Mineralogy and petrochemistry of the Huron Claim pegmatite, southeastern Manitoba

by Brian J. Paul

Institution: University of Manitoba
Degree: University of Manitoba
Year: 2013
Keywords: Huron Claim; pegmatite; Manitoba
Record ID: 2000867
Full text PDF: http://hdl.handle.net/1993/18866


The Huron Claim rare-element pegmatite is located in the Winnipeg River pegmatite district, southeastern Manitoba. The pegmatite outcrops within the Archean Bird River greenstone belt, in the western part of the English river subprovince of the Canadian Shield. The pegmatite is hosted within metagabbroic rocks of the Lamprey Falls formation, in which it forms a thin, sub-horizontal, tabular body crosscutting the foliation; it is approximately 100 m long and 45 m wide, and has a maximum thickness of 3.9 m. The pegmatite is relatively poorly zoned, with discontinuous units of aplite and graphic pegmatite (albite plus quartz) along its margins, units of medium to coarse-grained albite and blocky microcline-perthite in its interior, and a segmented quartz core. A poorly-defined and texturally variable albite "replacement" unit occurs in the central part of the pegmatite, and may partially replace the blocky microcline unit. Late, metasomatic veinlets of albite are present in the medium to coarse-grained albite unit, and a late, hydrothermal, calcium mineral assemblage occurs in some abundance throughout the pegmatite. The Huron Claim pegmatite is best classified as a fully-differentiated, partly albitized, gadolinite-type, blocky microcline-biotite pegmatite, containing significant amounts of Be, Nb>Ta, REE, U, Th, Zr>Hf and Rb. Rare-element minerals occuring within the pegmatite include beryl, columbite-tantalite, fersmite, microlite, niobian, rutile, euxenite (?), uraninite, monazite, zircon, thorite, niobian titanite, bavenite, bityite and bertrandite. The pegmatite is a member of the co-genetic Shatford Lake pegmatite group, but differs from the rest of the pegmatites in this group by its high U and Rb, low Sn and F, enrichment in LREE> (HREE+Y), extensive albite development, wide-spread metasomatic replacement of beryl and columbite-tantalite, and isolated location east of the Lac du Bonnet batholith. The pegmatite crystallized at intermediate crustal levels and is genetically linked to the Lac du Bonnet leucogranite. It probably formed by continued igneous differentiation at the quartz-feldspar minimum, coupled with separation of supercritical fluids from a volatile-oversaturated residual melt. Although it is a past producer of beryl, columbite-tantalite and feldspar, the Huron Claim pegmatite is of no commercial importance due to its small size.