Exploration and mining in the Southwest Region, British Columbia Bruce Northcote1, a 1 Regional Geologist, British Columbia Geological Survey, Ministry of Energy, Mines and Low Carbon Innovation, 300-865 Hornby Street, Vancouver, BC, V6Z 2G3 a corresponding author: [email protected] Recommended citation: Northcote, B., 2021. Exploration and mining in the Southwest Region, British Columbia. In: Provincial Overview of Exploration and Mining in British Columbia, 2020. British Columbia Ministry of Energy, Mines and Low Carbon Innovation, British Columbia Geological Survey, Information Circular 2021-01, pp. 121-134. 1. Introduction allowing more time to fi le assessment work, cash in lieu, or The Southwest Region (Fig. 1) has a long history of mining. lease payments, making a decrease unlikely in 2020. This history includes: the use of native copper by First Nations; silver, gold, and coal mining by the mid-19th century; mining of 2. Geological overview iron in the mid-20th century; and substantial copper production Metallogeny in British Columbia is closely linked to the throughout the 20th century. Although mining and exploration tectonic evolution of the Canadian Cordillera, fi rst as an for metal and continues in the region, most mining is for accretionary orogen consisting of allochthonous terranes that construction materials, mainly aggregates for local markets were welded to and deformed with the western margin of with some exports from the largest coastal quarries. ancestral North America, primarily during the Jurassic, and The area has one major polymetallic metal mine, Myra then as the site of post-accretionary tectonism and magmatism Falls (Nyrstar N.V.), one coal mine on care and maintenance, (e.g., Nelson et al., 2013). Quinsam (ERP Compliant Fuels LLC), and numerous industrial The Southwest Region includes parts of the Insular, Coast, minerals and aggregate operations. Having been on care and and Intermontane physiographic regions. Most of the area maintenance since 2015, Nyrstar prepared to return Myra Falls is underlain by rocks of the Wrangell terrane and the Coast to production in 2017 and produced some concentrate in 2018. Plutonic complex (Fig. 1). Wrangellia is a Devonian to Jurassic Operations were suspended in 2018 for compliance reasons but island arc terrane that underlies most of Vancouver Island restarted in April 2019 and continued in 2020. The Quinsam and Haida Gwaii. The oldest rocks on Vancouver Island are mine, on care and maintenance since 2016, had returned to Devonian volcanic arc andesites, basalts, breccias, tuffs, production in 2017, after being purchased by ERP Compliant and tuffaceous sediments of the Sicker Group and allied Fuels LLC, and produced about 200,000 t in 2018. However, intrusive rocks, which are overlain by Mississippian-Permian the mine was placed on care and maintenance again in May limestones, argillites, and minor conglomerate of the Buttle 2019 and remained so through 2020. Lake Group. This Paleozoic basement is exposed in two Mine site exploration at Myra Falls, which began late in major uplifts on southern and central Vancouver Island. The 2017, continued in 2018 through 2020. Privateer Gold Ltd. Cowichan anticlinorium and the Buttle Lake anticlinorium host continued a signifi cant exploration program at Zeballos, and the past volcanogenic massive sulphide polymetallic producer more than 30 other exploration projects were tracked, mainly at Mount Sicker and the current mine at Myra Falls. grass roots or early stage and small scale. Unconformably overlying the Paleozoic rocks are Middle to Estimates for exploration expenditures, drilling programs, Upper Triassic oceanic fl ood basalts and related sedimentary and other metrics were captured in the British Columbia Mineral rocks of the Vancouver Group. The upper part of the Vancouver and Coal Exploration Survey, a joint initiative of the Province Group contains numerous skarn occurrences adjacent to Jurassic of British Columbia Ministry of Energy, Mines and Low intrusions (Island Plutonic suite). The Tasu past producer on Carbon Innovation, the Association for Mineral Exploration Haida Gwaii is one of the larger examples of numerous iron in British Columbia, and EY LLP. For the Southwest Region, and iron-copper skarns. Between 1914 and 1983, it produced exploration expenditures were estimated at $4.0 million and 12 Mt of iron concentrate as well as copper, gold and silver. exploration drilling was estimated at approximately 23,000 m The Vancouver Group is overlain by arc rocks of Bonanza (Clarke et al., 2021; EY LLP, 2021). Group (Upper Triassic-Middle Jurassic), which consist of The total area under mineral, placer, and coal tenure in the a volcano-sedimentary succession and subaerial basalt to region was about 