Minerals Report - International Seabed Authority
Minerals Report - International Seabed Authority Minerals Report - International Seabed Authority
Table 3: Size and Tonnage - Atlantis II Deep (Red Sea) 94 mt - Middle Valley (Juan de Fuca Ridge) 8-9 mt - 13°N Seamount (East Pacific Rise) 5-10 mt - TAG (Mid Atlantic Ridge) 4 mt The largest known marine sulphide deposit is still the Atlantis II Deep in the Red Sea, which was discovered more than ten years before the first black smoker at the East Pacific Rise63 . The Atlantis II Deep mineralisation largely consists of metalliferous muds, instead of massive sulphides, which is a consequence of the high salinity that the hydrothermal fluids acquire by circulation through thick Miocene evaporites at the flanks of the Red Sea rift. A detailed evaluation of the 40 km2 deposit has indicated 94 million tonnes of dry ore with 2.0 wt.% Zn, 0.5 wt.% Cu, 39 ppm Ag, and 0.5 ppm Au64, 65,66 (Table 4) which results in a total precious metal content of roughly 4,000 tonnes of Ag and 50 tonnes of Au. A pilot mining test at 2,000 m depth has shown that this deposit can be successfully mined. Table 4: Atlantis II Deep (Red Sea) Surface area 40 km² Tonnage 94 mt Base metal grades 2.0 wt.% Zn 0.5 wt.% Cu Precious metal grades 39 ppm Ag 0.5 ppm Au Estimates of sizes between 1-100 million tonnes for individual massive sulphide deposits on the seafloor thus are well within the range of typical volcanic-associated massive sulphide deposits on land. However, most occurrences of seafloor sulphides amount to less than a few thousand tonnes, INTERNATIONAL SEABED AUTHORITY 122
and consist largely of scattered hydrothermal vents and mounds usually topped by a number of chimneys with one or more large accumulations of massive sulphide. More than 60 individual occurrences have been mapped along an 8 km segment of Southern Explorer Ridge, but most of the observed mineralisation occurs in two large deposits with dimensions of 250 m x 200 m 67 . The thickness of the deposits is difficult to determine unless local faulting has exposed their interiors. Typical black smokers are estimated to produce about 250 tonnes of massive sulphide per year. Thus, a local vent field with a few black smokers can easily account for a small size sulphide deposit, pending on the duration of activity. Reports of explored dimensions of deposits based on visual estimates from submersibles may be accurate to only +/-50% of the distances given and commonly include weakly mineralised areas between larger, discrete sulphide mounds (thereby over-estimating the continuity of sulphide outcrop). Reports based on transponder navigated camera tracks are probably accurate to +/-20%, but the extent of coverage is limited due to the slow tow-speeds and the narrow image. No geophysical tools currently provide a good basis for estimating the area of sulphide outcrop. High-resolution, deep-towed side-scan sonar may be refined to provide more accurate information over larger areas. 7. Occurrence And Distribution Of Gold Gold grades are locally high in samples from a number of seafloor deposits at the mid-ocean ridges 50, 68,69,70 , and in particular in samples from the back-arc spreading centers 54 . Average gold contents for deposits at the midocean ridges range from
- Page 80 and 81: Volcanogenic Metalliferous sediment
- Page 82 and 83: deposits, including massive sulphid
- Page 84 and 85: 3. Marine Minerals Related to Deep
- Page 86 and 87: The black smoker chimneys dischargi
- Page 88 and 89: contain metals are present at discr
- Page 90 and 91: Figure 4. A diagrammatic east-west
- Page 92 and 93: and refining of these crusts is mor
- Page 94 and 95: distances of hundreds of kilometres
- Page 96 and 97: 2) Deep ocean hot springs at massiv
- Page 98 and 99: 6. P.A. Rona, M.D. Hannington, C.V.
