The Phoenix Tailings property is centred approximately 7 kilometres east of Greenwood, B.C. It is composed of two non contiguous blocks that cover a total area of 413 hectares and encompass three separate tailings sites.
The area is situated within Quesnellia, a terrane that accreted to North America during the Middle Jurassic. Proterozoic to Paleozoic North American basement rocks are exposed in the Kettle and Okanagan metamorphic core complexes. These core complexes were uplifted during the Eocene, and are separated from the younger overlying rocks by low-angle normal faults. The distribution of these younger rocks is largely controlled by a series of faults, including thrust faults (related to the accretionary event), and Tertiary extensional faults.
The oldest of the accreted rocks in the Greenwood area are Late Paleozoic volcanics and sediments. These rocks are separated into the Knob Hill Complex and overlying Attwood Formation. Rocks of the Knob Hill Complex are of dominantly volcanic affinity and consist mainly of chert, greenstone and related intrusives, and serpentinite. The serpentinite bodies of the Knob Hill Complex represent part of a disrupted ophiolite suite that has since been structurally emplaced along Jurassic thrust faults. Commonly, these serpentinite bodies have undergone iron-carbonate alteration to listwanite, as a result of the thrusting event. Locally, sediments and volcanics (largely argillite, siltstone, limestone and andesite) of the Late Paleozoic Attwood Formation unconformably overlie the rocks of the Knob Hill Complex.
The tailings themselves consist of fine, sand-sized waste product of crushed and processed ore from the Phoenix copper-gold skarn deposit. Mineralogical studies of the Tremblay tailings show that the tailings are composed dominantly of quartz (34 per cent), calcite (31 per cent) and chlorite (18 per cent), with lesser magnetite (5 per cent), illite (3.5 per cent), grossular to andradite garnet (3 per cent) and epidote. Minor amounts of hematite, pyrite, chalcopyrite, apatite, goethite, ilmenite and zircon are also present, with trace amounts of native gold.
The tailings on the property are the byproduct of historic open-pit mining and milling at the Phoenix copper-gold skarn deposit. The Phoenix mine was operated by Granby Mining as a (primarily) underground, direct smelting operation from 1900 to 1919, then as an open-pit mine from 1956 to 1978. Milling operations, from which the tailings were generated, started in 1959 and continued without interruption until 1978. Historical production records indicate that approximately 13.2 million tonnes of tailings were produced during the operation (Assessment Report 25364).
Historical records indicate that from 1959 to 1967, 4.19 million tonnes of tailings, grading 0.15 per cent copper, 0.38 gram per tonne gold and 3.8 grams per tonne silver, were discharged to the Tremblay site. From 1967 to 1976, 7.33 million tonnes of tailings with an average grade of 0.08 per cent copper, 0.31 gram per tonne gold and 3.1 grams per tonne silver were discharged to the Twin Creek site. In the final years of operation, when mining had ceased from the Phoenix pit but milling of stockpiled ore (plus ore from other sites) was ongoing, tailings were discharged into the pit. Historical records indicate that the Phoenix pit site contains 1.64 million tonnes of tailings grading 0.09 per cent copper, 0.17 gram per tonne gold and 2.23 grams per tonne silver (Assessment Report 25364).
In 1985, Kettle River Resources Ltd. and Noranda Explorations Company Limited began a program to evaluate grade and recovery methods on 4 145 835 tonnes of tailings from past production of the Phoenix pit (082ESE020).
In 1995, with support from the Explore BC. Program, Kettle River Resources Ltd. carried out a limited program of sonic drilling and sampling of the Phoenix mine tailings to assess their gold content and to determine the economics of re-processing. In total, 42 metres of drilling was completed in two fully sampled holes. The gold content was found to be 20 per cent lower than previously reported. Metallurgical studies on the sampled material determined that re-grinding and cleaner flotation would produce a concentrate grading of approximately 18 per cent copper and 207 grams per tonne gold (Assessment Report 25364).
In 2002, Kettle River Resources commissioned the Centre for Industrial Minerals
Innovations at the University of British Columbia to conduct further testing on the Tremblay tailings. The study was directed primarily at the feasibility of magnetite production. Testing showed that re-grinding and three stages of cleaner magnetite separation were required to produce a marketable product with 96.1 per cent magnetite (Assessment Report 26965A).
In 2011, Kettle River Resources commissioned an informal study of the economical viability of a gold-only reprocessing operation at the Tremblay and Twin Creek tailings sites. The study assumed head gold grades and tonnages indicated by historical mining records. Historical metallurgical test work was used for project design and recovery estimates. The study concluded that, based on preliminary investigations, a gold recovery operation that involved regrinding and froth flotation of the Tremblay and Twin Creek tailings at a rate of 10 000 tonnes per day might be economically viable (Kettle River Resources, News Release, August 1, 2012).
