GEOLOGY AND MINERALIZATION
The Stewart Property is located in a region of much historic mining activity, with the Ymir, Erie, Sheep Creek and Nelson districts being sites of extensive exploration and production for over 100 years. Stewart is part of a large geologic trend of gold, silver, molybdenum, tungsten, copper, and other mineralization. The trend contains:
- Emgold's Rozan Property (gold);
- Emgold's Stewart Property (gold, silver, molybdenum, tungsten);
- Altair Venture Corporation and Sutlan Minerals Incorporated Kena Property (gold);
- Valterra Resource Corporation's Star and Toughnut Properties (gold, silver);
- Sultan Minerals Incorporated's Jersey Emerald Property (tungsten, lead-zinc, molybdenum);
- Duncastle Gold Corporation's Yankee Dundee Property (gold); and
- Valterra Resource Corporation's Swift Katie Property (copper).
The Stewart Property is located west of Altair Ventures/Sultan Mineral's Kena Property and Duncastle Gold's Yankee Dundee Property. Sultan Minerals reports that the Kena Property a gold resource of 541,000 measured and indicated ounces of gold (24.9 million tonnes at 0.68 gram per tonne gold) and an inferred resource of 557,000 ounces of gold (25.8 million tonnes at 00.67 gram per tonne gold) (see NI 43-101 compliant technical report at sedar.com). Duncastle Gold reports that the Yankee Dundee Property hosts a number of historic gold mines, the largest of which was the Yankee Girl, where a reported 375,000 tons of ore was mined on 14 levels between 1907 and 1951). Note that the presence of the resource on the Kena Property and the presence of historic mines in the area do not imply that similar results will be achieved at the Stewart Property. However, geological mapping of the various properties does show similar geologic structures that overlap on the properties.
Geology and mineralization of the Stewart Property is well understood following the various exploration programs that have been undertaken over the years, including Emgold's work. Refer to the Stewart Property Geology Map.
The oldest rocks in the region are clastic sedimentary rocks of the Proterozoic Aldridge (Belt) Supergroup, which outcrop in the eastern part of the region. The main bedrock units consist of Paleozoic clastic and carbonate sedimentary rocks of the Kootenay Terrane, also situated in the eastern part of the region, and Mesozoic volcanic rocks of the Quesnel Terrane to the west. The stratigraphic units of both the Kootenay and Quesnel Terranes have been folded and faulted along an east-west compressional axis. They are intruded by felsic volcanic rocks that range in age from Jurassic to Tertiary. Small coeval dioritic intrusions are common in the mafic andesitic volcanic rocks of the Jurassic Rossland Group. Extensive late Mesozoic intrusive activity produced the widely distributed Nelson Group of intrusives of granitic to dioritic compositions. Monzonite intrusive rocks of the Eocene-age Coryell Group, are also widely distributed in the region. Young (Tertiary) dikes and sills of rhyolite and felsite are common, and some small, more mafic intrusives are present.
The Stewart Property is underlain primarily by sedimentary and volcanic rocks of the Jurassic Rossland Group, along with intrusive rocks of various younger ages. These rocks have been structurally deformed and faulted, and mineralization appears to be structurally controlled.
Rocks of the Rossland Group are the Elise Formation, composed of volcanic lithologies, and the Hall Formation, consisting of clastic sedimentary rocks.
The Jurassic age Elise Formation is mostly of basaltic to andesitic composition, but range from andesite to gabbro. The formation includes flows, breccias, pyroclastics, and sub-volcanic intrusives. Diorite intrusives occur in the andesite pile and make up a significant part of the formation. These rocks range from very weakly to moderately magnetic. The volcanics underlie a large portion of the Craigtown Creek area, and host a significant part of the known mineralization. They strike generally north-south and dip moderately to steeply east.
Overlying the Elise Formation on the east is the Hall Formation. Rocks of the Hall Formation are mostly siliceous argillite, siltstone, fine-grained sandstone, conglomerate, and tuffaceous rocks. These rocks strike north-south and dip steeply. Mineralization of these rocks on the Stewart property seems to be restricted to the contact aureole around the "West Moly Intrusion", to the east. This mineralization is limited to disseminated pyrite/pyrrhotite and minor small quartz-sulphide veins. Alteration in this aureole includes silicification and hornfels.
The Cretaceous Nelson intrusive suite consists mostly of quartz monzonite, monzonite, granite and diorite. The intrusive masses tend to be large, and outcrop most extensively in the northern portion of the property, in the Stewart and Craigtown Creek drainages. Smaller stocks occur in the western portion of the property. The rocks exhibit weak to fairly strong magnetism and propylitically altered near contacts with country rocks. These rocks are important because the porphyry molybdenum mineralization on the property is thought to be related to these intrusives.
Younger intrusives of the Coryell Suite (Eocene or later?) are also monzonitic, but tend to be a little more quartz-poor and alkaline than the Nelson rocks. They occur in both the east central and west central portions of the property.
Younger igneous rocks include intrusive breccias that show several cross-cutting relationships. They are altered and mineralized, and are associated with anomalous Au and Cu geochemistry in both soils and rocks. Several percent magnetite is a common component, both as fine to medium-grained disseminations and as stockwork veinlets, with or without quartz. Potassium feldspar and quartz veining and flooding are present in places.
The youngest intrusives are rhyolite, latite and minor basalt sills/dikes that intrude the older Rossland rocks and both Nelson and Coryell intrusives. They are also probably Tertiary age, as they intrude the Rossland Group and the diorite and monzonite intrusives. They generally strike north-south and dip near vertically. The dikes are a few metres in width and have strikes that range from northwest to northeast with steep dips. They are usually not altered or mineralized, however, a small plug of a trachytic latite and quartz latite porphyry with quartz veinlet stockwork and anomalous Au (>1 g/t) outcrops in the Craigtown Creek area.
Rhyolite, lamprophyre, porphyritic basaltic dikes and small plugs occur on the Stewart Property. Some of them contain disseminated pyrite and some earlier workers concluded that they are the source of the Au soil geochemical anomalies at Craigtown Creek. They also intrude the Rossland Group and the diorite and monzonite intrusives. They are probably late and unrelated to mineralization.
The dominant structural grain on the property is north-south. The Rossland Group stratigraphy generally strikes north-south, and the Elise and Hall Formations were folded into a broad north-south trending syncline (Hall Creek Syncline) that runs through the property and extends both north and south over a 20 kilometer strike length. Northwest and northeast-trending faults and shear zones exist on the property and appear to be significant controls to mineralization. The younger rhyolite dikes and sills also strike north-south and dip steeply.
Various types of alteration have been observed on the Stewart Property. In the area of the porphyry molybdenum occurrences phyllic and potassic alterations were reported by earlier workers. Silicification is common in various rock types. Propylitic alteration of intrusive and volcanic rocks is widespread on the property. In the Craigtown Creek area propylitic, silicification, carbonate, potassic and skarn alterations are present.
Propolylitic alteration, silicification and carbonate alteration are present within the Elise Formation andesite near Craigtown Creek. The silicification is usually accompanied by disseminated pyrite or pyrrhotite and is coincident with gold-copper-arsenic anomalous soil and rock geochemistry in places. Most of the carbonate appears to be a late alteration product.
Potassic alteration is present in places in brecciated and veined fine-grained felsic monzonite intrusive rocks along the Bonnington Pluton/Elise Formation contact. Quartz +/- magnetite veinlets are commonly associated with this alteration.