CRITICAL MINERAL CONTENTS OF DEEP OCEAN PHOSPHORITES AND FERROMANGANESE CRUSTS IN THE BLAKE PLATEAU AND SOUTHERN CALIFORNIA BORDERLAND OFFSHORE OF THE UNITED STATES

The total area of offshore territory within the Exclusive Economic Zone of the United States is larger than its entire land area, and within these regions deep ocean minerals occur that contain critical minerals and rare earth elements. Two such regions include the Blake Plateau off the Atlantic coast and the Southern California Borderland off the Pacific coast, both of which host ferromanganese minerals and phosphorites. These regions were sampled and preliminarily characterized in terms of mineral resource potential over the last ~50 years, however, most studies reported concentrations of only select elements. For ferromanganese minerals in Blake Plateau, average concentration values for manganese, iron, cobalt, nickel, and copper were emphasized, and for phosphorites in both regions, only phosphorus, calcium, and major elements were typically reported. The exception is ferromanganese crusts in the Southern California Borderland for which a few samples from within the Borderland and the seamounts just outside were characterized for a full suite of more than 50 elements. Analogous to reinvestigating known terrestrial ore bodies for additional minerals, expanding geochemical analyses of previously characterized marine mineral systems contributes to the inventory of critical and rare earth minerals. Here I will present new geochemical data, including critical mineral concentrations, for recently recovered samples as well as recharacterized archive samples from both regions. While work remains to determine distribution and tonnages for these ferromanganese and phosphorite mineral occurrences, critical mineral data will provide an update to previous investigations of their mineral resource potential and expand critical mineral resource considerations offshore of the United States.