Abstract
Shape and lattice orientation relations as well as chemical compositions of Fe-Ti-oxide micro-inclusions and plagioclase host crystals in rocks of a gabbro-plagiogranite assemblage from the Mid-Atlantic ridge at 13°34' N were studied using electron back scatter diffraction, transmission electron microscopy and field-emission gun-electron microprobe analyzer. Several evolutionary stages of the micro-inclusion-host assemblages were discerned, starting with precipitation of Fe-Ti-oxides from a super-saturated plagioclase in otherwise unaltered gabbro, followed by transformation and re-crystallization of the micro-inclusions as well as chemical alteration of both inclusions and host during plagiogranite intrusion and subsequent hydrothermal alteration. A detailed sequence of petrogenetic processes could be reconstructed. Fe-Ti-oxide micro-inclusions are the main carriers of the paleo-magnetic record of these rocks, and understanding the transformations affecting Fe-Ti-oxide micro-inclusions in the highly dynamic mid-ocean ridge environment is crucial for interpreting paleo-magnetic data.
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