Abstract T he M ining and mineral processing industry is important to the Canadian economy and in 2001 contributed $35.1 billion, or 3.7 percent, to the Gross Domestic Product and employed approximately 376,000 Canadians (Minerals and Metals Sector, Natural Resources Canada). However, over the past decade, Canada’s base metal reserves have declined by more than 25 percent, and significant new discoveries will be required if Canada’s role as a major base metal producer is to be maintained into the twenty-first century. The Bathurst Mining Camp is one of Canada’s most important base metal mining districts, accounting in 2001 for 30 percent of Canada’s production of Zn, 53 percent of Pb, and 17 percent of Ag. In 1999, the Bathurst Mining Camp accounted for 32 percent of the Zn, 80 percent of the Pb, and 25 percent of the Ag reserves (Minerals and Metals Sector, Natural Resources Canada). The value of production from the Bathurst Mining Camp in 2001 exceeded $500 million and accounted for 70 percent of total mineral production in New Brunswick. Approximately 2,000 people are directly employed by the mining industry in the Bathurst Mining Camp. Without the discovery of new ore reserves, however, production will decline and will cease within about 10 yr at current production rates, and with it the principal source of economic activity in northeastern New Brunswick will also disappear. To address the major decline of mineral resources in Canada’s economically important mining districts, EXTECH (Exploration and Technology) projects were established by the Geological Survey of Canada.

Abstract The Bathurst Mining Camp has a long history of discovery and mineral development with the first volcanogenic massive sulfides (VMS) being discovered and drilled at Orvan Brook in 1938. However, the camp did not gain national and international prominence until the discovery of the Brunswick Mining and Smelting 6 deposit was announced in 1953. After that, the Bathurst Mining Camp saw a number of important VMS “firsts” in North America; namely, the first deposits to be described in terms of a syngenetic sea-floor model, the first discovery by airborne electromagnetic surveying, the first discovery by stream-silt geochemistry, the first routine application of gravity surveys to screen ground electromagnetic anomalies, the first (in Canada) heap- and vat-leach operations to recover gold from gossans, and the first major mining camp to be described in terms of ensialic, back-arc–basin-depositional and subduction-related accretionay models. To date, a total of 141 massive sulfide occurrences, including 45 deposits, have been discovered in the Bathurst Mining Camp, a subcircular area approximately 60 km in diameter. About half of the discoveries were made in the 1950s and resulted from the use of geophysics, although geochemistry and prospecting were responsible for many. Later discoveries in the camp can be attributed to improved technology and a better understanding of the stratigraphy and structure. Production to the end of 1998 was over 130 million metric tons (Mt) from 12 deposits. The total massive sulfide resources, including production, from the known deposits in the Bathurst Mining Camp are estimated to be over 500 Mt. The geologic picture of the Bathurst Mining Camp has evolved dramatically since the first massive sulfide discovery. During the early 1950s, the epigenetic period, the geology of the camp was virtually unknown but by the end of the decade five informal units were recognized in the Ordovician Tetagouche Group. The sulfide deposits were considered to be replacement bodies genetically related to Devonian granites. By the 1960s, the syngenetic period, the picture was much the same although the Tetagouche Group was being interpreted in terms of geosynclinal theory and the sulfides were considered to be a facies of iron-formation. By the 1970s, the Kuroko period, plate tectonic theory had been applied to the Bathurst Mining Camp and it was being interpreted as an ensialic arc-related to easterly subduction. The stratigraphic framework of the Tetagouche Group, though informal, and significance of the polydeformational structures were more fully appreciated, and the sulfide deposits were considered to be genetically linked to convective circulation of seawater in proximity to calc-alkaline rhyolite domes. During the 1980s, the VMS period, the geologic picture of the Bathurst Mining Camp started to change because of new mapping and lithogeochemical studies. The Tetagouche Group was interpreted to have formed in an ensialic back-arc rift, with much of its structural complexity related to its amalgamation in an accretionary wedge above a westerly dipping subduction zone. The sulfides were considered to be exhalative, deposited in mounds or brine pools, and to have formed from convective circulation of seawater around subvolcanic intrusions. The deposits were divided into two groups with proximal and distal types in each. In the 1990s, the EXTECH period, the Tetagouche Group was redefined and formally subdivided, largely based on lithogeochemistry and geochronology. Many rocks previously included in this group were reassigned to new groups including the California Lake, Fournier, Miramichi, and Sheephouse Brook Groups. The new data and interpretations resulting from the EXTECH project are described in the papers that follow in this volume.