CONTENTS 



Page 



World Outlook for Seabed Minerals 39 



General Geologic Framework 41 



Atlantic Region 43 



Sand and Gravel 45 



Placer Deposits 48 



Phosphorite Deposits 52 



Manganese Nodules and Pavements 53 



Puerto Rico and the U.S. Virgin Islands ... 54 



Sand and Gravel 54 



Placer Deposits 55 



Gulf of Mexico Region 55 



Sand and Gravel 55 



Placer Deposits 56 



Phosphorite Deposits 56 



Pacific Region 56 



Sand and Gravel 57 



Precious Metals 58 



Black Sand — Chromite Deposits 58 



Other Heavy Minerals 60 



Phosphorite Deposits 61 



Polymetallic Sulfide Deposits 61 



Alaska Region 65 



Sand and Gravel 67 



Precious Metals 67 



Other Heavy Minerals 69 



Hawaii Region and U.S. Trust 



Territories 69 



Cobalt-Ferromanganese Crusts 70 



Manganese Nodules 75 



Box 



Box P3.ge 



2-A. Mineral Resources and Reserves 40 



Figures 



Figure No. Page 



2-1. Idealized Physiography of a 



Continental Margin and Some 



Common Margin Types 42 



2-2. Sedimentary Basins in the EEZ 44 



2-3. Sand and Gravel Deposits Along the 



Atlantic, Gulf, and Pacific Coasts .... 46 

 2-4. Plan and Section Views of Shoals Off 



Ocean City, Maryland 47 



2-5. Atlantic EEZ Heavy Minerals 51 



2-6. Potential Hard Mineral Resources 



of the Atlantic, Gulf, and Pacific 



EEZs 54 



2-7. Formation of Marine Polymetallic 



Sulfide Deposits 62 



Figure No. Page 



2-8. Locations of Mineral Deposits 



Relative to Physiographic Features ... 66 

 2-9. Potential Hard Mineral Resources of 



the Alaskan EEZ 68 



2-10. Potential Hard Mineral Resources of 



the Hawaiian EEZ 70 



2-11. Cobalt-Rich Ferromanganese Crusts 



on the Flanks of Seamounts and 



Volcanic Islands 71 



2-12. EEZs of U.S. Insular and Trust 



Territories in the Pacific 73 



2-13. Potential Hard Mineral Resources of 



U.S. Insular Territories South of 



Hawaii 75 



2-14. Potential Hard Mineral Resources of 



U.S. Insular Territories West of 



Hawaii 76 



Tables 



Table No. Page 



2-1. Association of Potential Mineral 

 Resources With Types of Plate 

 Boundaries 43 



2-2. Areas Surveyed and Estimated 



Offshore Sand Resources of the United 

 States 48 



2-3. Criteria Used in the Assessment of 



Placer Minerals 50 



2-4. Estimates of Sand and Gravel 



Resources Within the U.S. Exclusive 

 Economic Zone 56 



2-5. Estimates of Typical Grades of 



Contained Metals for Seafloor Massive 

 Sulfide Deposits, Compared With 

 Typical Ore From Ophiolite Massive 

 Sulfide Deposits and Deep-Sea 

 Manganese Nodules 63 



2-6. Average Chemical Composition for 

 Various Elements of Crusts From 

 < 8,200 Feet Water Depth From the 

 EEZ of the United States and Other 

 Pacific Nations 72 



2-7. Resource Potential of Cobalt, Nickel, 

 Manganese, and Platinum in Crusts of 

 U.S. Trust and Affiliated Territories . . 74 



2-8. Estimated Resource Potential of Crusts 

 Within the EEZ of Hawaii and U.S. 

 Trust and Affiliated Territories 75 



