X-ray Computed Tomography Analysis of Ferromanganese Nodule Nuclei from the Western North Pacific Ocean: Insights into Their Origins

Ferromanganese nodule nuclei are considered crucial to the formation and distribution of nodules. However, because it is difficult time-consuming study ferromanganese nuclei, few studies have been performed, despite large number samples. Here, we analyzed 934 nodules from abyssal seafloor around Minamitorishima Island (western North Pacific Ocean) using X-ray computed tomography (CT). Based on CT (describing absorption in Hounsfield units, HU), classified as Type I (>1800 HU) or II (<1800 HU). Additionally, some had characteristic conical shapes (Type I-C) distinct other I-O). chemical compositions determined by microfocus fluorescence analyses selected samples, identified I-C, I-O, fish teeth, hard rocks (volcanic rock, ironstone, phosphorite), sediments, respectively. These nucleus types were observed sufficient quantities at all dive sites that conclude them be typical area. Fish-tooth rarest sites, whereas sediment dominated most suggesting their significance for understanding origin Hard-rock only three probably originated seamounts.