Evaluation of erosional processes and determining if atolls have aided the formation of polymetallic nodules Caroline Islands, Federated States of Micronesia’s Exclusive Economic Zone

Abstract

This project aimed to identify the role nearshore sources of metallics play in the formation of polymetallic nodules in the abyssal planes of the Western Equatorial Pacific. Polymetallic nodules also known as ferromanganese nodules are valuable seafloor features that contain high levels of rare earth metals, of which most notable are manganese and cobalt. The incentive to mine these nodules for their metallics has increased due to the advancement of technology, and demand. The site location for this study was within the exclusive economic zone of the Federated States of Micronesia, and specifically Nam2 Atoll. Three sediment grab samples were collected and an analysis of the historical undercurrents in the region were conducted. X ray fluorescence spectroscopy was performed on the sediment samples. Two locations contained detectable levels of manganese and one contained cobalt. A particle settling analysis conducted on the sediment grains using Stokes law, calculated the distance of possible travel using the historical undercurrent to model the trajectory of the grains. A conservative time needed to reach the atoll, utilizing only the undercurrents, is 71.2 days. The largest grains were calculated to settle in 19 days while the smallest could stay suspended for several millennia. This study site has had evidence of turbidity currents since the Miocene, and by comparing studies it was determined that a turbidity current from Nam2 could reach approximately 400 km to sites on the abyssal plain. Thus, via a turbidity current, all grain sizes collected could reach the abyssal plains. This study suggests that Co-rich/Mn-rich sediment found at Nam2 Atoll within a wide range of grain sizes, could aid in the formation of polymetallic nodule, (PMN). This would be made possible through transport via undercurrents for smaller sizes and the effects of a large sediment gravity flow for larger grain sizes. These findings potentially increase the locations where mineable amounts of polymetallic nodules could be found globally.