Ferromanganese micronodules have been found on Georges Bank, off the U.S. northeast coast, distributed throughout the surficial sediments within an area about 125 km long and at least 12 km wide. These coarse, sand-sized concretions have precipitated from metal-rich interstitial waters and contain many of the textural and structural features common to other neritic nodules. Most of the nodules have accreted around detrital grains, and X-ray powder diffraction analyses indicate the presence of geothite and vernadite (δ-MnO2) in the ferromanganese layers. Chemical analyses of the micronodules, when compared with similar data on deep-sea manganese nodules, reveal lower Mn/Fe ratios, significantly higher concentrations of V and As, comparable values of Mo, and an order of magnitude less of Co, Ni, Ce and most other metals.
Poppe, L. J., R. F. Commeau, J. A. Commeau, F. T. Manheim, and P. J. Aruscavage. 1984. "Ferromanganese micronodules from the surficial sediments of Georges Bank." Journal of Marine Research 42, (2). https://elischolar.library.yale.edu/journal_of_marine_research/1727