Nepheline syenite and syenite gneisses crop out in a 6 kilometre band on the southern blank of Mount Copeland, 15 kilometres northwest of Revelstoke. The rock consists of orthoclase with subordinate nepheline and albite and small amounts of amphibole, pyroxene and magnetite. It has a banded texture and contains both fine and coarse- grained zones. The Mount Copeland syenites are exposed in a large antiformal structure and have been subjected to more than one phase of folding. The contacts appear gradational. Three main alkaline rock units have been defined; a basal nepheline syenite gneiss, overlain by alkaline amphibolite, which is in turn overlain by calcareous and saturated syenites. The alkaline rocks intrude micaceous quartzites and calcsilicate gneisses of the Frenchman Cap autochthonous cover sequence. The metasedimentary succession has been correlated with a similar succession in the Perry River and Mount Grace areas. Based on these correlations, it appears that the gneisses at Mount Copeland lie stratigraphically beneath the Mount Grace extrusive carbonatite.
Thirty-four samples collected from the deposit were analysed with the following results:
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Major oxides Weight (per cent)
SiO2 51.30 - 61.26
Al2O3 17.27 - 24.38
Fe2O3 0.84 - 8.21
CaO 0.04 - 9.61
Na2O 2.74 - 8.76
K2O 7.49 - 10.14
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These analyses indicate the rocks are a potential source of
feldspathic material although most samples are high in iron. To
better evaluate the material, two 20 kilogram samples, low in iron,
were sent to CANMET for processing. At CANMET they were crushed, run
through a dry magnetic separator (-10 + 100 mesh) and a mica-iron
float produced with the following results:
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Magnetic Separation (Weight, per cent) Magnetic Nonmagnetic -100 Mesh Sample 1 40.0 51.0 9.0 Sample 2 23.4 66.3 10.3
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Flotation Concentrate/float tails
(Weight, per cent) Slimes Mica-Iron Magnetic Nonmagnetic
Sample 1 15.6 27.9 19.1 36.5
Sample 2 20.0 3.8 28.6 46.6
The nonmagnetic concentrates were then analysed with the
following results:
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Major oxides Separation Floatation (Weight, per cent) 1 2 1 2 SiO2 56.20 47.1 54.80 50.70 Al2O3 19.20 20.50 18.30 21.10 Fe2O3 0.50 1.23 0.19 0.41 CaO 1.27 1.60 0.98 0.80 Na2O 6.58 6.02 6.44 5.48 K2O 8.40 9.45 8.76 10.57
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Full liberation is achieved at less than 100 mesh. Samples
processed by CANMET contain high levels or iron and titanium which
could not be reduced below 0.19 per cent and 0.40 per cent
respectively. This makes it difficult to produce nepheline syenite
meeting market specifications.
