Igneous and High Temperature Hydrothermal Alteration Mineralogies in Drill-Recovered Peridotite from the Galicia Margin, Iberian Peninsula

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This is a proposal to study the primary mineralogy and composition of an upper mantle peridotite and its subsequent alteration. The peridotite samples are obtained from a 39.5 meter section of drill core obtained during ODP Leg 103 at the Galicia Margin. The study will involve petrographic and microprobe analyses of approximately 50 thin sections cut from various parts of the core, focusing on the central and least altered peridotite, in order to characterize the alteration mineralogies and textures, and to determine relict igneous minerals. Sr isotopic analyses will be performed in an attempt to determine the age of implacement and to further characterize the alteration history of the core. Some attempt will be made to incorporate these data into a coherent tectonic picture by estimating the P- T of the alteration assemblages. Studies such as this are of fundamental importance to understanding the tectonic and thermal evolution of the oceanic crust and upper mantle, and its penetration and alteration by circulating fluids.