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.

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.

The Usakos pegmatite, Namibia, is a highly evolved, rare-element LCT-type pegmatite. The pegmatite is emplaced in metasedimentary rocks of the Kuiseb formation. Ca and Al enrichment at the contact, B mineralization in the country rock and Sr mineralization in the core of the pegmatite are all evidence of interaction of the pegmatite melt and hosting country rock. K/Rb ratios within mica and feldspar are very low indicating a highly evolved melt. Tourmaline has a fractionation trend from Fe-rich at contact and intermediate areas to Fe-depleted in core regions and pockets. Columbite tantalite group minerals show a similar trend in fractionation, with columbite-(Fe) found near the pegmatite country rock contact and tantalite-(Mn) found in the core region. Trace element geochemistry from samples of pegmatite-country rock contact is enriched in light rare earth elements. Whole rock geochemistry provides evidence of the geochemically evolved nature of the pegmatite forming melt.

Suites of gem-quality faceted tourmaline, slices and fragments from Nigeria Namibia, Mali, Tanzania, Congo and Mozambique were quantitatively analyzed to determine mineralogy and minor elementChemistry. The specimens range in color from colorless to pink, red, yellowish-brown, green, bluish-gray, blue, brown and black. The results show that these tourmalines are elbaite, liddicoatite, rossmanite and schorl. Fe, Mn and Ti are the principal chromophores of the studied tourmaline. Fe is the most dominant and causes green, blue, dark-brown and black colors. Mn imparts pink and red hues. Correlations between Mn content and pink color intensity were not found. The Mn2+¡êTi4+ charge transfer causes yellowish-brown colors. A positive correlation of Na+ with transition element content was found. Limited relationships betweenChemistry and locality were deciphered for Nigeria, Namibia and Tanzania on the basis of endmember content and Congo based on Mn, Mg and Ti content.

In the Mojave Pegmatite district, located in northwestern AZ, numerous pegmatites intrude syn- to post-collisional Paleoproterozoic granitic rocks. The slightly older Cerbat plutons are associated with the suturing of the Mojave and Yavapai terranes whereas Aquarius granites were emplaced during the Yavapai Orogeny as the sutured terranes docked with North America. A detailed study of 5 pegmatites shows that they are zoned with composite cores and contain REE minerals characteristic of NYF pegmatites. However, they exhibit characteristics atypical for NYF pegmatites including F depletion, white microcline, an absence of columbite and, in the Rare Metals pegmatite, have muscovite and beryl. With the exception of the Kingman pegmatite, they exhibit normal LREE-HREE distributions. The Kingman pegmatite is extremely LREE enriched, HREE depleted and exhibits an unusual Nd enrichment which, in some cases, is sufficiently high that allanite is Nd dominant, thus a new mineral species, allanite-Nd.

This thesis focuses on heavy mineral species found in a unique carbonate assemblage in the Mt. Mica pegmatite in order to determine the conditions of their formation and their mineral paragenesis as well as to gain insight on the origin of this very unusual carbonate-rich unit.

No description available.

The Dumper Dew is a newly discovered pegmatite located on the eastfacing slope of Uncle Tom Mountain in Oxford County, Maine. It is a geochemically evolved LCT-type pegmatite petrogenetically linked to the middle Paleozoic Sebago batholith. Shallow emplacement of the Dumper Dew is evidenced by abundant miarolitic cavities found in the pegmatite. The sheet-like structure of the pegmatite coupled with its intrusion in lowmetamorphic grade country rock suggests rapid crystallization. Northern portions of the wall zone and intermediate zones have undergone hydrothermal alteration by the migration of late-stage fluids. The pegmatite hosts a diverse assemblage of rare-element mineral phases due to its high degree of geochemical fractionation. Trends of geochemical fractionation of individual mineral phases such as K-feldspar, muscovite, garnet, apatite, beryl, spodumene, triphylite-lithiophilite, tourmaline, cassiterite, and columbite-tantalite were attained via instrumentation assay. These trends illustrate an enhanced degree of magmatic differentiation relative to other pegmatites in the area.

