共查询到20条相似文献，搜索用时 31 毫秒
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Maria Irene Bartolomeu Raposo 《Geophysical Journal International》1997,131(1):159-170
Magnetic fabric was determined by applying the anisotropy from the low-field magnetic susceptibility (AMS) technique in 62 mafic dykes from the Mesozoic Florianópolis (Santa Catarina Island) dyke swarm, southern Brazil. These dykes cut the crystalline basement rocks, which are mainly Proterozoic. They are vertical or subvertical in dip and trend mainly NE, although NW-trending dykes are also found. Dykes are tholeiitic in composition and are geochemically similar to those from the Ponta Grossa swarm. Thicknesses vary from 0.3 to 60 m. Polished sections show that titanomagnetites carry the AMS in these dykes. Hysteresis parameters show that the magnetic minerals fall in the PSD range. Two types of magnetic fabric are recognized. Type I is characterized by K 1 - K 2 parallel to the dyke wall, representing magma flow within the dykes; type II, with K 1 - K 3 parallel to the dyke wall, was found in four dykes. Type I is found in 94 per cent of the dykes, and approximately 20 per cent of these have K 1 inclinations of less than 30°, suggesting horizontal or subhorizontal flow. About 80 per cent have K 1 inclinations of greater than 30°, due to inclined to vertical flow. The comparison of AMS studies from both the Florianópolis and the Ponta Grossa dykes suggests a source position closer to Santa Catarina Island than the Ponta Grossa arch. 相似文献
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Multimodal investigation of thermally induced changes in magnetic fabric and magnetic mineralogy 总被引：1，自引：0，他引：1
Z. X. Li J. Dobson Z. Chen W. J. Chang & T. G. St. Pierre 《Geophysical Journal International》1998,135(3):988-998
Low-field magnetic susceptibility and its anisotropy (AMS) were measured for a suite of sandstone and siltstone samples. AMS orientations measured on two systems (Bartington and Digico) differed before thermal treatment of the samples but became the same after thermal demagnetization in air to 600 °C. Six position measurement schemes for the Bartington system do not eliminate the effects of specimen inhomogeneity and other errors, whereas 12- and 24-position measurements give good agreement with the Digico anisotropy meter and with the observed petrofabric. Thermal demagnetization from temperatures between 400 and 650 °C had the effect of enhancing both the magnetic susceptibility and AMS. Although the most profound mineralogical change due to heating was the conversion of kaolinite into metakaolin, IRM, XRD, DTA and Mössbauer spectroscopic analysis demonstrate that the changes in magnetic properties were due to the transformation upon heating of trace amounts of sulphides into magnetite and/or maghemite and haematite. Both magnetic susceptibility and the degree of anisotropy decrease with higher-temperature thermal demagnetization due to the oxidation of the newly formed magnetite and/or maghemite into haematite. The magnetic foliation of the newly formed magnetite/maghemite and haematite is parallel to the bedding, possibly following the orientation of the original sulphides. 相似文献
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Magnetic properties of the profiles of polluted and non-polluted soils. A case study from Ukraine 总被引：7，自引：0，他引：7
Maria Jele&#;ska Agata Hasso-Agopsowicz Barbara Kopcewicz Anatoliy Sukhorada Ksenija Tyamina Magdalena K&#;dzia&#;ko-Hofmokl Zhanna Matviishina 《Geophysical Journal International》2004,159(1):104-116
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A new 3-D inversion algorithm for magnetic total field anomalies 总被引：1，自引：0，他引：1
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