Carter--Manganese nodules in the Pacific

New Zealand Journal of Marine and Freshwater Research abstracts

New occurrences of manganese nodules in the South-western Pacific Basin, east of New Zealand

LIONEL CARTER

New Zealand Occanographic Institute Division of Water Sciences Department of Scientific and Industrial Research Private Bag, Kilbirnic, Wellington, New Zealand

Abstract Manganese nodules were recovered from 2 new sites, 1020-1220 km south-east of New Zealand. This discovery extends the northern limit of a nodule belt, formed along the base of the Campbell Plateau, to latitude 49°S and probably to 48°S where the belt is curtailed by sediments of the Bounty Fan. The first site is within New Zealand's Exclusive Economic Zone (EEZ) and occupies a 4760 m deep channel in Bollons Gap separating the plateau from Bollons Scamount. Here, small (1-3 cm diameter), free-standing nodules arc concentrated mainly within depressions between mounds of sandy sediment. Bcdforms indicate this sediment has been eroded, presumably by a deep western boundary current as it intensifies through Bollons Gap. The second site is outside the EEZ, near the 5100 m deep, eastern base of Bollons Scamount. While still within the path of the western boundary current, the flow is slower than at the first site judging by the presence of "red clays". Nodules here are larger (4-8 cm), more spheroidal, and more densely packed, forming a distinctly nodular pavement with few free-standing nodules. The economic potential of these deposits is considered low by present mining criteria because of the low to moderate concentrations of nodules and their low copper (0.11-0.16%), nickel (0.15-0.22%), and cobalt (0.21-0.25%) contents.

Keywords manganese nodules; South-western Pacific Basin; western boundary current; New Zealand Exclusive Economic Zone

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