The Fir occurrence is located approximately 26 kilometres northeast of Blue River in the North Thompson River Valley. The showing is 1.25 kilometres north of the Bone Creek carbonatite occurrence (083D 036) and is accessed by a logging road that intersects Highway 5 approximately 23 kilometres north of Blue River.
Carbonatite consisting of beforsite and lesser sovite occurs as sills within quartz-hornblende-mica schist of the Semipelite-Amphibolite division of the Hadrynian Horsethief Creek Group. Other lithologies within the area include amphibole biotite schist, biotite muscovite gneiss and amphibole-biotite-garnet gneiss. In British Columbia, carbonatites are found in a broad zone parallel to and encompassing the Rocky Mountain Trench, extending from the Elkford area northward to Williston Lake. Occurrences within this belt have been subdivided into three sub-belts. Most carbonatite occurrences are found in the central belt, which is predominantly within the Omineca Belt of the Canadian Cordillera and hosts most known stratiform carbonatites in the area between Revelstoke and Valemount. Within this northwest-trending belt, a number of carbonatite layers containing anomalous strontium, niobium, tantalum and rare earth elements occur within the Semipelite-Amphibolite division of the Hadrynian Horsethief Creek Group in the Monashee Mountains near Blue River (Fieldwork 1984). All of these carbonatites have sodic pyroxene and amphibole-rich fenitic margins and are associated with nepheline and sodalite syenites, urtites to meltergites. The time of emplacement of these carbonatites appears to be prior to the deformation and metamorphism associated with the Jura-Cretaceous Columbian orogeny and, in part, related to extension and/or rifting along the western continental margin. A third major extensional event at the end of the Devonian (circa 350 Ma) resulted in the intrusion of carbonatites. Carbonatites and surrounding metasedimentary rocks have been regionally metamorphosed to upper amphibolite grade (kyanite to sillimanite zone; Open File 1987-17; Bulletin 88).
The Fir carbonatite likely strikes 400 metres in a northerly direction. It consists of two subparallel beforsite sills. The lower sill is between 26 and 50 metres thick and the upper sill is 22 metres thick. A 2-metre exposure of beforsite was located 400 metres north of the Discovery outcrops.
Beforsite outcrops are coarsely crystalline and typically weather white. Accessory minerals in the carbonatites include apatite, amphibole, olivine, magnetite, pyrite, pyrrhotite, pyrochlore and columbite. Beforsite is almost void of biotite and magnetite. Three distinct textures were observed: breccias composed of tightly packed dolomite fragments within a finely crystalline dolomite groundmass; a porphyritic texture with ghost dolomitic crystals in a fine-grained matrix; and massive beforsite with local banding of accessory minerals.
The porphyritic textures appear to have developed from resorption of beforsite crystals into a fine grained beforsite matrix. The textural variability of the beforsite and the differences in the niobium to tantalum ratios indicate formation from a series of magma pulses similar to the Verity occurrence (083D 005).
The Fir carbonatite consists almost entirely of beforsite cut by segregated layers of amphibole and cemented mylonite. Beforsite units have the highest background niobium and tantalum values of all carbonatites in the area. Tantalum averages were greater than 0.015 per cent (Assessment Report 10274). Sampling of the Discovery outcrops yielded assays of 1.02 per cent niobium, 0.06 per cent tantalum and 6.31 per cent phosphate (Assessment Report 9566). A sample from drillcore yielded values of 0.18 per cent tantalum and 8.51 per cent phosphate (Assessment Report 9923). Niobium-tantalum minerals identified in carbonatites found in the Blue River area include pyrochlore, ferrocolumbite and minor fersmite.
The Upper Fir carbonatite, located to the southeast of the original Fir carbonatite, consists of two or more major and several minor isoclinally folded, subparallel carbonatite sills varying in thickness from 6.2 to 110.53 metres and dipping 5 to 10 degrees north-northwest. Extensive drilling and trenching has defined the known extent of the Upper Fir as 1450 metres north to south and 800 metres east to west. The Upper Fir thins toward the north and is cut in the south and east by a west dipping, recemented shear zone. Folding has caused substantial thickening of the unit at the fold hinges. The sills are hosted in metapelites that dip up to 10 degrees to the southeast. Mineralization is similar to the Fir carbonatite, with beforsite as the dominant carbonatite type. Sovites occur as minor layers up to a few metres in thickness either within the beforsite or at the country rock contacts.
Approximately 200 metres from the Fir carbonatite layer, the Bone carbonatite, approximately 5 metres thick and extending for approximately 2 kilometres along strike, is composed of apatite beforsite with coarse pyrochlore and only minor ferrocolumbite. Most of the pyrochlore is dark to black and contains uranium and tantalum in the greatest concentration in the camp (Exploration and Mining in British Columbia 2001).
The Blue River area was originally staked in 1950 for vermiculite by O.E. French, a homesteader in the area. Later investigations by French resulted in the discovery of the pyrochlore-bearing carbonatites. In 1952, St. Eugene Mining Corporation Ltd. optioned the property and additional claims were staked. Most of the exploration work, consisting of trenching, sampling and blasting, was confined to the Verity and Mill claims. The property was dropped by St. Eugene and remained idle until June 1976, when J. Kruszewski restaked the area. In June 1978, another trenching and sampling program was conducted under the supervision of E. Myers of Calgary, Alberta, with Kruszewski's assistance. A total of 840 cubic metres of stripping was undertaken and two grab samples were taken. In 1979, Kruszewski was approached by Anschutz (Canada) Mining Ltd. and an option contract was signed in February 1980. In 1981 and 1982, the company conducted geological mapping, drilling and sampling on the Bone Creek, Fir, Mill and Verity carbonatites.