689,700 ha in late November 2020, a 10.5% rhyolitic fl ows and tuffs (Nixon and Orr, 2007). The Bonanza increase relative to November 2019 (624,000 ha). The Chief Group north of Holberg Inlet host the past-producing Island Gold Commissioner issued a blanket extension order in March, Copper Cu-Mo-Au porphyry deposit and other undeveloped 121 Provincial Overview of Exploration and Mining in British Columbia, 2020. British Columbia Geological Survey, Information Circular 2021-01 Northcote Fort St. James Prince Rupert Houston Î Burns Lake Masset Kitimat Fraser Lake Vanderhoof Prince George Hixon M Wells Foreland Quesnel Intermontane Insular Omineca Gold Standard É! Bella Coola Coast Cordilleran PACIFIC OCEAN morphogeological Goldstar Williams Lake É! belts Property status coloured by project type (! Operating Mine* 100 Mile House ÌÌ (! Mine in Care and Maintenance** (! Proposed Mine É! Exploration Project *Operated in, or for a portion of 2020 Southwest **Operated within the last 3 years Bute Inlet Regional Project type ÌWX Districts Cache Creek Coal Port Hardy North Island WX Vulcan/Salal (! Cu-Mo, Cu-Au-Ag, Mo (porphyry) Bakar É! É! Orca Great Pacific Pumice ÌWX (! Precious metal Yreka ÛÚ ! É! Ì ( Base and precious metal É! NVI Leo D'Or Lemare É! É! # (! Cobalt, base and precious metal É! WX Adam West Lytton (! Ni-Cu-Co-precious metal Teeta Creek Empire Mine É! Merri Brandywine (! Tungsten Consortium ! É! Campbell River É (! Specialty metal É! Ì New Privateer Treat Creek WX Jade É! Quinsam Ì Tahsis Dancer ÛÚ WX Spumoni WX Industrial mineral WX É!Ì Ì WX CTCT WXWX WX ÛÚ Earle Creek ÛÚ Aggregate projects Ì Myra Falls Ì Ì ÌSechelt Carbonate Ladner Gold Ì WX É! (! Hardy ÛÚ Burnco Aggregate Geology 0 Kilometres 100 Ì Island ÛÚ Harrison Gold Blubber Bay Ì Pipeline Road É! É! Post accretionary assemblages Sechelt Mine ÛÚ ÛÚ Pitt River Imperial Limestone Port Alberni VancouverÎ ÌÌ Silver Peak Intrusives Supracrustal Neogene to Transportation Texada Quarry ÛÚ Cox Station Quaternary volcanics Sumas ShaleÌWX Terranes Î Port Ì Ferry route É! Outboard Alexander Stikinia Road Angus Cache Creek and Wrangellia Quesnellia Rail line UNITED STATES OF AMERICA affiliates K2 Stone Quarry WX Major faults Ì ÎVictoria Fig. 1. Mines, proposed mines, and selected exploration projects, Southwest Region, 2020. Terranes from Nelson et al. (2013). 122 Provincial Overview of Exploration and Mining in British Columbia, 2020. British Columbia Geological Survey, Information Circular 2021-01 Northcote porphyry and epithermal prospects where they are intruded by Leech River has been an active placer gold camp since 1864. Island Plutonic suite granodiorite and quartz diorite. Gold quartz veins have been the subject of recent exploration On the east coast of Vancouver Island, in the Strait of Georgia near the Leech River fault, along the southern margin of the and on the western mainland, Wrangellia is buried by rocks terrane (Fig. 1). of the Nanaimo Group, an Upper Cretaceous continental to The Crescent terrane represents Eocene accretion of Late marine molassoid succession containing debris derived from Cretaceous or Paleocene to Early Eocene seamounts. The Leech unroofi ng of the Coast Belt and northern Cascades (Mustard, River fault marks the boundary of Pacifi c Rim and Crescent 1994). The Comox Formation, the basal unit of the Nanaimo terranes. The Metchosin Igneous complex, a partial ophiolite Group, hosts economically important coal deposits that were and northernmost extent of the Coast Range basalt province mined historically in the Nanaimo area. (Massey, 1986), contains three tholeiitic intrusion-hosted past The Coast Mountain range is underlain by the Coast Plutonic producers of copper and precious metals, the most signifi cant complex, a large northwest-trending batholith consisting of which was the Sunro mine. largely of diorite, quartz diorite, tonalite, and granodiorite The southeastern Coast Belt, north of the international calcalkaline rocks with less abundant high-grade metamorphic border is underlain by the Nooksack-Harrison and Chilliwack rocks. For the most part, uplift and erosion have removed the terranes (equivalent to Stikinia; Monger and Struik, 2006), and levels at which epithermal and porphyry-style mineralization the Bridge River, Cadwallader, and Methow terranes, allied form, with some exceptions. At the southern end of the Coast with the main Cache Creek terrane (Fig. 1). These represent Plutonic complex, economically important deposits occur in slices of oceanic and arc-related rocks enclosed between pendants of the Gambier Group, overlapping Late Jurassic to Intermontane and Insular terranes during Middle Jurassic to Mid-Cretaceous arc-related volcanic and sedimentary rocks. Middle Cretaceous regional sinistral faulting