A study of the mineralology, textural zoning and geochemical characterisitics of the Buck claim pegmatite dike in southeastern Manitoba was undertaken to obtain data to use in interpreting the petrological and geochemical evolution of the dike. The dike is a sheet-like body of 1 to 10 m variable thickness and a known extent of 0.4 km north-south and 2.0 km east-west. It is intruded into metamorphosed rocks of upper greenschist to lower amphibolite facies, in the Bird River greenstone belt of the English River subprovince (westernSuperior Province). The dike forms a culmination at the point of the only known surface exposure, a small open-cut trench. The dike dips gently away from the surface exposure to the east and west. Internal zonation is well developed in the dike, although zone distribution is assymetric. The sequence of zones downward in the pegmatite is: a thin border zone of saccharoidal albite +/- quartz; a quartz-albite-muscovite-beryl-tourmaline wall zone; a cleavelandite-microcline perthite-quartz-muscovite-lithian muscovite-beryl-amblygonite intermediate zone; and a quartz-rich core zone containing microcline perthite, triphylite, amblygonite, petalite, pollucite and apatite. Similar zones exist below the core except for the absence of a lower border zone... Based on mineralogical, chemical and textural studies it is evident that the dike crystallized totally from a supercritical aqueous fluid without the direct involvement of a silicate melt phase. Subsequent to formation most of the primary assemblage of the dike was altered during an extensive phase of albitization. Hydrothermal and supergene alteration and depostion are evident as late stage processes of limited extent...