The Kutcho Creek deposit is located around Sumac Creek, 7 kilometres east of Kutcho Creek and 100 kilometres southeast of Dease Lake.
In 1972 and 1973 respectively, Sumac Mines Ltd. and Esso Minerals of Canada independently located and staked the ground covering the Kutcho Creek polymetallic volcanogenic massive sulphide deposits. Drilling and underground development work resulted in Esso owning the east end of the outcropping Kutcho deposit (lens) and the deep Esso West deposit (lens). Sumac ground covered the down plunge western portion of the Kutcho deposit and the Sumac deposit (lens).
The deposits are in the Kutcho Formation of the Upper Permian-Lower Triassic Cache Creek Complex (Geological Survey of Canada Paper 86-16) which underlies carbonates and sedimentary rocks interpreted to correlate with the Upper Triassic Sinwa Formation limestone and the Lower Jurassic Inklin Formation, respectively. The Kutcho deposits occur within the upper felsic, largely fragmental volcanic cycle of the Kutcho Formation. New dating by the Mineral Deposits Research Unit (MDRU) at the University of British Columbia yielded ages of 242 to 245 Ma for the hostrocks (F. Child, personal communication, 1995). The Kutcho Formation was previously thought to be Upper Triassic (Geological Survey of Canada Open File 2779) but this new dating places the age at the Permian-Triassic boundary. The Sinwa Formation has recently been reassigned to the Stuhini Group (Stikine Terrane), and the Inklin Formation to the Laberge Group (Overlap Assemblage) (M. Mihalynuk, personal communication, 1996). The area of the deposit is interpreted to have been isoclinally folded during formation of the King Salmon allochthon in Early to Middle Jurassic time.
The interpreted stratigraphic sequence consists of a 2000 metre or more lower unit dominated by mafic flows and tuffs with local dacite to rhyolite flows and tuffs and argillite layers. This sequence is cut by an elongated body of trondhjemite that is quartz rich and perhaps the source of the quartz crystals in the fragmental volcanic rocks that occur higher in the section. Above is the footwall unit, some 300 metres of largely lapilli tuff. The massive sulphide lenses occur where this unit gives way to lapilli crystal tuff and laterally correlative quartz-feldspar crystal tuff that are interlayered with or cut by mafic plagioclase porphyry (locally called gabbro). Above the hangingwall unit is a series of tuffs and argillites that are cut by mafic sills, then a volcanic conglomerate unit that underlies the apparent Sinwa carbonates and Inklin sediments.
The Kutcho assemblage consists of bimodal, calcalkaline basaltic andesite or basalt and rhyodacite or rhyolite. It is generally in fault contact with rocks of the Carboniferous-Jurassic Cache Creek Complex but may have a Cache Creek basement. The assemblage occurs within the fault-bounded King Salmon allochthon. Movement on the faults was probably Early to Middle Jurassic, but uplift continued into the Late Jurassic. Rocks within the allochthon were regionally metamorphosed to greenschist facies and deformed at that time. The sequence is interpreted to be folded, and small-scale reverse faults are common in the underground workings.
In the hangingwall of the mineralized zone, shoshonitic mafic plagioclase porphyry cuts the country rock. The porphyry locally exhibits peperite structures with sedimentary units in the Kutcho assemblage (J. Thompson, personal communication, 1995), so is apparently very close in age (syn-mineral?). The porphyry is extensively altered to chlorite and epidote. Bridge et al. concluded that the massive sulphide deposits occur at a facies change from quartz feldspar crystal tuff to lapilli crystal tuff (CIM Special Volume 37 (1986)).
Schistose quartz-eye feldspar-grain rock with scattered pyrite cubes is the dominant hangingwall lithology. The unit contains scattered clasts on the ridge above the exploration adit but is clearly fragmental with small to large lapilli to blocks of quartz feldspar porphyry, fine grained to quartz porphyritic partially flatted pumice fragments and some more exotic, calcareous, mafic-looking clasts. Geochemistry by MDRU shows this unit to be a primitive, tholeiitic rhyolite with SiO2 near 70 per cent. It is Na2O-rich and has relatively low values in zirconium, yttrium and uranium (like rhyolites in Iceland).