Commerce Resources Corporation acquired the claims in 2000 and carried out limited mapping, sampling and geochemical analyses. In 2001, Commerce Resources undertook an exploration program that included geological mapping, geochemical sampling, drilling six HQ-size diamond-drill holes totalling 1245.32 metres, and completing 10.36 kilometres of grid lines and 8.55 kilometres of ground magnetometer surveying. Soil sampling proved to be a successful method of detecting buried carbonatite bodies. In 2002, the Fir property was grouped together with the company’s other carbonatite projects in the area to form the Blue River property. That same year, exploration on the Fir carbonatite included the drilling of five HQ-size diamond-drill holes totalling 898.47 metres, prospecting and rock and stream sediment sampling. This work led to the discovery of the Upper Fir carbonatite showing to the east of the original Fir carbonatite.
In 2003, metallurgical testing was carried out on material extracted from the Fir carbonatite in addition to a limited prospecting and soil sampling program. Eight HQ-size diamond-drill holes totalling 810 metres were drilled in 2005, mostly targeting the Upper Fir showing. Work continued with a focus on the Upper Fir showing in 2006 with geochemical sampling, ground geophysics, prospecting, trenching, structural mapping and drilling 17 HQ-size diamond-drill holes totalling 3021 metres. In 2002, Commerce Resources released an estimate for a potentially open pit minable inferred resource of 5.2 million tonnes grading 194 grams per tonne tantalum, 897 grams per tonne niobium and 3.5 per cent phosphate using a cutoff grade of 150 grams per tonne tantalum (Press Release - Commerce Resources Corporation, June 5, 2002). Commerce Resources released another resource estimate in March 2003 based on five holes drilled in 2002, six drilled in 2001 and four drilled in 1981. The indicated resource was 5,650,000 tonnes grading 203.1 grams per tonne tantalum and 1047 grams per tonne niobium, and the inferred resource was 6,746,000 tonnes grading 203.1 grams per tonne tantalum and 1047 grams per tonne niobium (Press Release - Commerce Resources Corporation, March 10, 2003).
Exploration continued in 2007 with a focus on the Upper Fir carbonatite. The program consisted of prospecting, geochemical sampling, mapping, geophysical surveying and drilling 20 HQ-size diamond-drill holes totalling 4710 metres. Eighteen of the holes, totalling 4310 metres, were drilled around the Upper Fir. All 18 holes in the Upper Fir intersected carbonatite units varying in thickness from 8.77 to 95.7 metres. Assays returned maximum grades of 693 grams per tonne tantalum and 9142 grams per tonne niobium. The southernmost hole drilled on the Upper Fir across a 17.04-metre long section averaged 153 grams per tonne tantalum, 4943 grams per tonne niobium and 2.21 per cent phosphate, and an 11-metre long section averaged 329 grams per tonne tantalum, 4990 grams per tonne niobium and 2.83 per cent phosphate (Assessment Report 30011). Using a cut-off grade of 150 grams per tonne, indicated and inferred resources were estimated at 8.6 million tonnes averaging 208.9 grams per tonne tantalum and 1372.06 grams per tonne niobium, and 5.5 million tonnes averaging 208.2 grams per tonne tantalum and 1349.9 grams per tonne niobium, respectively (Assessment Report 30011). In 2009, 30 HQ-size diamond-drill holes were completed, totalling 5586.6 metres. Of the 22 drillholes drilled on the Upper Fir, 19 holes intersected carbonatite. Additional work included geochemical sampling, geophysical surveying, trenching, metallurgical testing and structural mapping. The following year, exploration focused solely on the Upper Fir carbonatite with the intention of better defining the grades, mineralization, structure and extent of the deposit. In all, 54 HQ-size diamond-drill holes were completed, totalling 12,949.34 metres. Six holes were oriented-core drillholes and six holes were subject to downhole geophysical surveys. Infill drilling continued in 2011 with 34 diamond-drill holes totalling 8715 metres.
Commerce Resources released a National Instrument (NI) 43-101 compliant technical report dated January 31, 2011 in February 2011. The report included an updated resource estimate (www.sedar.com)
----------------------------------------------------------------------------------------Classification Amount (tonnes) Ta2O5 (%) Nb2O5 (%) Indicated 36,350,000 0.0195 0.17 Inferred 6,400,000 0.0199 0.189 ---------------------------------------------------------------------------------------- |
A positive NI 43-101 preliminary economic assessment on the rare metal development potential of the property was completed in November 2011. It indicated the deposit could be economically developed as an underground mine and recommended future studies to support a prefeasibility level of assessment. Effective June 22, 2012, the NI 43-101 report on mineral resource update reported an indicated resource of 51.8 million tonnes grading 192 grams per tonne tantalum and 1490 grams per tonne niobium, and an inferred resource of 8.8 million tonnes grading 186 grams per tonne tantalum and 1660 grams per tonne niobium (Press Release - Commerce Resources Corporation, July 6, 2012; Postolski et al., 2012).
In June 2013, a NI 43-101 report on mineral resource update reported an indicated resource of 48.4 million tonnes grading 197 grams per tonne tantalum and 1610 grams per tonne niobium, and an inferred resource of 5.4 million tonnes grading 191 grams per tonne tantalum and 1760 grams per tonne niobium (Kulla, G., Postolski, T. (2013-06-21): NI 43-101 Technical Report on Mineral Resource Update - Blue River Tantalum–Niobium Project).
In 2017, Commerce Resources signed a memorandum of understanding for delivery of a 1-tonne sample from the Upper Fir deposit to an Estonian metallurgist to test his proprietary process for separation of niobium and tantalum (Information Circular 2018-1).
