New Guinea have distinctive REE abundances similar to experimentally produced and theoretically predicted partial melts of eclogite. However, modelling based on small amounts of equilibrium partial melting indicates that only fractionation involving a garnet-dominated residuum can account for the observed REE patterns if the source rock was subducted oceanic basalt. If the source was geochemically evolved, other mineral phases (e.g., amphibole) are possible in the residuum, and there is no necessity to postulate that the downgoing slab was the source for these magmas. The REE fractionated trachytes and dacites appear to be a part of the nearby late Cenozoic volcanic provinces, and possibly represent minor partial melts which only in unusual tectonic situations arrive unmodified at the Earth's surface.  相似文献   

Stable isotope compositions of olivine and dolomite in peridotites formed by deserpentinization,Darrington area,North Cascades,Washington     

Michael Johnson  Michael A Dungan  Joseph A Vance 《Geochimica et cosmochimica acta》1977,41(3):431-435

Oxygen isotope analyses of five olivines from the Darrington peridotite, Washington, yield δO¹⁸ values of +7.3 to +8.9%. which are consistent with derivation of these rocks from a serpentinite precursor. The isotopic data are compatible with mineralogical, textural and chemical evidence that most of the Darrington peridotites have formed by deserpentinization. Olivine from a single, petro-graphically distinct peridotite sample has a δO¹⁸-value of +5.2%. which is within the field of high-temperature olivines. The isotopic and textural evidence indicate that this is a partially recrystallized peridotite tectonite.Oxygen and carbon isotope analyses of dolomites from olivine-carbonate rocks indicate that they could have originated by introduction of atmospheric CO₂ via meteoric waters during the formation of ophidolomites or ophicalcites. Subsequent metamorphism and reequilibration have modified the δO¹⁸-values.  相似文献   

Experimental Determination of Thermoplastic Casing Collapse Pressures     

Roy C. Johnson  Jr.    Carl E. Kurt  George F. Dunham  Jr. 《Ground water》1980,18(4):346-350

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Hillslope stability and landslide hazard—a case study from Longdendale,north Derbyshire,England     

R.H. Johnson 《Proceedings of the Geologists' Association. Geologists' Association》1980,91(4):315-325

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Dissolution of Dense Chlorinated Solvents into Ground Water: 1. Dissolution from a Well-Defined Residual Source   总被引：3，自引：0，他引：3  

Michael R. Anderson  Richard L. Johnson  James F. Pankow 《Ground water》1992,30(2):250-256

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Comment on Blundy and Holland's (1990) “Calcic amphibole equilibria and a new amphibole-plagioclase geothermometer”     

Malcolm J. Rutherford  Marie C. Johnson 《Contributions to Mineralogy and Petrology》1992,111(2):266-268

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DISTRIBUTION OF DISSOLVED AND PARTICULATE TRACE METALS IN ANOXIC SEAWATER, SAANICH INLET, B . C. CANADA   总被引：2，自引：0，他引：2  

詹滨秋  C.S.Wong  K.W.Johnson 《中国海洋湖沼学报》1992,10(1):75-83

This paper discusses the spatial and seasonal distribution character of dissolved and paniculate trace metals in the anoxic seawater of Saanich Inlet, B.C., Canada. The study showed that concentration of dissolved and paniculate trace metals in anoxic seawater is closely related to (1) the concentration of H2S and the depth of the O2-H2S interface, (2) the exchange of seawater in Saanich Inlet with outside seawater, (3) biotic action, and (4) the flushing event. The study was based in part on the ratio between trace metals and nutrients. There was a steep change in the concentration of dissolved trace metals at the O2-H2S interface. The concentration of dissolved trace metals in the H2S-controlled zone was dependent on the H2S there. The suspended matter in Saanich Inlet comes from the Hero Strait seawater, phytoplankton production and resuspension of flushed-up sediments. The concentration of particulate trace metals was rather low in Saanich Inlet and tended to increase with depth. The total concentra  相似文献