34 research outputs found
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Columbite-tantalite mineral chemistry from rare-element granitic pegmatites: Separation Lakeh area, N.W. Ontario, Canada
The Separation Lake area is host to the most important rare-element pegmatites in Ontario, Canada. They include the Big Whopper and Big Mack petalite pegmatite systems which potentially represent the world's second largest lithium deposit of this type. The pegmatites occur in two distinct clusters adjacent to the Separation Rapids pluton which is thought to be the source of the rare-elements. Beryl-type and complex-, petalite-subtype pegmatites are the most common and a few pegmatites have characteristics similar to the lepidolite-subtype. This study reveals that columbite-tantalite in the pegmatites has an extremely wide range of composition from primitive ferrocolumbite to evolved, almost end-member manganotantalite. Evidence is provided that melt evolution resulted in increased fluorine activity (as seen in microlite compositions) and that in situ fractionation of magma within individual pegmatites often led to the crystallization of rare-element-enriched, Li mica-fluorapatite-cleavelandite pods. Zonation patterns seen in backscattered electron images show primary compositions of columbite-tantalite were modified by secondary processes related to extreme fractionation and involving the late stage development of albitic units in individual pegmatites. This alteration led to recrystallization of columbite-tantalite and produced compositions with lower Ta contents, but with little change in Mn content
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Rare-element mineralization of the Separation Lake area, northwest Ontario: characteristics of a new discovery of complex-type, petalite-subtype, Li-Rb-Cs-Ta pegmatite
Abstract not available
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Project Unit 04-039. Rare-element granitic pegmatites of the Fort Hope Field, North-Central Ontario
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New discovery of rare-element pegmatite mineralization, Separation Lake area, northwestern Ontario
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Rare-metal exploration potential of the Separation Lake area: an emerging target for Bikita-type mineralization in the Superior Province of Ontario
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Project Unit 93-11. Granite-related mineralization in Northwestern Ontario: IV. New Rare-Element Pegmatite Discoveries in the Separation Lake Area
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Project Unit 93-11. Granite-related mineralization in Northwestern Ontario: II. Detailed examination of the Separation Rapids (English River) rare-element pegmatite group
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Liddicoatite and associated species from the McCombe spodumene-subtype rare-element granitic pegmatite, Northwestern Ontario, Canada
Liddicoatite, a rare species of tourmaline, has been found in the McCombe pegmatite, of complex type and spodumene subtype, an example of the LCT (lithium, cesium, tantalum) family. It is one of a group of beryl- and complex-type pegmatites exposed along the Uchi–English River subprovincial boundary-zone, Ontario, in the Superior Province of the Canadian Shield. The mineral assemblage containing zoned "fluor-elbaite"�liddicoatite crystals was the last product of primary, near-solidus crystallization of the pegmatite and is unique not only to this subprovincial boundary, but also throughout the vast number of rare-element pegmatites distributed across Ontario. The most calcic composition of liddicoatite analyzed here corresponds to (Ca0.5Na0.40.1) (Li1.5Al1.2Mn0.2Fe0.1) Al6(Si6O18) (BO3)3 (OH3.4F0.6). Other calcium-enriched species found in the McCombe pegmatite include microlite (Ca1.2Na0.60.2)(Ta1.6Nb0.3Sn0.1)O6(F0.7OH0.3), Ca-enriched almandine (Alm44.6Sps26.4Grs26.2), Ca-enriched spessartine (Sps69.3Alm19.8Grs10.9), and fluorapatite. Evidence from progressively evolved units of the pegmatite and mineral zonation shows that contamination of the pegmatite-forming melt occurred, and that fluids from the pegmatite migrated out into the mafic metavolcanic host-rocks, creating a Li-, Cs-, and B-enriched metasomatic aureole. The evolution of the pegmatite-forming melt resulted in increased activity of fluorine, and the essentially in situ fractionation of the contaminated melt led to the crystallization of the rare-element-enriched minerals. Patterns of zonation seen in back-scattered-electron images show that primary crystallization of columbite–tantalite, garnet and tourmaline species involved multiple episodes of growth and dissolution in a dynamic system. Liddicoatite was able to form, not because of any one of these processes, but because they all acted together to concentrate both Li and Ca, a sequence of events that is apparently very rare in nature
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Project Unit 98-001. Time-scales of formation of rare-metal class pegmatites and associated peraluminous granite in the Superior Province of Ontario
Abstract not available
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Electron microprobe compositions of tantalum-bearing oxides and potassium feldspar from rare-element granitic pegmatites, Superior Province, northwestern Ontario
Abstract not available