The Mount Kruger prospect is located 2.5 kilometres west of Kilpoola Lake, 10 kilometres west of Osoyoos. The NEP claims, covering this deposit, were originally staked in 1962 as the Buck claims.
The Mount Kruger occurrence was staked in 1963 as the Buck 1-3 claims by K. Butler. Nepheline syenite was sampled and analysed by British Columbia Research Council and International Minerals and Chemical Corp. Beneficiation methods were tested by Minerals Resource Branch. The claims lapsed in 1971. In 1974, Bethlehem Copper Corp. staked the property as the Buck 1-4 claims. Pits were blasted and sampled for chemical analyses and a metallurgical study. The claims lapsed again and restaked in 1984 by D. Atkinson. In the following year the NEP claims were staked by W. Bonin and later in that year transferred to Okanagan Nepheline.
Regionally, the Mount Kruger prospect is underlain by the Jurassic Kruger syenite. The main outcrops of the Kruger syenite form a near-rectangular mass 11.4 by 3.3 kilometres along the edge of the Middle Jurassic Similkameen batholith with small lenticulars to the south and northwest. The Kruger syenite and Similkameen batholith intrude north-striking and moderately west dipping Carboniferous to Permian Kobau Group metavolcanic and metasedimentary rocks. The Kobau Group consists of siliceous and cherty metasediments and metamorphosed intermediate to mafic volcanic rocks. No pronounced contact effects are evident in the Kobau Group, although hornfelsed blocks are occasionally seen in syenite and veins of syenite occur in wall rocks. Agmatite of syenite in an aplite matrix have been found at least one location along the Kruger-Similkameen intrusions. Elsewhere the contact appears gradational.
The pluton shows a moderately developed zonal structure, with melanocratic syenite or diorite most common in the southwestern portion adjacent to the Similkameen batholith. Melanocratic rocks contain augite, locally forming pyroxenite which is characteristically armoured by hastingsite. More leucocratic and nepheline-rich varieties occur mainly near Kobau Group rocks to the northwest. These rocks contain hastingsite and biotite as the mafic minerals. The zonation is rather weak however, as melanocratic, nepheline poor syenite tends to form a matrix for other phases. Microcline, occasionally perthitic, is the only feldspar found in abundance. All phases show a moderately strong trachytoid foliation parallel to contacts. Nepheline occurs as euhedral phenocrysts and is strongly altered to natrolite and sericite. Garnet is present in all the rocks. The nepheline syenite phase has a high iron content, present mainly as very fine-grained (-200 mesh) disseminated magnetite.
The occurrence is comprised of nepheline syenite and syenite that forms massive sills in Kobau Group rocks. Later intrusions are composed of diorite (lesser gabbro) and quartz monzonite. The Kobau Group rocks exhibit moderate contact metasomatism or metamorphism along its borders with the intrusive rocks.
The nepheline syenite and syenite is dominantly potassium feldspar porphyritic and forms sills conformable to foliation in the Kobau Group. All units show penetrative foliation striking north and dipping moderately west. In the sills are several zones of moderate to intense cataclastic deformation in which originally coarser grained rocks are smeared along foliation planes and coarse crystals are deformed and partly recrystallized to extremely fine-grained aggregates. Within the sills are discrete lenses of Kobau Group rocks and mafic dikes.
The nepheline syenite contains three mineralogical zones based on mafic mineral content. The zones are defined as:
--------------------------------------------------------------------1. Hornblende zone - abundant hornblende, porphyroblasts of almandite, minor aegirine-augite, biotite, granular aggregates of grossularite-almandite-andradite 2. Aegirine-augite zone - moderately abundant aegirine-augite mainly in cores of mafic clots, moderately abundant hornblende, biotite and almandite-andradite 3. Biotite zone - abundant biotite, almandite-andradite, lesser hornblende, minor aegirine-augite. --------------------------------------------------------------------- |
The composition of each zone determined from the modal analysis of 53 polished thin sections is as follows in weight per cent (Assessment Report 15783):
----------------------------------- ZONE Hornblende Aegirine- Biotite Augite SiO2 59.6 58.7 58.5 Al2O3 21.0 20.4 20.1 Fe2O3 3.0 4.0 4.0 MgO 0.26 0.68 0.74 CaO 1.0 2.2 1.3 Na2O 3.6 3.3 3.3 K2O 11.6 10.9 11.4 TiO2 0.15 0.20 0.33 H2O 0.12 0.22 14.7 ----------------------------------- |
The margins of the sills are commonly much finer grained than the cores but have a lower mafic mineral content. Generally, the nepheline syenite has a low alumina and high alkali and iron content.
Three samples of a salic light coloured phase analysed as follows in weight per cent (Fieldwork 1988, page 486):
--------------------------------- SiO2 49.55 to 74.04 Al2O3 14.27 to 15.13 Fe2O3 0.65 to 11.33 CaO 0.87 to 9.16 Na2O 2.91 to 3.86 K2O 4.68 to 5.91 --------------------------------- |
The nepheline syenite comprises two large sills (Main and East) and two much smaller sills (South and Northwest). The Main sill is 340 by 160 by 80 metres and contains an inferred reserve of 11.5 million tonnes of nepheline syenite. The southern half of the East sill is 700 by 120 by 60 metres and has an inferred reserve of 13.2 million tonnes of nepheline syenite. Using a 20 per cent dilution factor, overall inferred reserves for the Main and East sills are 20 million tonnes of nepheline syenite (Assessment Report 15783).
Analyses of three samples collected from outcrop of a salic, light-coloured phase exposed on a hilltop west of Kruger Mountain, approximately 9 kilometres west of the town of Osoyoos, indicate low alumina (up to 13.2 per cent) and high iron content, indicating the rock has limited potential to meet commercial specifications for glass and ceramic applications (Fieldwork, 1988).
