18 • Marine Minerals: Exploring Our New Ocean Frontier 



The military value of some EEZ data 

 might require restrictions on access and 

 use of certain information for national 

 security reasons. 



information about the magnetic field and may be 

 used offshore to map sediments and rocks contain- 

 ing magnetite and other iron-rich minerals. Both 

 of these technologies are also used for oil and gas 

 exploration. Data can be collected rapidly by mov- 

 ing vessels and stored in retrievable form. 



Other technologies may also be used to explore 

 the EEZ. Some, like many electrical techniques, 

 are proven technologies for land-based exploration 

 which have been adapted for ocean use, but have 

 not been vi'idely tested in the marine environment. 

 Induced polarization, for example, has potential for 

 locating titanium placer deposits and for perform- 

 ing rapid, real-time, shipboard analyses of core 

 samples. Nuclear techniques may also prove use- 

 ful for identifying such minerals as phosphorite, 

 monazite, and zircon that emit radiation. 



When the focus of attention narrows to prospec- 

 tive targets of interest on the seafloor, direct visual 

 observation is often useful. Manned submersibles 

 and/or remotely operated undersea vehicles (ROVs), 

 similar to those used for locating the Titanic in 

 1986, may come into play. Remotely operated 

 cameras capable of observing, transmitting, and 

 recording photographic images have proved valu- 

 able exploration tools. 



Direct sampling of seabed minerals for assess- 

 ment presents special problems. In some cases, it 

 is possible (as has been done with the research sub- 

 mersible Alvin to recover limited samples of seabed 

 minerals using manned submersibles or ROVs). 

 A number of devices have been developed to re- 

 trieve a sample of unconsolidated sediment, but few 

 are capable of extracting undisturbed samples that 

 reflect the mineral concentrations contained in the 



Photo credit: Emory Kristof and Alvin M. Ctiandler, National Geograptiic 



The manned submersible /4/Wn provided researchers 



with their first face-to-face encounter with the 



formation of metallic sulfide minerals on the 



oceanfloor in the late 1970s. 



seabed deposit. Many of the sediment coring de- 

 vices were designed for scientific use, and few are 

 capable of economically and efficiently recovering 

 the large number of samples that are needed to ac- 

 curately determine the commercial feasibility of a 

 marine mineral deposit and to delineate a mine site. 



Quantitative sampling of hard-rock deposits, 

 e.g., ferromanganese crusts and polymetallic sul- 

 fides, is economically infeasible with existing tech- 

 nology. While large drill ships (e.g., the Joides 

 Resolution) used in the Ocean Drilling Project or 

 those used by the offshore petroleum industry, are 

 capable of drilling and extracting cores from hard 

 basaltic rock, their cost is prohibitive for extensive, 

 high-density sampling of the kind needed to assess 

 a mineral deposit. It may prove easier to develop 

 a practical sampling device for thin ferromanganese 

 crusts than for the thicker, less regular, polymetallic 

 sulfides. 



