Projects in the Pipeline: Speciality metals in Canada

• Localización: Industrial Minerals, ISSN 0019-8544, Nº. 545, 2013
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • Alkaline intrusions are characterised by their content of feldspathoids, alkali amphiboles and pyroxenes (S ?rensen, 1986). Based on molar ratios of [Na 2 O + K 2 O] relative to Al 2 O 3, they are classified as metaluminous or peralkaline. In peralkaline intusions Na 2 O + K 2 O >Al 2 O 3 (Marks et al. 2011). Peralkaline intrusions are described as agpaitic if their agpaitic index ((Na + K) / Al) is greater than unity (Salvi and Williams-Jones, 2004). As with carbonatites, some peralkaline intrusions, especially those of agpaitic type, contain large resources of SMs, although the ore mineralogy and chemistry differ significantly from carbonatites. Peralkaline intrusion-associated deposits contain Zr, Nb, Ta, Y, HREEs, Th and Be (Richardson and [Birkett], 1996c). The REE mineralisation in these deposits displays relatively flat chondrite-normalised patterns and may have negative Eu anomalies, as exemplified by deposits from the Nechalacho project near Thor Lake in the Northwest Territories (Williams-Jones, 2010), the Strange Lake Complex on the border of Quebec and Labrador ([Andy Kerr], 2011) and the Kipawa area of Quebec (Constantin, 2010; Constantin and Fleury, 2011).

    REE +/- P veins ([Hoidas] type) In Canada, multiple LREE-enriched alkaline veins or dykes are in the Churchill Province in Saskatchewan. They were emplaced in shear zones superimposed on deep-seated crustal discontinuities (Rogers, 2011), such as the Hoidas-Nisikkatch fault ([Charles Normand] et al., 2009). [REEs] are contained largely in fluorapatite and allanite-Ce. Monazite, bastnaesite and chevkinite are minor constituents (Halpin, 2010), and Ba-rich feldspar is commonly associated with mineralisation. The veins are predominantly enriched in La, Ce, and Nd. Mineralisation is complex, with the chemical and mineralogical compositions changing with each vein generation. Based on high concentrations of REE, plus a relative depletion in high field strength elements, Halpin (2010) indicates that these occurrences may be alkaline intrusion- or carbonatite-related. The JAK Zone at Hoidas Lake is the best- documented Canadian example (Normand et al., 2009). Drilling has defined the deposit over 750 metres along strike, to a depth of 150 metres (Rogers, 2011). Based on a 1.5% total REE cut-off grade, a recent ore estimate (including measured, indicated and inferred) is 2,847,000 tonnes grading approximately 2% total REE (Great Western Minerals Group Ltd., 2011a). Other styles of monazite- and allanite-bearing mineralisation in the same general area are described by Normand (2010, 2011).

    Sedimentary phosphate deposits contain significant concentrations of lanthanides and Y ([George J. Simandl] et al., 2012). In British Columbia, some upwelling-type phosphate deposits (Simandl et al. 2011a, b) contain significant quantities of REEs (Pell, 1994; Simandl et al., 2012). Summaries of sedimentary phosphate deposits and their REE contents in British Columbia are provided by Pell (1991), Butrenchuk (1996), and Simandl et al. (2011a, b, c). The Fernie Formation in southern British Columbia and the Whistler Member of the Sulphur Mountain Formation in northeastern British Columbia are two of the more promising geological units for REE. Phosphate deposits in Alberta are described by MacDonald (1987); those in the Athabasca Basin in Saskatchewan by Ramaekers (1979, 1980, 1981).