oxide, and they occur on the deep ocean floor as 

 well as on the lower parts of the continental 

 slopes. 



5. Deposits in the Substrate of the Deep Ocean 

 Basins 



The rocks beneath deep ocean floors are be- 

 lieved to be principally basic and ultra-basic rocks 

 of igneous origin. Therefore the types of mineral 

 deposits that might be found in this environment 

 are restricted to those commonly associated with 

 the same kinds of rocks on land. Chromite and 

 nickel appear the most likely. Soviet ocean- 

 ographers have recently found pure chromite in 

 sea floor rifts in the Indian Ocean. Deposits of the 

 Red Sea type (described in the following section) 

 are also likely in certain areas. 



6. Metals Deposited from Submarine Hot 



Waters^^ 



Copper, zinc, silver, lead, tin, and gold were 

 found to occur in significant quantities in hot 

 brines and metal-rich sediment in one of the deeps 

 of the Red Sea in 1965.^^ Subsequent studies 

 have revealed similar deposits in two other 

 deeps.^" One of these, the Atlantic II deep, has 

 been estimated by F. T. Manheim^ to contain the 

 following concentrations in the upper 10 meters of 

 sediment: 



Per cent by weight 

 Copper Zinc Silver Lead Tin Gold 



0.90 



2.6 0.008 0.10 0.002 0.0001 



Iron and manganese are also present in large 

 quantities. These metals, along with barium (in 



Summarized from V. E. McKelvey et al, "Potential 

 Mineral Resources of the United States Outer Continental 

 Shelves," unpublished report of the Geological Survey to 

 the Public Land Lavi' Review Commission, March 1968. 



23 



A. K. Miller et al, "Hot Brines and Recent Iron 

 Deposits in Deeps of the Red Sea," Geochimica et 

 Cosmochimica Acta, Vol. 30, 1966, pp. 341-359. 



E. T. Degens and D. A. Ross, "Hot Brines and Heavy 

 Metals in the Red Sea," Oceanus, Vol. 8, June 1967, pp. 

 24-31; J. L. Bischoff and F. T. Manheim, "Economic 

 Potential of the Red Sea Heavy Metal Deposits," Red Sea 

 (in press). 



25 



F. T. Manheim, unpubUshed memorandum. Geologi- 

 cal Survey, April 28, 1967. 



barite) and mercury (in cinnabar) are among the 

 metals that in some deposits are thought to have a 

 hot springs origin.^* It seems likely that a variety 

 of metalliferous deposits may be found on the 

 ocean bottoms in association with submarine hot 

 springs. 



Whether or not such deposits of hot brine and 

 metalliferous muds occur on U.S. continental 

 shelves and slopes is wholly speculative, but 

 superheated metal-rich Salton Sea brine^^ appears 

 to be of the same origin and the Pacific margin is 

 one of the tectonic belts in which comparable 

 hydrothermal (hot solution) activity is taking 

 place now or took place in the recent past. 



The deep ocean floors beyond the continental 

 margins contain vast amounts of manganese 

 nodules and red clays. Other valuable minerals not 

 now suspected may he either on or beneath the 

 floors of the deep oceans. 



Recommendation : 



Bathymetric charting of the deep ocean floors 

 beyond the continental slope together with geo- 

 logic and geophysical study of the deep ocean 

 areas and appraisal of its resource potential should 

 start in a modest way and build up to a funding 

 amounting to about 25 per cent of the Continental 

 Shelf and slope program within five years. The 

 surveys should be at recoimaissance scale and the 

 program of bathymetric, geophysical, and geologi- 

 cal mapping should be closely coordinated. Priori- 

 ties should be given to areas most likely to 

 enhance knowledge of how mineral deposits are 

 formed. Such areas would include the great frac- 

 ture zones of the pacific, the mid-Atlantic Ridge, 

 and the Red Sea rift zone. 



II. Present State of the Marine Mining Industry 



During 1967 there were nearly 300 recorded 

 operations, worldwide, engaged in the production 

 of hard minerals from marine sources, according to 

 the Bureau of Mines. AH of these operations are 

 nearshore and involve extraction of minerals from 

 three of the basic types of deposits: sea water; 



D. F. Hewlett, "Stratified Deposits of the Oxides and 

 Carbonates of Manganese," £'conoffHC Geology, Vol. 61, 

 No. 3, 1966, pp. 431-461. 



^'d. E. White, J. D. Hemley, and G. A. Waring, 

 "Chemical Composition of Subsurface Waters," Geologi- 

 cal Survey Professor Paper No. 440-F, 1963. 



VIM07 