In the footwall sequence, on Imperial Ridge, above the adit, a foliated quartz feldspar-bearing zone underlies the massive sulphide zone. Quartz tends to be finer grained than in the hangingwall. Deeper in the footwall, variably altered feldspar phyric rocks dominate but zones with coarse quartz eyes occur locally. Below the footwall alteration is a monotonous assemblage of these rocks, then a zone with occasional thin layers of pale green to white, very fine dust to fine crystal tuffs with sericite partings. A small lens of impure marble had minor associated pyrite and chalcopyrite mineralization. The sequence is interpreted to consist largely of crystal to lapilli tuffs, and the correlative, less altered rocks on Sumac Ridge to the west are clearly fragmental volcanic rocks. On Sumac Ridge, the footwall sequence has many more coarse quartz-rich zones. The quartz and feldspar-dominated sequences are gradational over hundreds of metres of section. The feldspar-dominated section on Sumac Ridge is underlain by chlorite schists, interpreted to be derived from basalt, with local fine-grained sedimentary layers. Geochemistry by MDRU indicates that the basalts are tholeiitic.
The trondhjemite is locally brecciated and foliated at its margins. In the west, it consists of medium-grained quartz, plagioclase and chloritized mafics. In the southeast, it is coarse grained and porphyritic with quartz grains to 1 centimetre in size. The coarser variety is more calcic, akin to tonalite rather than the more sodic trondhjemite (Fieldwork 1977).
In the mineralized interval on surface, the hostrock is strongly altered sericite schist with pyrite cubes and dolomite grains but no obvious mineralization. Locally, quartz eyes are still visible, and fragments are seen locally in drill core. The mineralized zone has an altered footwall sequence some 300 metres thick, and a less intense, thinner zone above. Geochemically, sodium is depleted, and potassium is enriched near the mineral lenses. In the footwall, this alteration extends for about 500 metres laterally and nearly 300 metres below the lenses; in the hangingwall, it extends 100 metres laterally and about 180 metres above the mineralized lenses. In the alteration halo, calcium and magnesium are also enriched and silica values are relatively elevated. The footwall zone is pyritic, both as stringers and disseminations, and has abundant disseminated dolomite. Individual deposits are stratabound and lenticular; they pinch out to the south updip but interdigitate with the country rock downdip to the north. All are at the same relative stratigraphic position, but individual lenses are en echelon and separated by about 300 metres. They strike about 280 degrees and dip north at 40 to 45 degrees (CIM Special Volume 37 (1986)).
Mineralization occurs in three areas along 3.5 kilometres (CIM Special Volume 37, 1986) of a zone that extends for about 15 kilometres (Fieldwork 1975). Intense footwall alteration and a footwall pyrite zone are developed throughout the zone. Metallic minerals occur in a series of massive sulphide layers and include pyrite, sphalerite, chalcopyrite, bornite, minor chalcocite, trace tennantite, galena, digenite, djurleite and idaite. Schistose partings occur locally in the massive sulphide zone exposed in the adit. Whether this represents pulses of mineralization or structural repetition is not clear. Metal zoning occurs laterally in the ore lenses with copper-rich cores and zinc-rich peripheries but is not evident vertically within the lenses. Non-sulphide gangue includes dolomite, quartz and sericite.
In 2019, Kutcho Copper reported four targets exist on the Kutcho project that are located between, below or along strike from existing mineral resources and represent high probability drill areas: 1) The Main-Sumac Gap identifies a 400 metre by 380 metre panel between the Main and Sumac lenses that is untested by drilling. A conductive geophysical anomaly coincides with the area and is 360 metres long; 2) Significant portions of all three lenses remain open down dip outside of current resources; 3) The Esso-West Expansion target lies 300 metres west of the Esso deposit where a 150 metre by 1500 metre long geophysical anomaly has been drill tested yielding several mineralized intercepts including 7.2 metres of 2.0 per cent of copper, 5.2 per cent zinc and about 17 grams per tonne silver in hole E094B3 (Kutcho Copper Corp., News Release, March 4, 2019). There also remains 300 metres of untested Kutcho horizon between hole E094B3 and Esso, along with an additional 1000 m of untested horizon to the west of hole E094B3; and 4) The Footwall Zone (FWZ) lies beneath the Main zone and represents a stacked massive sulphide horizon that is open in all directions. The last drill hole to the east and down dip intersected 1.5 metres of 3.54 per cent copper, 6.94 per cent zinc, 316.9 grams per tonne silver and 1.47 grams per tonne gold in hole E057 (Kutcho Copper Corp., News Release, March 4, 2019).
Between 1973 and 1984, development work was carried out independently but cooperatively by Sumac Mines Ltd., (controlled by Sumitomo Metal Mining Co. Ltd.) and Esso Minerals of Canada (Imperial Oil Ltd.). Greater than 50,000 metres of drilling was completed, and a 218-metre crosscut producing greater than 3000 tonnes of ore for bulk sampling was excavated. This work resulted in Esso owning the east end of the outcropping Kutcho deposit (lens) and the deep Esso West deposit (lens). Sumac ground covered the down plunge western portion of the Kutcho deposit and the Sumac deposit (lens).