- Page 100 and 101: 25. M.J. Cruickshank (1998), Law of
- Page 102 and 103: With regard to marine mineral depos
- Page 104 and 105: Focussing on sites of sea floor min
- Page 106 and 107: scientific journal "Nature". The su
- Page 108 and 109: Professor Rona recalled that the in
- Page 110 and 111: like St. Stephen’s in the Kremlin
- Page 112 and 113: He noted that another product of ho
- Page 114 and 115: The reasons why the Red Sea deposit
- Page 116 and 117: a number of geothermal wells have b
- Page 118 and 119: 1. Introduction The discovery of hi
- Page 120 and 121: 0° 30° 30° 60° Explorer Ridge C
- Page 122 and 123: 3. Hydrothermal Convection At ocean
- Page 124 and 125: Due to its increased buoyancy at hi
- Page 126 and 127: 5. Metal Contents Despite moderate
- Page 128 and 129: (11.8 wt.%), and have high concentr
- Page 132 and 133: Local enrichment of more than 40 pp
- Page 134 and 135: the Red Sea, Middle Valley, Explore
- Page 136 and 137: Table 8: Advantages of Seafloor Mas
- Page 138 and 139: 60 kg Au) located on the neighbouri
- Page 140 and 141: 9. Perspective If further explorati
- Page 142 and 143: 3. J.M. Franklin, J.W. Lydon, and D
- Page 144 and 145: 19. R.A. Zierenberg, Y. Fouquet, D.
- Page 146 and 147: 35. J. Collier, M. Sinha (1990), Se
- Page 148 and 149: 53. P.M. Herzig, Y. Fouquet, M.D. H
- Page 150 and 151: 68. M.D. Hannington, J.M. Peter, an
- Page 152 and 153: 85. The New York Times (1997), Firs
- Page 154 and 155: southern segment is a fast-spreadin
- Page 156 and 157: Professor Herzig said that the spec
- Page 158 and 159: Professor Herzig said that the depo
- Page 160 and 161: Professor Herzig informed participa
- Page 162 and 163: he informed participants that in ad
- Page 164 and 165: In relation to Conical Seamount, Pr
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- Page 168 and 169: would be removed from the deposit.
- Page 170 and 171: CHAPTER 3 REGIONAL AND LOCAL VARIAB
- Page 172 and 173: � Metallogenic provinces that are
- Page 174 and 175: A digital map of ore-bearing region
- Page 176 and 177: of the slopes in between 1500-3000m
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and consist largely of scattered hydrothermal vents and mounds usually<br />
topped by a number of chimneys with one or more large accumulations of<br />
massive sulphide. More than 60 individual occurrences have been mapped<br />
along an 8 km segment of Southern Explorer Ridge, but most of the observed<br />
mineralisation occurs in two large deposits with dimensions of 250 m x 200<br />
m 67 . The thickness of the deposits is difficult to determine unless local faulting<br />
has exposed their interiors. Typical black smokers are estimated to produce<br />
about 250 tonnes of massive sulphide per year. Thus, a local vent field with a<br />
few black smokers can easily account for a small size sulphide deposit,<br />
pending on the duration of activity. <strong>Report</strong>s of explored dimensions of<br />
deposits based on visual estimates from submersibles may be accurate to only<br />
+/-50% of the distances given and commonly include weakly mineralised<br />
areas between larger, discrete sulphide mounds (thereby over-estimating the<br />
continuity of sulphide outcrop). <strong>Report</strong>s based on transponder navigated<br />
camera tracks are probably accurate to +/-20%, but the extent of coverage is<br />
limited due to the slow tow-speeds and the narrow image. No geophysical<br />
tools currently provide a good basis for estimating the area of sulphide<br />
outcrop. High-resolution, deep-towed side-scan sonar may be refined to<br />
provide more accurate information over larger areas.<br />
7. Occurrence And Distribution Of Gold<br />
Gold grades are locally high in samples from a number of seafloor<br />
deposits at the mid-ocean ridges 50, 68,69,70 , and in particular in samples from the<br />
back-arc spreading centers 54 . Average gold contents for deposits at the midocean<br />
ridges range from
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