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SEAWATER MASSIVE BLACK SMOKERS MAGMA CHAMBER SULFIDES STOCKWORK 14 International Seabed Authority SEAFLOOR PILLOW LAVAS SHEETED GABBRO DIKES PERIDOTITE Figure 3. Model showing a seawater hydrothermal convection system above a subaxial magma chamber at an oceanic spreading centre. Radius of a typical convection cell is about 3-5 km. Depth of the magma chamber usually varies from 1.5-3.5 km. This highly corrosive fluid is now capable of leaching elements such as Li, K, Rb, Ca, Ba, the transition metals Fe, Mn, Cu, Zn, together with Au, Ag and some Si from the oceanic basement 43. Sulphide droplets in the basalt are considered to be the major source for metals and S 44. The metals are mainly transported as chloride complexes at high temperatures and, in some cases, as bisulphide complexes (in particular Au) at lower temperatures. Due to its increased buoyancy at high temperatures, the hydrothermal fluid rises rapidly from the deep-seated reaction zone to the surface along major faults and fractures within the rift valley or close to the flanks of the rift. In particular the intersections of
faults running parallel and perpendicular to the ridge axis are the loci of high-velocity discharge black smokers and massive sulphide mounds. The sulphide precipitation within the upflow zone (stockwork) and at the seafloor (massive sulphides) is a consequence of changing physical and chemical conditions during mixing of hightemperature (250-400°C), metal-rich hydrothermal fluids with cold (about 2°C), oxygenbearing seawater (Fig. 4). HYDROTHERMAL PLUME METALLIFEROUS SEDIMENT SEAWATER OCEANIC CRUST SO HS 4 2 METAL LEACHING S HS ROCK 2 350-400° C STOCKWORK 400°C HIGH-TEMPERATURE REACTION ZONE MAGMA BLACK SMOKER CHIMNEYS HIGH-TEMPERATURE END MEMBER FLUID 100 M WHITE SMOKER SEAWATER OCEANIC CRUST SULFIDE TALUS HIGH PERMEABILITY LOW PERMEABILITY Figure 4. Cross-section showing the principal components of a seafloor hydrothermal system. 4. MINERALOGY The mineralogy of seafloor sulphide deposits (Table 1) has been documented in a number of detailed studies of samples from various sites 22,45,46,47,48,49,50,51,52. The mineral paragenesis of sulphide deposits at volcanic-dominated mid-ocean ridges usually includes assemblages that formed at temperatures ranging from about 300-400°C to less than 150°C. High-temperature fluid channels of black smokers and the interiors of International Seabed Authority 15
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 14 and 15: sulphide mounds commonly consist of
Page 16 and 17: asaltic crust at greenschist facies
Page 18 and 19: 50 tonnes of Au. A pilot mining tes
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
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The Japan Resource Association 130
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Table 8. Value of metals in one met
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co-authors of that paper for their
Page 76 and 77:
20. N.S. Skornyakova (1960), Mangan
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41. A.I. Svininnikov (1994), Physic
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Pacific, Marine Mining, 8, 245-266.
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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
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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
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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
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5. RESPONSE TO PERTURBATIONS Recent
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sites, where much of the ore body l
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distribution will require more care
Page 112 and 113:
8. B. J. Burd and R.E. Thomson (199
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