Chapter 4 



Technologies for Exploring the 

 Exclusive Economic Zone 



INTRODUCTION 



The Exclusive Economic Zone (EEZ) is the 

 largest piece of "real estate" to come under the 

 jurisdiction of the United States since acquisitions 

 of the Louisiana Purchase in 1803 and the purchase 

 of Alaska in 1867. The EEZ remains largely un- 

 explored, both in the Lewis and Clark sense of gain- 

 ing general knowledge of a vast new territory and 

 in the more detailed sense of assessing the location, 

 quantity, grade, or recoverability of resources. This 

 chapter identifies and describes technologies for ex- 

 ploring this vast area, assesses current capabilities 

 and limitations of these technologies, and identi- 

 fies future technology needs. 



The goal of mineral exploration is to locate, iden- 

 tify, and quantify mineral deposits, either for sci- 

 entific purposes (e.g., better understanding their 

 origin) or for potential commercial exploitation. 

 Detailed sampling of promising sites is necessary 

 to prove the commercial value of deposits. Obvi- 

 ously, it would be impractical and costly to sam- 

 ple the entire EEZ in the detail required to assess 

 the commercial viability of a mineral deposit. For- 

 tunately, this is not necessary as techniques other 

 than direct sampling can provide many indirect 

 clues that help researchers or mining prospectors 

 narrow the search area to the most promising sites. 



Clues to the location of potential offshore mineral 

 accumulations can be found even before going to 

 sea to search for them. The initial requirements of 

 an exploration program for the EEZ are a thorough 

 understanding of its geological framework and of 

 the geology of adjacent coastal areas. In some in- 

 stances, knowledge of onshore geology may lead 

 directly to discoveries in adjacent offshore areas. 

 For example, a great deal is currently known about 

 the factors responsible for the formation of offshore 

 heavy mineral deposits and gold placers. These fac- 

 tors include onshore sources of the minerals, trans- 

 port paths, processes of concentration, and pres- 



ervation of the resulting deposit.' In contrast, 

 relatively little is known about the genesis of co- 

 balt crusts or massive sulfides. Although a thorough 

 understanding of known geology and current geo- 

 logical theory may not lead directly to a commer- 

 cial discovery, some knowledge is indispensable for 

 devising an appropriate offshore exploration 

 strategy. 



Rona and others have used the concept of "clos- 

 ing range to a mineral deposit" to describe an ex- 

 ploration strategy for hydrothermal mineral depos- 

 its.^ With some minor modifications this strategy 

 may be applicable for exploration of many types 

 of offshore mineral accumulations. It is analogous 

 to the use of a zoom lens on a camera which first 

 shows a large area with little detail but then is ad- 

 justed for a closeup view to reveal greater detail in 

 a much smaller area. The strategy of closing range 

 begins with regional reconnaissance. Reconnais- 

 sance technologies are used to gather information 

 about the "big picture. ' ' While none of these tech- 

 niques can provide direct confirmation of the ex- 

 istence, size, or nature of specific mineral depos- 

 its, they can be powerful tools for deducing likely 

 places to focus more attention. As knowledge is ac- 

 quired, exploration proceeds toward increasingly 

 more focused efforts (see table 4-1), and the explo- 

 ration technologies used have increasingly specific 

 applications. Technologies that provide detailed in- 

 formation can be used more efficiently once recon- 

 naissance techniques have identified the promising 



'H.E. Clifton and G. Luepke, "Heavy Mineral Placer Deposits 

 of the Continental Margin of Alaska and the Pacific Coast States," 

 Geology and Resource Potential of the Continental Margin of West- 

 em North America and Adjacent Ocean Basins — Beaufort Sea to Baja 

 California, American Association of Petroleum Geologists, Memoir 

 43, in press, 1986, p. 2 (draft). 



^P.A. Rona, "Exploration for Hydrothermal Mineral Deposits at 

 Seafloor Spreading Centers," Marine Mining, Vol. 4, No. 1, 1983, 

 pp. 20-26. 



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