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50 tonnes of Au. A pilot mining test at 2,000 m depth has shown that this deposit can be successfully mined. 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, 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 thicknesses of the deposits are difficult to determine unless their interiors have been exposed by local faulting. 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 towspeeds 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 mid-ocean ridges range from
during sustained venting of hydrothermal fluids through the sulphide mounds (i.e., zone refining). Table 3. Gold Grades in Polymetallic Massive Sulfides from the Modern Seafloor Conical Seamount (PNG) magmaticepithermal system Immature Back-Arc Ridges (intermediate to felsic volcanics) Au (ppm) range average (N) 0.01 – 230.0 26.0 40 Lau Basin 0.01-28.7 2.8 103 Okinawa Trough 0.01-14.4 3.1 40 Central Manus Basin 0.01-52.5 30.0 10 Eastern Manus Basin 1.30-54.9 15.0 26 Woodlark Basin 3.80-21.1 13.1 6 Mature Back-Arc Ridges (MOR-type volcanics) Mariana Trough 0.14- 1.7 0.8 11 North Fiji Basin 0.01-15.0 2.9 42 Mid-Ocean Ridges 0.01-6.7 1.2 1,259 (MORB) The gold contents of sulphides from deposits in sedimented rifts (e.g., Guaymas Basin) are typically
Page 2 and 3: Polymetallic Massive Sulphides and
Page 4 and 5: The designations employed and the p
Page 6 and 7: Polymetallic Massive Sulphide Depos
Page 8 and 9: Figure 1. Location of hydrothermal
Page 10 and 11: The first sulphide deposits reporte
Page 12 and 13: SEAWATER MASSIVE BLACK SMOKERS MAGM
Page 14 and 15: sulphide mounds commonly consist of
Page 16 and 17: asaltic crust at greenschist facies
Page 20 and 21: samples represent the first known e
Page 22 and 23: Under those circumstances, massive
Page 24 and 25: 3°S New Hanover EL 1205 2557 sq km
Page 26 and 27: 9. PERSPECTIVE If further explorati
Page 28 and 29: 15. W.L. Plüger, P.M. Herzig, K.-P
Page 30 and 31: 40. J.C. Alt (1995), Sub-seafloor p
Page 32 and 33: 65. H.E. Mustafa, Z. Nawab, R. Horn
Page 34 and 35: Cobalt-Rich Ferromanganese Crusts:
Page 36 and 37: over other metals because they are
Page 38 and 39: Table 1 Contents of manganese, iron
Page 40 and 41: Table 2 Classification of marine fe
Page 42 and 43: the instability and mass wasting of
Page 44 and 45: ecovered from seamounts. Fe-Mn crus
Page 46 and 47: The first systematic investigation
Page 48 and 49: 50 International Seabed Authority
Page 50 and 51: - 1.04-2.17 - 1.44-2.92 - 0.78-2.74
Page 52 and 53: the crust surface. Growth rates wer
Page 54 and 55: Hydrogenetic Fe-Mn crusts generally
Page 56 and 57: 58 International Seabed Authority
Page 58 and 59: Sn 5 10 -- 12 -- -- -- 12 3 5 6 --
Page 60 and 61: Figure 7. Shale (PAAS, Post-Archean
Page 62 and 63: Phosphatisation of the older Fe-Mn
Page 64 and 65: proximity to continental margins an
Page 66 and 67: ates. Elements that form carbonate
Page 68 and 69:
5. RESOURCE, TECHNOLOGY, AND ECONOM
Page 70 and 71:
The Japan Resource Association 130
Page 72 and 73:
Table 8. Value of metals in one met
Page 74 and 75:
co-authors of that paper for their
Page 76 and 77:
20. N.S. Skornyakova (1960), Mangan
Page 78 and 79:
41. A.I. Svininnikov (1994), Physic
Page 80 and 81:
Pacific, Marine Mining, 8, 245-266.
Page 82 and 83:
M.S. Schulz and L.M. Gein (67); E.H
Page 84 and 85:
geochemistry and paleoceanographic
Page 86 and 87:
Appendix 1.: Key to symbols in Tabl
Page 88 and 89:
Technical Requirements for the Expl
Page 90 and 91:
2. EXPLORATION TOOLS AND SYSTEMS Ma
Page 92 and 93:
ROPOS (ROV) CSSF Canada 6,000 m JAS
Page 94 and 95:
6. PROCESSING TECHNOLOGIES The phys
Page 96 and 97:
ferromanganese crust mining is curr
Page 98 and 99:
Impact of the Development of Polyme
Page 100 and 101:
nature of the vent organisms, most
Page 102 and 103:
3.1 EPR Vent Ecosystems A schematic
Page 104 and 105:
Different shrimp species occupy dif
Page 106 and 107:
5. RESPONSE TO PERTURBATIONS Recent
Page 108 and 109:
sites, where much of the ore body l
Page 110 and 111:
distribution will require more care
Page 112 and 113:
8. B. J. Burd and R.E. Thomson (199
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