Summary:
Mineralization of the Project is part of the volcanogenic massive sulphide (VMS), or volcanic-hosted massive sulphide (VHMS) spectrum of deposits. The Kutcho deposits are VMS deposits of the Kuroko type or felsic volcaniclastic depending upon the classification scheme. Mineralization is related to felsic volcanism in island arc or back-arc tectonic settings. Perhaps the most significant feature of VMS deposits from an exploration perspective is their tendency to occur in clusters. The Property contains three known Kuroko-type volcanogenic massive sulphide (VMS) deposits. They are aligned in a westerly plunging linear trend and from east to west they are called the Main, Sumac, and Esso deposits.
Mineralization occurs as three deposits along a 3.5 km trend. Sulphide minerals occur in a series of massive sulphide lenses and include pyrite, sphalerite, chalcopyrite, bornite, minor chalcocite, and trace tennantite, galena, digenite, djurleite, and idaite. Gangue minerals include quartz, dolomite, ankerite, sericite, gypsum, and anhydrite.
The three deposits form a westerly plunging linear trend, termed the Main, Sumac, and Esso deposits from east to west. The Main deposit comes to surface at its eastern end, whereas the Esso deposit occurs at depths about 400 m below surface,
Main Deposit
The Main deposit has an elliptical, lenticular shape with approximate dimensions of 1,600 m long, 500 m wide (down-dip), and approaching 40 m in true thickness in some areas. The long axis of the deposit plunges to the west at about 12°, just slightly less than the regional fold axes. The deposit is conformable with stratigraphy, dipping moderately to the north. There is a gentle warping of the deposit, such that the dip of the deposit changes from east to west and north to south. The shallowest dip (about 40°) occurs at the south-eastern edge and becomes progressively steeper (to about 60°) at the north-western edge. In general, the up-dip edge of the sulphide lens is narrow and pinches out, whereas the down-dip edge is thicker and interlayered with tuffaceous rock. Sulphide mineralogy of the deposit is relatively simple, consisting of pyrite, chalcopyrite, sphalerite, and bornite, with minor sulphide minerals chalcocite, tetrahedrite, digenite (and related minerals), galena, idaite, hessite, and electrum. Gangue minerals include quartz, dolomite, ankerite, sericite, gypsum, and anhydrite. The deposit appears to have formed from three hydrothermal-depositional cycles that began with barren pyrite at the base and grade into a copper-rich middle and zinc-rich top. Depositional cycles are commonly separated by layers of exhalative quartz and/or carbonate and minor volcanic ash. However, continued hydrothermal activity resulted in sulphide-replacement mineralization.
Sumac Deposit
The Sumac is located approximately 550 m west of the Main deposit, is nearly continuous with the Esso deposit and sits within a local depression relative to the Main and Esso deposits. A total of 20 drill holes at approximately 100 m spacing define the Sumac deposit. Better intercepts include 1.45% Cu, 2.56% Zn, and 23.7 g/t Ag over 26.1 m, 1.37% Cu, 1.9% Zn, and 26.2 g/t Ag over 23.4 m, and 1.94% Cu, 2.66% Zn, and 43.2 g/t Ag over 10.1 m. The Sumac deposit is finely banded but massive and competent, containing the highest sulphide content (>90%) of the three deposits. Alteration of the host stratigraphy around it is very similar to that of the Main and Esso deposits. The Sumac deposit is not fully delineated with drilling at present but with current knowledge can be described as having an elongated lens shape that commences close to surface near the Sumac Creek, with a strike length of approximately 800 m x 300 m in the dip plane and is up to 25 m in true thickness but averages approximately 12 m thick.
Esso Deposit
The Esso deposit is the deepest and most westerly massive sulphide lens and lies between 350 m and 650 m below the surface. It was discovered by following the westward trend of mineralization down plunge beyond the Main and Sumac deposit areas. The Esso deposit has an elongated lens shape with a strike length of approximately 900 m x 400 m in the dip plane and is up to 25 m in true thickness but averages approximately 12 m thick. Mineralization at the Esso deposit tends to be higher grade than at the Main or Sumac deposits and shows similar mineral zonation with copper or zinc in layers or zones, as well as zonation in thickness and grade from the central deposit area. Although the copper and zinc grades tend to be higher at Esso, the deposit contains significantly lower overall sulphide concentrations compared to the Main and Sumac deposits. Alteration at Esso is similar to the Main deposit, where sericite alteration of feldspars in the hanging wall is gradational from very weak at distances up to 50 m stratigraphically above to deposit, to very intense in proximity to the sulphide zone.
Other Mineralization
Other zones of mineralization include the footwall zone (FWZ), the hangingwall zone (HWZ) and the Jenn Area. The FWZ occurs approximately 120 m stratigraphically below the Main deposit and slightly up-dip and to the east of the centre of the Main deposit. The FWZ is relatively narrow, at 2–5 m thick, and relatively zinc-rich. The mineralization was only systematically drilled up to the historical Esso-Sumac property boundary, but several drill holes by SML (and more recently WKM) demonstrate that the FWZ does not extend for significant distances to the west and down-dip of its current position. The HWZ is a narrow band of relatively low-grade mineralization that occurs within 1–2 m to up to 15 m stratigraphically above the Main deposit. The HWZ is interpreted over a strike length of 1,300 m x 400 m on the dip plane and is often only 1–3 m in thickness.