Understanding the enhanced magnetization intensities of post-20 Ma oceanic basalts through magneto-mineratogical experiments

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The magnetization intensities of oceanic basalts vary through time, being clearly visible in marine magnetic anomaly profiles. Going from the present to the past, intensities decrease until around 20 Ma, and then they steadily increase until the Cretaceous. The initial decrease in intensity can be explained by low temperature oxidation of titanomagnetite to titanomaghemite; however, the cause for the subsequent increase in magnetization for oceanic basalts older than 20 Ma is unknown. We propose to test the possibility that magneto-mineralogical changes are the underlying cause of the magnetization increase. Two potential magneto-mineralogical changes are envisaged—both will be examined by combining electron microprobe analyses, paleo-intensity experiments and rock magnetic characterization. Atomic Force Microscopy (AFM), Magnetic Force Microscopy (MFM) or Mössbaur spectroscopy will also be employed depending on the case. Employing this new, cutting-edge technology together with the more classical experiments should significantly constrain a first-order, yet still unresolved, problem in the Earth sciences.