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  • Springer  (11)
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  • 1
    Electronic Resource
    Electronic Resource
    Anhysteretic remanent magnetization (ARM) in magnetite grains (1971)
    Springer
    Pure and applied geophysics 91 (1971), S. 160-165 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary ARM has been measured in a range of inducing, steady fields up to 50 oersteds and for 6 sizes of magnetite grains with average diameters 5 μm to 174 μm. For all sizes a slight non-linearity of ARM with inducing field was found, apparently comprising a non-linear contribution independent of grain size plus a linear contribution which increased with decreasing grain size. In the largest grains induced ARM agreed well with multidomain grain theory. Relative enhancement of ARM in smaller grains is comparable to the enhancement of thermoremanence and therefore appears to indicate a pseudosingle domain contribution to ARM in small grains. However the observations allow an alternative explanation in terms of more extreme dimension ratios in the smaller grains. Presentation of the equations for multidomain ARM and TRM using observed instead of intrinsic susceptibilities makes it appear that the inadequacy of multidomain theory (and consequent necessity for pseudo-single domain theory) are less serious than has been supposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879565
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  • 2
    Electronic Resource
    Electronic Resource
    On the role of Brownian motion in the control of detrital remanent magnetization of sediments (1972)
    Springer
    Pure and applied geophysics 98 (1972), S. 139-145 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary The field dependence of magnetic remanence in laboratory deposited sediments is re-examined in terms of the average orientation of small grains of magnetite subject to the combined effect of an aligning field and thermal agitation. The classical (Langevin) formula for paramagnetic susceptibility is generalized to describe an assembly of grains with magnetic moments having a uniform distribution of values between zero and an upper limit, yielding a simple analytical expression in excellent accord with the pioneering measurements of Johnson, Murphy and Torreson. Comparison of theory and observation shows that the grain moments are intermediate between the values expected for single domains and multidomains, confirming the existence of pseudo-single domain effects, as deduced from observations of thermoremanence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00875588
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  • 3
    Electronic Resource
    Electronic Resource
    Field-induced anisotropy of magnetic susceptibility in rocks (1969)
    Springer
    Pure and applied geophysics 76 (1969), S. 123-129 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary An induced anisotropy of magnetic susceptibility results from the domain alignment which is produced by treating stationary specimens in a strong alternating field. Appreciable domain re-orientation occurs in fields as low as 50 oersteds and the effect must therefore normally be an important part of the process of alternating field demagnetization. Induced anisotropy has been measured in a number of igneous rocks with a range of palaeomagnetic stabilities and in magnetite powders of controlled grain sizes, dispersed in plaster or kaolin specimens which were mechanically deformed to produce instrinsic magnetic anisotropy by grain alignment. The saturation magnitude of the induced anisotropy is not a function of grain size but the saturating field required increases with decreasing grain size. In the larger grains, induced anisotropy is a function of grain orientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877845
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  • 4
    Electronic Resource
    Electronic Resource
    Thermal relaxation of magnetic domain misalignment in rocks (1969)
    Springer
    Pure and applied geophysics 76 (1969), S. 130-136 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary The anisotropy of susceptibility which is induced in rocks and dispersed powdered magnetite by the application of a strong alternating field is removed by heating more rapidly than is thermoremanence in the same specimens. The anisotropy associated with thermoremanence induced in the earth's field is negligible, but in fields greater than 5 oersteds it becomes appreciable. It is concluded that the domain structure associated with low field thermoremanence is only a very slight perturbation of the zero field structure. However this is much less simple than has been supposed and involves two- or three-dimensional domain closure. An appropriate minor revision of the theory of multidomain thermoremanence is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877846
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  • 5
    Electronic Resource
    Electronic Resource
    Theory of the piezomagnetic effect in titanomagnetite-bearing rocks (1972)
    Springer
    Pure and applied geophysics 97 (1972), S. 146-155 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary The stress sensitivitiesS x andS R of susceptibility and remanence for titanomagnetite-bearing rocks are calculated in terms of magnetostriction constantsλ 100 andλ 111 and anisotropy constantsK 1,K 2 of the magnetic minerals.S x andS R are represented by quite different algebraic expressions but happen to have comparable numerical values over the whole range of titanomagnetite compositions. Both increase strongly with titanium content. This leads to more optimistic calculations of tectonomagnetic effects than with the previously assumed stress sensitivity for pure magnetite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00875958
