Atlantis-II-Deep's Metal Reserves and Their Evaluation

Abstract

ABSTRACT The Atlantis-II-Deep's metalliferous sediments were recently discovered along the mid-ocean ridge system extending into the Red Sea, at a mean water depth of 2,200 m. The average thickness is 7 to 11 m in different sub-basins. The metal-bearing mud contains sulfides of zinc, cupper and iron with significant amounts of silver, gold and cobalt. A variety of oxide, siliceous and carbonaceous gangue minerals are also present. To determine the in-situ characteristics pertaining to the variability of the metal grades and mineralized thickness, and to study the natural phenomena, mining geostatistics was applied to estimate the Red Sea offshore mineral resources. Horizontal experimental variograms were computed along 0±180 degrees and then models were fitted to analyse the mineralization in each area. Kriging estimates indicate that 696.330 million tons of bulk sediments contain 1.891 million tons of zinc, 0.425 million tons of copper and 3.75 thousand tons of silver. Gold and cobalt contents were calculated from the analysis of solids in flotation concentrates as 47 tons and 5,368 tons respectively. The significant outcome of implementing geostatistics to the Red Sea brine preciptates is not only for the evaluation of metal reserves, but it also provides a useful tool in the optimization of selective dredging of appropriate areas to be mined. INTRODUCTION The Atlantis-II-Deep is a unique marine deposit with a 2,200 m-thick sea water overburden. The stratified muds consist of varying quantities of very fine grained oxides, silicates and sulfides of zinc, copper and iron, and considerable concentrations of gold and cobalt. Extensive systematic exploration has revealed the fact that brine precipitates formed this potentially mineable orebody of economic interest. The resource potential and economic worth of the Atlantis-II-Deep has been studied at different times utilizing data provided by exploration campaigns. The following are those worthy of mention. In 1969, Bischoff and Manheim (1) assessed the in-situ value of the deposit at $2.5 billion, based on 41 analyses from 7 piston core samples that were collected during the Chain cruise. This represents:2.9 x106 tons of zinc,1.06x106 tons of copper,8.0 x104 tons of lead,4.5 x103 tons of silver, and4.5 x10 tons of gold. In 1969, the Wando River cruise yielded channel samples from 28 stations within the Hackett and Bischoff (2)in 1973 calculated the estimates and amount of valuable metals in ore on the dry-salt-free material as:32.7 x105 tons of Zn at a grade of 3.48 x103 g/m38.2 x105 tons of Cu at a grade of 0.869xl03 g/m384.01x107m3 of sediment volume. This amounted to a total value of $ 2.33 billion for in-situ resources at the 1972 market metal prices.2.4 x106 tons of zinc,0.5 x106 tons of copper, and8.6 x103 tons of silver. The economic value at this time reached $ 4.2 billion. In 1977/1978 and 1979, Meseda 1 cruise of Sonne and Meseda 2 cruise of Valdivia were undertaken to obtain an additional 195 statistically distributed core samples.