Table 4 

 AVERAGE AND TOTAL CONTENTS OF SELECTED MINERAL RAW MATERIALS IN 

 ALL SEA WATER AND IN A THREE-KILOMETER CRUST OF THE LITHOSPHERE 



Source: Ocean Engineering, Vol. 4, Pt. 1 , 1966. Sea water: E.D. Goldberg, "Marine Geochemistry," Annual Review of 

 Physical Chemistry, pp. 29-48; 1961 lithosphere: K. Rankama and Th. G. Sahama, Geochemistry (Chicago: University 

 of Chicago Press, 1950). 



Based on following masses: oceans: 



1.42 X 10^* metric tons; lithosphere crust: 1.24 x 10 metric tons. 



lighter minerals that are carried away. The min- 

 erals must previously have undergone extensive 

 weathering and erosion from their original position 

 within igneous and metamorphic rocks. Because 

 the ocean floor lacked sufficient weathering and 

 erosion few if any placer deposits should have 

 originated on it. Instead, placers on the ocean 

 floor should be extensions of well-known ones on 

 land- such as the gold of Alaska, the tin of Malaya 

 and Cornwall, and the diamonds of Southwest 

 Africa. Placers are unrelated to the composition of 

 their substrate, but they occur only near their 

 primary igneous or metamorphic source rocks. 



Most of the placers of submerged beach and 

 drowned river valley types were formed during the 

 Ice Ages when sea level was lowered as much as 

 137 to 160 meters below the present sea level ^'^ 

 because so much ocean water was in the form of 

 ice in continental glaciers. Owing to the cyclic 

 nature of the Ice Ages and the intervening warm 

 interglacial periods, a series of beaches and exten- 

 sions of stream channels were formed in some 



W. L. Donn, W. R. Farraid, and M. Ewing, "Pleis- 

 tocene Ice Volumes and Sea Level Lowering," Journal of 

 Geology, Vol. 70, No. 2, 1962, pp. 206-214. 



VIH02 