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  • 6
    Electronic Resource
    Electronic Resource
    A search for flow structure in columnar basalt using magnetic anisotropy measurements (1964)
    Springer
    Pure and applied geophysics 57 (1964), S. 61-65 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary Evidence for flow structure within hexagonal columns of basalt has been sought, using measurements of the anisotropy of magnetic susceptibility. The observed magnetic grain alignment indicates that the flow was essentially uniform and horizontal across the hexagons which were sampled. The flow probably occurred during emplacement of the lava; there is no evidence of convection within the hexagons, either from the degree of grain alignment or its orientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879709
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  • 7
    Electronic Resource
    Electronic Resource
    The seismomagnetic effect (1964)
    Springer
    Pure and applied geophysics 58 (1964), S. 5-22 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary Local variations in the geomagnetic field, which are produced by stress changes in crustal rocks, are calculable from the stress patterns and the piezomagnetic properties of the rocks down to the Curie point isotherm. Release of stress during movement along a section of a transcurrent fault at an angle ϕ, measured clockwise with respect to the direction of magnetization of the rocks, produces a change in field similar to that which would be produced by the addition of a buried dipole of orientation (2ϕ±π/2), the alternative signs applying to right- and left-lateral faults. Computed seismomagnetic anomalies of horizontal, vertical and total field are plotted for different fault orientations in simple geological environments. Time-dependent magnetic anomalies with magnitudes of the order 10 gammas may commonly accompany the build-up of stress before an earthquake and provide a pre-indication of it.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879136
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  • 8
    Electronic Resource
    Electronic Resource
    The volcano-magnetic effect (1965)
    Springer
    Pure and applied geophysics 62 (1965), S. 96-104 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary A geometrically simple volcano is considered, havig a spherical magma chamber of 2.5 km radius centred at 10 km depth. The Curie point isotherm is assumed to be a plane at 20 km depth, except for the spherical volume which is also non-magnetic. The stress pattern in the vicinity of the spherical chamber, due to regional stress of sufficient intensity to cause an eruptions, is used to calculate the change in magnetization which results from the piezomagnetic effect through the volume of solid rock. The consequent magnetic field anomaly at the surface is then obtaied by numerical integration of the dipole law of force over the stressed volume. For rocks of the type found on the volcanic island of St. Vincent (West Indies), this model gives a maximum local volcano-magnet c effect of about 7 gammas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00875290
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  • 9
    Electronic Resource
    Electronic Resource
    Magnetic anisotropy of laboratory materials in which magma flow is simulated (1966)
    Springer
    Pure and applied geophysics 64 (1966), S. 78-80 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary The magnetic anisotropy of lava flows has been simulated using plaster of Paris containing about 2% of nickel filings. The ellipsoid of magnetic anisotropy was oriented with its long axis close to but tilted with respect to the flow direction and its intermediate axis in the flow plane perpendicular to the flow direction; the same alignment was obtained with four different experimental conditions. This result is at variance with observations on basalt flows in which the long axis of the magnetic ellipsoid is perpendicular to the flow direction. It appears likely that the favoured alignment of elongated grains in a fluid or semi-fluid flow is sensitive to physical parameters which have not yet been examined adequately. Reliable magnetic determinations of flow directions in lavas must await clarification of this problem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00875533
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  • 10
    Electronic Resource
    Electronic Resource
    Measurements of thermal expansions of small mineral crystals (1982)
    Springer
    Physics and chemistry of minerals 8 (1982), S. 212-217 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract A capacitance micrometer has been developed for the measurement of thermal expansions of small crystals over moderate temperature ranges (approximately 100 K above laboratory temperature). Linear coefficients are obtained to ±0.5×10−6 K−1 and volume coefficients to ±1.5×10−6 K−1. New values are reported for 13 materials, obtained as crystals down to 1 mm in size. For many of these we obtained satisfactory agreement with earlier data, but exceptions are zircon (volume coefficient 6.6±1.6×10−6 K−1, compared with earlier values up to 21×10−6 K−1) and strontium fluoride (volume coefficient 57.9±2.2×10−6 K−1, compared with 42 to 49×10−6 K−1). The new data are combined with values of incompressibility, density and specific heat to obtain new values of Grüneisen's ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00309480
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