The Bernic Lake Formation in the Bird River greenstone belt consists dominantly of mafic to felsic arc volcanic and volcaniclastic rocks, with varying amounts of mafic to felsic intrusive rocks, including the Bernic Lake pegmatite group. U-Pb geochronoligical analyses on selected samples around the Bernic Lake area, indicate that the Tanco gabbro, the Birse Lake granodiorite and the volcanic rocks of the Bernic Lake Formation are contemporaneous ca. 2724 Ma and form part of a singular volcanic and subvolcanic complex. The highly evolved, LCT-type, rare element-bearing Bernic Lake pegmatite group, including the world class Tanco pegmatite, was emplaced in the Bernic Lake Formation during a belt-scale tectonomagmatic event associated with G3 deformation between ca. 2650 and 2640 Ma. Early and rarely preserved isoclinal folding in the Bernic Lake Formation attributed to G1 deformation was followed north-south directed compression resulting in refolding and transposition of G1 structures by east-west trending upright F2 folds. Continued compression caused strain localization and south-side-up shearing along the North Bernic Lake Shear Zone (NBLSZ), which juxtaposes MORB-like basalt of the south panel to the south against arc rocks of the Bernic Lake Formation to the north. G3 deformation is characterized by a spaced S3 fracture cleavage that overprints the penetrative S2 fabric, and dextral reactivation of the NBLSZ. Pegmatitic melt ascended from depth along the reactivated NBLSZ during this time and was emplaced both within the shear zone and within rock units adjacent to it. The shapes and orientations of the pegmatites are controlled in part by the rheology of the host rocks into which they were emplaced. Rheologically competent lithologies responded to G3 strain by brittle fracture and the pegmatites occurring therein are flat and tabular; rheologically incompetent lithologies responded to G3 strain by ductile-brittle deformation and the pegmatites therein are irregular, folded, and/or boudinaged. The contrasting styles suggest that the pegmatites intruded while the rocks of the Bernic Lake Formation were at or near the brittle-ductile transition.

The Bernic Lake Formation in the Bird River greenstone belt consists dominantly of mafic to felsic arc volcanic and volcaniclastic rocks, with varying amounts of mafic to felsic intrusive rocks, including the Bernic Lake pegmatite group. U-Pb geochronoligical analyses on selected samples around the Bernic Lake area, indicate that the Tanco gabbro, the Birse Lake granodiorite and the volcanic rocks of the Bernic Lake Formation are contemporaneous ca. 2724 Ma and form part of a singular volcanic and subvolcanic complex. The highly evolved, LCT-type, rare element-bearing Bernic Lake pegmatite group, including the world class Tanco pegmatite, was emplaced in the Bernic Lake Formation during a belt-scale tectonomagmatic event associated with G3 deformation between ca. 2650 and 2640 Ma. Early and rarely preserved isoclinal folding in the Bernic Lake Formation attributed to G1 deformation was followed north-south directed compression resulting in refolding and transposition of G1 structures by east-west trending upright F2 folds. Continued compression caused strain localization and south-side-up shearing along the North Bernic Lake Shear Zone (NBLSZ), which juxtaposes MORB-like basalt of the south panel to the south against arc rocks of the Bernic Lake Formation to the north. G3 deformation is characterized by a spaced S3 fracture cleavage that overprints the penetrative S2 fabric, and dextral reactivation of the NBLSZ. Pegmatitic melt ascended from depth along the reactivated NBLSZ during this time and was emplaced both within the shear zone and within rock units adjacent to it. The shapes and orientations of the pegmatites are controlled in part by the rheology of the host rocks into which they were emplaced. Rheologically competent lithologies responded to G3 strain by brittle fracture and the pegmatites occurring therein are flat and tabular; rheologically incompetent lithologies responded to G3 strain by ductile-brittle deformation and the pegmatites therein are irregular, folded, and/or boudinaged. The contrasting styles suggest that the pegmatites intruded while the rocks of the Bernic Lake Formation were at or near the brittle-ductile transition.