Multiple Episodes of Fluid-Rock Interaction in Meta- Anorthosite Northwest of the Idaho Batholith

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The Boehls Butte anorthosite is exposed within the broad border zone of the northern Idaho batholith and has experienced multiple episodes of fluid-rock interaction, including magmatic, regional metamorphic and meteoric-hydrothermal events. This study will examine the stable isotopic and geochemical effects of superimposed fluid-rock interaction on the anorthosite and metasediments at its contact. The objectives of this study are (1) to differentiate the isotopic and geochemical effects of post-metamorphic and synmetamorphic fluid-rock interaction, (2) to constrain the relative contributions of igneous, metamorphic and hydrothermal processes to the development of unique mineralogies and isotopic compositions in the anorthosite and (3) to determine the extent to which regional metamorphism was accompanied by, or merely overprinted by, hydrothermal fluid convection associatated with batholith intrusion. Fluid-rock interaction will be characterized by a combine study of stable isotopes, fluid inclusions, mineral-fluid equilibria and trace element geochemistry. The results will constrain the depth, magnitude and timing of convective fluid flow through metamorphic rocks in the border zone of the batholith, constraining the efficacy of deep-seated fluid convection as a dynamic process in regional metamorphism.