巻号一覧
34 巻, 8 号
選択された号の論文の3件中1～3を表示しています
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Ö. ÖZDEMIR, W. O'REILLY1982 年 34 巻 8 号 p. 467-478
発行日: 1982年
公開日: 2010/09/14
ジャーナル フリーIn this investigation the intensity and stability of thermoremanence (TRM) acquired by synthetic titanomaghemites has been studied for the first time. The titanomaghemites have compositions derived by oxidation from the titanomagnetite compositions, Fe2.4Ti0.6O4, Fe2.3Ti0.6Al0.1O4 and Fe2.2Ti0.6Al0.2O4 and are in the monodomain state. Compositions over the complete oxidation range cannot normally acquire TRM as the Curie temperatures of the more highly oxidized compositions exceed the “inversion” temperature (-300°C) at which the titanomaghemites transform to a multiphase intergrowth. In the composition range studied, the intensity of TRM falls and stability against both alternating field and thermal demagnetization rises after maghemitization. In the laboratory experiments, maghemitization preceeds TRM acquisition. In submarine basalts TRM acquisition will preceed maghemitization. The monodomain TRM model suggests that the TRM intensity in the latter case will be higher than in the former. The fall in TRM (-80%) with increasing degree of maghemitization of the laboratory experiments is greater therefore than that which would be expected from the TRM-maghemitization sequence in nature. It would seem that other mechanisms than change in chemical composition (e.g. changes in microstructure) are needed to provide an explanation of any cases in which the intensities of remanence of deep sea basalts are believed to fall by amounts similar to those found in the present experiments.抄録全体を表示PDF形式でダウンロード (1067K) -
David BEAMISH1982 年 34 巻 8 号 p. 479-490
発行日: 1982年
公開日: 2010/09/14
ジャーナル フリーObservations of geomagnetic variation fields on South Georgia, in the Scotia Sea, have revealed an unusual polarisation anomaly in the horizontal components, whose characteristics cannot be accounted for by an ocean-edge effect model. In addition, vertical field transfer functions have been calculated in the period range 10-104s. Although the data obtained from only one station allows only a limited analysis, it is suggested that the anomalous geomagnetic response on South Georgia can be accounted for by lithospheric conductivity contrasts between the Scotia and South American Plates.抄録全体を表示PDF形式でダウンロード (1151K) -
F. H. CHAMALAUN, R. WALKER1982 年 34 巻 8 号 p. 491-507
発行日: 1982年
公開日: 2010/09/14
ジャーナル フリーA three component digital fluxgate magnetometer is described for use in Geomagnetic Deep Sounding experiments. The magnetometer is small, completely self contained and requires only a few minutes to install in the field. The design incorporates an INTEL 8748 microprocessor which allows the power consumption to be reduced such that three months of data, at 1min sampling interval are obtained using only two small 10 AH lead acid gel batteries. The data are recorded digitally on a magnetic C-60 cassette tape, and transferred via a specially designed tape reader, to a main frame computer within a few hours. The magnetometer has a resolution of 1nT, and its drift, when properly thermostatted by burial, is less than 1nT per day. Noise is about 0.6nT and variations with periods greater than 5min are faithfully recorded. The magnetometer has a dynamic range of ±80, 000nT. Its low cost allows 2-D arrays to be constructed with a modest budget.抄録全体を表示PDF形式でダウンロード (2980K)
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