Osama Y. Abdel‑Aal
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Ph. D. Thesis
Alteration of Opaque Minerals and the Magnetization and Magnetic Properties of Volcanic Rocks in a Drill Hole From an Active Geothermal Area in the Azores.
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Two hundred and thirty-two polished sections representing ninety-four flow units, three agglomerates and three intrusions from a 981 m borehole drilled in the northern flank of the active volcano Agua de Pau were studied. Opaque minerals were found to be titanomagnetite and ilmenite and their alteration products. Mineralogical and microprobe studies show that both titanomagnetite and ilmenite were subjected to high temperature oxidation and hydrothermal alteration of different degrees in most of the drill core. A new classification of hydrothermal alteration of titanomagnetite and ilmenite in active geothermal areas is proposed.
One hundred and eleven samples were used for rock and paleomagnetic studies. The high Curie temperatures in the drill core indicate a high degree of overall oxidation and alteration. The variation in the magnetic parameters were related to the effect of oxidation and alteration on the magnetic phases. All the magnetic inclinations were normal, indicating a magnetization during Brunhes polarity. The possibility of self-reversal in the drill core was discussed and rejected.
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Pages: 284
Supervisors: James Hall