Further work was done between 1985 and 1987, apparently concentrating on exploration outside the main deposit area. Reserves for the three zones were: Kutcho - 17 million tonnes grading 1.62 per cent copper, 2.32 per cent zinc, 29.2 grams per tonne silver and 0.39 gram per tonne gold; Sumac - approximately 10 million tonnes grading 1.0 per cent copper and 1.2 per cent zinc; and Esso West - about 1 to 1.5 million tonnes of approximately double Kutcho grades (CIM Special Volume 37 (1986), page 122).
In early 1989, Esso Minerals sold its portion of the property to Homestake Mining (Canada) Limited who subsequently sold a minority interest to American Reserve Mining Corp.
An "underground mineable reserve" was reported in 1991 for the Kutcho lens as 11.6 million tonnes grading 1.67 per cent copper, 2.30 per cent zinc, 32.7 grams per tonne silver and 0.36 gram per tonne gold; and for the Esso West lens as 2.7 million tonnes grading 2.14 per cent copper, 3.61 per cent zinc, 44.9 grams per tonne silver and 0.40 gram per tonne gold (George Cross News Letter No.54 (March 18) 1991).
The property was optioned to Teck-Cominco Metals Ltd. in 1992. Teck-Cominco carried out deep penetration EM geophysical surveys (UTEM) over the Esso zone with the goal of defining additional conductors along the Kutcho trend. Due to extensive cover of conductive argillaceous units in the hanging wall, the UTEM system was unable to detect the Esso deposit or other conductors at depth, consequently Teck-Cominco dropped the option.
Homestake was purchased by Barrick Gold Corp in 2003. Western Keltic Mines Inc. purchased the property from Barrick and Sumitomo in early 2004.
In 2004, work by Western Keltic comprised 21 large diameter (HQ) holes totalling 2166 metres at the Kutcho deposit that improved definition of higher-grade areas, slightly extended limits of the deposit and extracted a sample for metallurgical study. Eight holes (625 metres of NQ) also tested the Footwall zone adjacent to the Kutcho deposit. The best overall intercept was near the margin of the Kutcho lens and yielded 8.3 metres grading 5.34 per cent copper, 5.94 per cent zinc, 138 grams per tonne silver, 2.28 grams per tonne gold (Exploration and Mining in British Columbia 2004, page 26). Work in the Esso West lens comprised 12 drillholes that expanded the deposit. Hole 04-27b1, 50 metres beyond the previous western limit of the lens, intersected 5.2 metres grading 3.03 per cent copper, 18.6 per cent zinc, 65.4 grams per tonne silver, 0.93 gram per tonne gold (Exploration and Mining in British Columbia 2004, page 26).
A National Instrument 43-101 compliant resource estimate at Kutcho Creek has outlined measured and indicated resources at the Kutcho deposit (using a 0.5 per cent copper cut-off) of 13.06 million tonnes grading 1.94 per cent copper, 2.59 per cent zinc, 33.7 grams per tonne silver and 0.41 gram per tonne gold (Western Keltic Mines, Press Release, January 11, 2005). The indicated resource estimate for the Esso West deposit is 2.12 million tonnes grading 3.26 per cent copper, 5.86 per cent zinc, 75.7 grams per tonne silver and 0.71 gram per tonne gold (using a 1.5 per cent copper cut-off) (Western Keltic Mines, Press Release, January 11, 2005).
In 2006, Western Keltic Mines Inc. completed an infill diamond drilling program on the Kutcho property from mid-September to the end of October. A total of 1,870 metres were drilled in 23 BTW diameter diamond drillholes.
Further property work plus additional statistical analysis of drill data has led to an updated Mineral Resource value for the property. From the Company news release is the following table:
Main deposit Tonnage (t) Cu% Zn% Ag g/t Au g/t
Measured 2,937,583 1.83 2.65 27.98 0.39
Indicated 12,712,675 1.60 2.04 25.70 0.31
plus indicated 15,650,258 1.65 2.15 26.13 0.32
Inferred 811,103 0.95 1.92 24.17 0.33
Inferred 10,605,030 0.94 1.45 13.96 0.14
Indicated 2,040,445 2.24 3.96 37.70 0.49
Inferred 442,506 2.47 4.15 38.09 0.53
plus indicated 17,690,703 1.71 2.36 27.46 0.34
Inferred 11,858,639 1.00 1.58 15.56 0.17
The qualified person as defined in NI 43-101 responsible for the mineral resource estimate is Tim Carew, P.Geo. The complete NI 43-101 technical report is filed on SEDAR (2007 - June).
