Abstract The Matachewan-Kirkland Lake-Larder Lake gold-copper-ironasbestos-barite mining district is situated in Late Archean rocks of the Canadian Precambrian Shield’s Superior Province, -Abitibi sub-province, southwestern part. The structural setting seems to be comparable to Nevada’s Carlin-Battle Mountain “Basin and Range” zone. Prior to modification and in some places up-grading by both tectonically-induced migration and (or) the metasomatic and heatpump effects of later mafic flows and felsic intrusions, a sedimentary phase was essential. Referring to Archean gold deposits in Australia, Tomich (1990) noted that the successful search for new gold ores requires a stratigraphic approach with a structural approach as a secondary adjunct (i.e. the reverse of present practice). A sedimentary phase initiated the accumulation of what has become the Matachewan-Kirkland Lake-Larder Lake and other similar gold ores. The purpose of the following text is to describe this sedimentary protore-generating phase. The total amount of gold produced from the 100 km-long Matachewan-Kirkland Lake-Larder Lake mining district, from approximately the beginning in 1910 until 1990, was more than 37 million Troy ounces. Most production was selectively mined so that the historical average grade (and in some cases the cut-off grade!) is almost 1/3 of a Troy ounce per short ton (about 10 grams per metric tonne). Among large Canadian gold mining districts this grade is exceeded only by the Northwest Territories (predominantly Yellowknife) and Ontario's Red Lake, and this production only by the Porcupine (Timmins).

Abstract Introduction The base metal and barite deposits of the Silvermines district occur on the northern flank of the Silvermines Mountains, some 8km south of the market town of Nenagh in northern County Tipperary. The earliest records of mining in the area date back to the early 9th century when argentiferous galena was mined by the Danes. From the 16th to the 19th century subsequent operations along the Silvermines Fault raised copper, silver, lead, zinc and sulfur ores. In this century, mining of calamine (smithsonite) at Ballygowan South and lead at Shallee continued sporadically until 1958. The major base metal and barite deposits were discovered in 1962 by geologically directed diamond drilling, and worked until July 1982 by Mogul of Ireland Ltd., and until September 1993 by Magcobar Ltd. (Dresser Industries) respectively. The Mogul mine produced some 10.8Mt of ore grading 2.70% Pb and 7.36% Zn from 1968 until closure, from underground workings on the Upper G, Lower G, B and K Zones (Table 1; also see page 246). The Magcobar operation produced approximately 4.6Mt of 85% BaS0 4 lump barite. Currently (1994) the Silvermines area is being explored by Ennex International Pic in joint venture with Rayrock Yellowknife Resources Limited who hope to add to the known remaining base-metal ore reserves of 6,894 929t grading 2.26% Pb and 4.98% Zn.