Deposits of marine phosphorite'* nodules are 

 found on continental shelves and the upper parts 

 of slopes, as well as on submarine banks and 

 ridges. Although the nodules in places have been 

 washed by bottom currents and perhaps concen- 

 trated to some extent as silt and clay were 

 winnowed away, they are not of detrital origin like 

 the placers but are derived from erosion of 

 Tertiary phosphatic beds exposed on the sea floor 

 or precipitated from sea water, forming in areas of 

 cold upwelling, nutrient-rich waters.*' 



Not all of the west coast placer minerals are 

 likely to be found in individual deposits. In the 

 history of west coast placer mining only gold, 

 platinum, and minor amounts of tin have been 

 recovered in commercial operations. Off the coast 

 of Alaska there may exist minable resources 

 amounting to millions of ounces of gold, hundreds 

 of thousands of ounces of platinum, and thou- 

 sands of tons of tin. Minable deposits of gold and 



3. Deposits in the Substrate of Shelves and Slopes 



, The principle resources locked in the sub- 

 strate rocks of the continental shelves and 

 slopes are oil, gas, and sulphur. However, other 

 potentially important resources in this environ- 

 ment include coal, bedded salt that may contain 

 potash-rich layers, phosphatic rock, iron ore, 

 bauxite, beds rich in placer minerals, and possibly 



Table 6 



OFFSHORE MINING OPERATIONS IN 1967 



CONSOLIDATED DEPOSITS 



Source: Charles M. Romanowitz, Michael J. Cruickshank, and Milton P. Overall, "Offshore Mining Present and Future,' 

 presented at NSIA/OSTAC Ocean Resources Subcommittee meeting, San Francisco area, April 26, 1967. 



Estimated. 



platinum may be present off the coasts of Oregon 

 and California. Ilmenite is the sole product from 

 some east coast placers, but others contain as 

 potential products all those Usted above. 



See Appendix A for fuller discussion of phosphorite. 



' 'v. E. McKelvey and Livingston Chase, "Selecting 

 Areas Favorable for Subsea Prospecting," in Exploiting 

 the Ocean, (Washington, D.C.: Marine Technology Socie- 

 ty, 1966) p. 46. 



VII-104 



