Electron Microscopy and Rock Magnetism of Ocean Floor Basalts with Implications for Paleo-Intensity Measurements

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9804765 Van der Voo A rock magnetic and electron microscope investigation, using convergent beam electron diffraction, is proposed for iron titanium oxides in ocean-floor basalts that vary between Recent and Jurassic in age, to determine the causes of the observed changes in intensity of marine magnetic anomalies and to examine their implications for paleo-intensity studies. Previously, the reduced magnetic intensity of older ocean-floor basalts was thought to be due to maghemitization, but recent observations have raised questions about this mechanism. If it can be shown that fine-grained titanomagnetite has not always been oxidized in older basalts, then it may well be a source of information about ancient geomagnetic intensities. Because ocean-floor basalts are abundant for times since 150 Ma, unoxidized titanomagnetites could become a promising tool for paleo intensity determinations.=20