Water depth dependence of Mn-nodule features in the NE equatorial Pacific

Abstract

Korean contract Mn-nodule field in the NE equatorial Pacific is composed of seven sectors showing average water depths of 4,513 &#8211 5,025 m. Of the various factors controlling the property of Mn-nodule, it seems that water depth has potential linkage to chemical composition, shape and abundance of nodule. To clarify such possibility, we review more than 20 years research data in the one of the northern sectors (hereafter KR1) where shows a stark contrast in water depth. High-resolution seabed mapping clearly separates a northern part from a deeper southern part, cutting across in the mid of the KR1. In terms of nodule occurrence, manganese nodules in the deeper north are comparatively larger (2&#8211 4 cm) with rough surface (t-type) and discoidal shape (D-type), while those in the south are generally small (<2 cm) with smooth surface (s-type) and irregular shape (I-type). In addition, the nodules in the north have higher metal contents including Cu, Mn and Ni. Such connections of water depths to nodule occurrence and metal contents are commonly observed in the Korea licensed Pacific nodule fields.tential linkage to chemical composition, shape and abundance of nodule. To clarify such possibility, we review more than 20 years research data in the one of the northern sectors (hereafter KR1) where shows a stark contrast in water depth. High-resolution seabed mapping clearly separates a northern part from a deeper southern part, cutting across in the mid of the KR1. In terms of nodule occurrence, manganese nodules in the deeper north are comparatively larger (2&#8211 4 cm) with rough surface (t-type) and discoidal shape (D-type), while those in the south are generally small (<2 cm) with smooth surface (s-type) and irregular shape (I-type). In addition, the nodules in the north have higher metal contents including Cu, Mn and Ni. Such connections of water depths to nodule occurrence and metal contents are commonly observed in the Korea licensed Pacific nodule fields.