Rona,P.A.(2008): The changing vision of marine minerals. Ore Geology Reviews, 33, 618-666.

『海洋の鉱物についての変わりゆく将来像』

『Abstract
　Non-fuel marine minerals are reviewed from the perspective of resources and their value as active analogs that can advance understanding of types of ancient ore deposits that formed in marine settings. The theory of plate tectonics is the largest influence in expanding our vision of marine minerals and in developing our understanding of geologic controls of mineralization in space and time. Prior to the advent of plate tectonics, we viewed the ocean basins as passive sinks that served as containers for particulate and dissolved material eroded from land. This view adequately explained marine placer deposits (heavy minerals and gems), aggregates (sand and gravel), and precipitates (phosphorites and manganese nodules). Although numerous sites of placer mineral deposits are known on continental shelves worldwide, current activity pertains to diamond mining off southwestern Africa, tin mining off southeastern Asia, and intermittent gold mining off northwestern North America, which are all surpassed economically by worldwide recovery of marine sand and gravel, in turn dwarfed by offshore oil and gas. With the advent of plate tectonics, plate boundaries in ocean basins are recognized as active sources of mineralization in the form of hydrothermal massive sulfide deposits and proximal lower-temperature deposits hosted in oceanic crust (mafic at ocean ridges and felsic at volcanic island arcs), and of magmatic Ni-Cu sulfide, chromite and PGE deposits inferred to be present in the oceanic upper mantle-lower crust based on their occurrence in ophiolites. Some 300 sites of hydrothermal active and relict mineralization, most of them minor, are known at this early stage of seafloor exploration on ocean ridges, in fore-arc volcanoes, at back-arc spreading axes, and in arc rifts; deposits formed at spreading axes and transported off-axis by spreading are present in oceanic lithosphere but are virtually unknown. The TAG (Trans-Atlantic Geotraverse) hydrothermal field in the axial valley of the Mid-Atlantic Ridge (latitude 26゜N) is considered to exemplify a major Volcanogenic Massive Sulfide (VMS) deposit forming at spreading axis. The most prospective of these occurrences lie within the 200 nautical mile (370 km)-wide Exclusive Economic Zone (EEZ) of the nations of the volcanic island arcs of the western Pacific where metal content of massive sulfides (Ag, Au, Ba, Cu, Pb, Sb, Zn) exceeds that at ocean ridges. Plate tectonics early provided a framework for mineralization on the scale of global plate boundaries and is providing guidance to gradually converge on sites of mineralization through regional scales of plate reorganization, with the potential to elucidate the occurrence of individual deposits (e.g., Eocene Carlin-type gold deposits). Investigation of the spectrum of marine minerals as active analogs of types of ancient mineral deposits is contributing to this convergence. Consideration of questions posed by Brian Skinner (1997) of what we do and do not know about ancient hydrothermal mineral deposits demonstrates the ongoing advances in understanding driven by investigation of marine minerals.

Keywords: Marine minerals; Placers; Nodules; Crusts; Massive sulfides; VMS deposits; Magmatic sulfides; Hydrothermal processes; Plate tectonics; Maine environment;Marine mining』

1. Introduction
2. Marine minerals and plate tectonics
3. Marine minerals from terrestrial sources
　3.1. Placer deposits
　3.2. Phosphorites
　3.3. Distribution of marine placers and phosphorite
　　　North America and Central America
　　　South America
　　　Africa
　　　Europe
　　　Asia
　　　Oceania
　3.4. Marine sand and gravel
　3.5. Marine solutes
4. Marine minerals from sources in ocean basins
　4.1. Metalliferous sediments
　4.2. High-temperature massive sulfides
　　4.2.1. Intermediate- to fast-spreading ocean ridges (full-rate of spreading 6 to 18 cm/year)
　　4.2.2. Slow-spreading ocean ridges (full-rate of spreading ＜4 cm/year)
　　4.2.3. Volcanic island arcs
　　　Fore-arc setting
　　　Back-arc setting
5. Modern and ancient VMS deposits and proximal low-temperature deposits
　5.1. Exploration criteria, setting and genesis
　　5.1.1. Exploration procedure
　　5.1.2. Geologic setting
　　5.1.3. Structure
　　5.1.4. Magnetic signatures of detachment faulting and hydrothermal alteration
　5.2. 3-D form and overall composition of TAG active high-temperature sulfide mound
　5.3. Zone refinement in TAG active high-temperature sulfide mound
　5.4. Clustered mode of massive sulfide mounds in the TAG field
　5.5. Chronology of sulfide mounds in the TAG field
　5.6. Proximal low-temperature deposits in the TAG field
6. Seafloor hydrothermal minerals and microbes
7. Magmatic deposits
8. Marine mineral deposits from combined terrestrial and deep ocean sources
　8.1. Manganese nodules
　8.2. Cobalt-rich ferromanganese crusts
9. Discussion
　9.1. Marine minerals and plate tectonics
10. Perspective and conclusions
　　　What we do know
　　　What we do not know
Acknowledgements
References

表７　海嶺と背弧拡大軸からの海底塊状硫化物のバルク組成（Herzig and Hannington, 1995）
　

海嶺

背弧拡大軸

火山性

海洋間

大陸間
n 890 317 28
Fe（重量％） 23.6 13.3 7.0
Zn 11.7 15.1 18.4
Cu 4.3 5.1 2.0
Pb 0.2 1.2 11.5
As 0.03 0.1 1.5
Sb 0.01 0.01 0.3
Ba 1.7 13.0 7.2
Ag（ppm） 143 195 2766
Au 1.2 2.9 3.8

表８　異なる海洋からのマンガン団塊に含まれる金属の平均濃度（Ghosh and Mukhopadhyay, 2000）
元素 大西洋 太平洋 インド洋 世界の海洋
Mn（重量％） 13.25 20.10 15.25 18.60
Fe 16.97 11.40 14.23 12.40
Ni 0.32 0.76 0.43 0.66
Cu 0.13 0.54 0.25 0.45
Co 0.27 0.27 0.21 0.27
Zn 0.12 0.16 0.15 0.12
Pb 0.14 0.08 0.10 0.09
Ir（ppm） 9.32 6.64 3.48 -
U 7.4 7.68 6.20 -
Pd 5.11 72 8.76 -
Th 55.00 32.06 40.75 -
Au（ppb） 14.82 3.27 3.59 -

表９　太平洋と大西洋とインド洋からのCoに富む鉄マンガンクラストに含まれる金属の平均濃度の範囲（Hein et al., 2000）
元素 範囲
Fe（重量％） 15.1-22.9
Mn 13.5-26.3
Ni（ppm） 3255-5716
Cu 713-1075
Co 3006-7888
Zn 512-864
Ba 1494-4085
Mo 334-569
Sr 1066-1848
Ce 696-1684

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