In 2007, Western Keltic Mines focused on several aspects of pre-mine development, most of which had a field component. Logistical work involved expansion to a 45-man camp. Baseline environmental studies encompassed acid rock drainage, air quality, archaeology, fisheries, groundwater hydrology and hydrogeology, meteorological data collection, terrain mapping, traditional use characterization, plus vegetation and wildlife inventories. Technical surveys and engineering studies were completed.
In 2008, Sherwood Copper Corporation purchased Western Keltic Mines Inc. and all assets and amalgamated these with Sherwood’s wholly-owned subsidiary which was renamed Kutcho Copper Corporation. In late 2008 Sherwood Copper Corporation merged with Capstone Mining Corporation, forming Capstone Mining Corporation of which Kutcho Copper Corporation was a wholly owned subsidiary.
Between May and August of 2008, Kutcho Copper Corporation completed a major diamond drill program entirely within the perimeter of the Main lens. 9,905 metres of drilling in 78 holes (plus three abandoned holes). This drilling defined higher grade trends within the deposit and provided more confidence in, and thus increased, the classification levels for this new mineral resource estimate.
In 2009, re-logging historic drillcore from the southern area of the claims was carried out in preparation for a surface prospecting and mapping program over the same ground later in the season. A soil sampling survey was followed by a property-wide, helicopter-supported program of mapping and prospecting program.
In 2010 Kutcho Copper Corporation completed a diamond drill program of infill and step-out drilling commenced on Esso deposit which generated significant changes in the Mineral Resource Estimate of Esso deposit. A total of eighteen thousand (17,970) metres of HQ size core was drilled providing more confidence in, and thus increases, the classification levels of the new mineral resource estimate.
In 2010, Capstone released an updated resource estimate for the Esso deposit within the Kutcho project. The estimate is as follows (Stockwatch News Release - December 6, 2010):
Classification Tonnes Cu(%) Zn(%) Au(g/t) Ag(g/t)
Indicated 1,816,200 2.69 6.18 0.66 64.8
In 2011, an airborne electromagnetic survey was conducted over the Kutcho property on behalf of owner/operator Kutcho Copper Corporation using Geotech Ltd.’s proprietary VTEM system for a total of 1649.4 line kilometres covering a 147.2 square kilometre area.
On June 15, 2017, Desert Star Resources Ltd. signed an agreement with Capstone Mining Corp. to acquire 100 per cent of the Kutcho high-grade copper-zinc-gold-silver project. Desert Star also announced the results of an updated prefeasibility study (PFS) prepared in accordance with National Instrument 43-101 for the Kutcho project. Probable mineral reserves at a 1.5 per cent copper cut-off grade of 10.4 million tonnes averaging 2.01 per cent copper, 3.19 per cent zinc, 0.37 gram per tonne gold and 34.61 grams per tonne silver. A 1.5 per cent copper cut-off grade was used for mineral reserve estimation and is based on the 2011 mine plan (Desert Star Resources Ltd., Press Release, June 15, 2017).
On December 20, 2017, Desert Star Resources Ltd. announced a name change to Kutcho Copper Corp. On June 13, 2018, Kutcho announced that more than exploration targets have been identified across the property and have been split into both near-mine drill ready targets and greenfields opportunities.
In 2018, Kutcho carried out a comprehensive review of historic data to identify targets for drilling. Results of this drilling included 28 metres of 2.09 per cent copper, 6.1 per cent zinc, 65.8 grams per tonne silver, 0.82 gram per tonne gold, and 5.4 metres of 2.48 per cent copper, 1.0 per cent zinc, 114.0 grams per tonne silver, and 0.24 gram per tonne gold (Exploration and Mining in British Columbia 2018, page 131).
On November 20th, 2018, Kutcho Copper Corp. released drill results from the Main deposit. The program was designed to reduce the drillhole spacing in the Main inferred mineral resource and test the downdip mineral potential across the deposit. This program was very successful and points to further mineral resource expansion potential with 450 metres of strike along the downdip edge of Main deposit remaining open.
On March 4, 2019, Kutcho Copper reported the expansion of combined (Main, Esso and Sumac) mineral resources to 17.26 million tonnes of Measured and Indicated grading 1.85 per cent copper, 2.72 per cent zinc, 0.49 gram per tonne gold and 33.9 grams per tonne silver; also reported was an Inferred resource of 10.706 million tonnes grading 1.18 per cent copper, 1.76 per cent zinc, 0.26 gram per tonne gold and 21.5 grams per tonne silver (Kutcho Copper Corp., News Release, March 4, 2019). Mineral resource estimates are generated using a total of 362 drillholes at the Main deposit, 118 drillholes at the Esso deposit, and 29 drillholes in the vicinity of the Sumac deposit.