Ch. 4— Technologies for Exploring the Exclusive Economic Zone • 159 



A few small samples of crust have been retrieved 

 using standard deep-sea dredges. As these dredges 

 are pulled along the bottom, they are able to dis- 

 lodge chunks of the outcrop or gather already dis- 

 lodged material; however, techniques and technol- 

 ogy for precise, controlled sampling have yet to be 

 developed.^* USGS has identified several needs in 

 quantitative crust sampling and, through its Small 

 Business Innovative Research program, has begun 

 several feasibility studies to develop sampling tools. 



As an aid in selecting sampling sites and in quan- 

 tifying the volume of crust in a given area, a de- 

 vice that can measure crust thickness is an impor- 

 tant need. Deepsea Ventures, Inc., has completed 

 a conceptual study for such a device for USGS.^^ 

 The goal is to develop a tool to measure crust thick- 

 ness continuously and in real-time. Conceptually, 

 a very-high-frequency acoustic-reflection profiler 

 able to detect the crust surface and the interface 

 between crust and host rock would be mounted 

 aboard a sled and, with a video camera, towed 20 

 to 25 centimeters off the seafloor. A continuous sig- 

 nal would be sent to the surface ship via the tow 

 cable. An important design consideration is the very 

 rough terrain in which some cobalt crusts are found. 

 Current design criteria call for the device to oper- 

 ate over relatively smooth areas with less than a 

 20° slope. Although it will not be able to operate 

 on slopes steeper than 20°, it is assumed that, at 

 least initially, any crust mining that does occur will 

 be done in relatively flat areas. 



For quantitative sampling, two types of coring 

 devices have been proposed and currently are being 

 designed. Deepsea Ventures has developed concepts 

 for a special sampling tool for taking an undisturbed 

 sample suitable for studying the engineering prop- 

 erties of crust and underlying rock.^" This corer 

 would be capable of cutting a disc-shaped core 56 

 centimeters (22 inches) in diameter by 23 centi- 

 meters (9 inches) thick. The corer and a video cam- 

 era would be mounted on a tripod anchored to the 



"D.S. Cronan, H. Kunzendorf, et al., "Report of the Working 

 Group on Manganese Nodules and Crusts," Marine Minerals: Ad- 

 vances in Research and Resource Assessment, P.G. Teleki, et al. (eds.) 

 (Dordrecht, Holland: D. Reidel Publishing Co., 1987), NATO AST 

 Series, p. 24. 



"'W. Siapno, Consultant, OTA Workshop on Site-Specific Tech- 

 nologies for Exploring the Exclusive Economic Zone, Washington, 

 DC, July 16, 1986. 



'"Ibid, 



sea bottom while the core is being cut. This type 

 of corer would not be useful for detailed mapping 

 of a deposit because the tripod must be lowered, 

 positioned, and raised for each core cut, a process 

 that would take more than 2 hours in 1 ,500 meters 

 of water. 



A second coring device more appropriate for 

 reconnaissance sampling (and perhaps also for 

 proving a mine site) has been designed and built 

 by Analytical Services, Inc. (figure 4-14).^' The de- 

 vice is a percussion coring sampler that is designed 



"J. Toth, Analytical Services, Inc., OTA Workshop on Site-Specific 

 Technologies for Exploring the Exclusive Economic Zone, Washing- 

 ton, DC, July 16, 1986. 



Figure 4-14.— Prototype Crust Sampler 



Sliding 

 column " 



Battery and 



electronics 



housing 



Trigger 

 assembly 



Gimbal 

 assembly 



Frame - 



Firing 

 plate 



Coring devices such as this, designed to be quick and inex- 

 pensive, will be needed for quantitative sampling of crusts 



SOURCE: Analytical Services, Inc., Cardiff, CA. 



