Ferromanganese crust deposits occurring on seamounts and the flanks of oceanic islands within the U.S. Exclusive Economic Zone (EEZ) have been identified as being a potentially significant domestic Source for the strategic metals cobalt and manganese. A major problem encountered by researchers is the lack of efficient survey tools for these deposits. A better understanding and assessment of these deposits requires collection of detailed information on their distribution and the variability of their occurrence, thickness and chemical composition. This information can only be obtained through collection of large numbers of precisely located samples. This paper reviews the design and development of a multisample crust coring device that can recover up to 30 full thickness samples of ferromanganese crust in a single lowering. The system is ideally suited for closely spaced grid sampling of a given deposit in order to provide information on the thickness of the deposit and sample material for ore grade analysis. The sampler utilizes a series of thirty percussion coring guns with short, tethered coring projectiles. The system is triggered by a bottom sensing device and the firing and sequencing of the core guns is controlled by a microprocessor and battery housed in a pressure housing on the sampling vehicle. Initial design testing and prototype design has' been completed and a prototype sampler has been fabricated. The system has been successfully deployed at sea and a limited number of samples have been recovered. Development of the sampler is continuing with the addition of a variable rate pinger to provide real time information on the operational status of the system and a camera system to provide hindsight information on the sampling environment. INTRODUCTION: With the creation of the U. S. 200 mile offshore Exclusive Economic Zone (EEZ) in 1983, marine ferromanganese oxide crust deposits have become a potential major domestic source for the strategic metals cobalt and manganese. This has created a need for appropriate survey tools to conduct large scale reconnaissance as well as detailed resource evaluations of these deposits. Methods currently employed in the study of ferromanganese crusts are limited to video or photographic surveys and dredging. Photographic surveys are useful in determining the presence or absence of crust deposits, but provide minimal information on crust thickness and no compositional data. Dredging has the major drawbacks of being time consuming, often unsuccessful, and non-site specific along the dredge path. It is used only because no alternative tools exist which are effective for sampling these deposits. Because of a lack of suitable sampling devices, the volume of ferromanganese crust data and samples is inadequate to develop a detailed understanding of the factors controlling their genesis and distribution. In response to the rising need for more efficient survey tools for the investigation of ferromanganese crust deposits, Analytical Services Company has undertaken the development of a multisample crust coring system.
