Abstract The 1991 discovery of the diamondiferous “Point Lake” kimberlite in the Lac de Gras region of the Archean Slave craton ignited one of the greatest staking rushes in history. Rio Tinto initiated a large land consolidation, predominantly up-ice and to the south of the BHP-DiaMet Point Lake discovery, including a 600,000-ha property owned by Aber Resources Ltd. Exploration commenced on this property in 1992 with airborne geophysics and kimberlite indicator mineral sampling. Prior to drilling, targeting decisions utilized ground geophysical surveys that resulted in a high (>90%) kimberlite discovery success rate. Early discoveries were made by drilling strongly magnetic (but reversely polarized) lows. Subsequent discovery of diamondiferous kimberlites characterized by conductive anomalies with subtle to no magnetic responses changed the exploration paradigm. The East Island area in Lac de Gras contained a preponderance of high-interest indicator minerals; drill testing of several conductive anomalies as imaged by EM techniques resulted in the discovery of kimberlites that would eventually comprise the Diavik diamond mine orebodies. Microdiamond results from more than 60 kimberlites on the property indicated that A154N, A154S, A21, and A418 were the most likely pipes to contain economic grades. Subsequent large-diameter drilling confirmed that A154S and A154N were indeed high grade, with respective sample grades of 4.59 and 2.32 carats per tonne. Initial delineation drilling and favorable valuation of 240 carats from A154S prompted the authorization of a $60 million feasibility study by the end of 1995. The rapid discovery of Diavik was a result of the quick decision to acquire significant land in and surrounding Lac de Gras, the utilization of state-of-the-art geophysical techniques, the sound implementation of kimberlite indicator mineral exploration in glaciated terrains, and the use of microdiamond size-frequency curves to rank the kimberlites and assess the macrodiamond potential.

Abstract Offshore mining for minerals such as barite, coal, calcium carbonate, gold, and tin is a well-established industry in many countries. Although there have been several attempts to develop mining systems to recover manganese nodules in water depths of 4,000 m, commercial mining is at present confined to shallow coastal waters. Undersea mining for sub-surface deposits dates from at least the early 1600s and accounts for a significant proportion of the total mineral production in some countries. More than 100 undersea mines have been constructed worldwide; with few exceptions they began as onland mines that moved offshore after the onland sources were depleted (Austin, 1967). In 1977, the last year for which comprehensive global production statistics are available, offshore non-fuel mineral production was worth about $460 million, with most of that coming from sand and gravel, tin, and calcium carbonate (Glasby, 1979). This valuation is conservative because numerous small operations go unreported and the Soviet Union does not make public its production statistics. The Soviet Union has, for several years, dredged cassiterite for tin in the Arctic Ocean, but we have no information regarding the level of production. Most marine mining activity to date has taken place in temperate or tropical regions, yet the Arctic may host equally exciting mineral deposits, and both tin and sand and gravel are already mined there. The problems of mining in a region covered by ice for much of the year should not, however, be underestimated. New technologies will be required for exploration and mining