ABSTRACT

Box corer (BC) sampling is a well-known method in exploration of deep-sea polymetallic (manganese) nodules. This paper presents the results of monitoring the behavior of BC in a 2018 survey cruise in the Clarion–Clipperton Zone, Central Pacific Ocean. In particular, the sensor data on the depth and inclination of the BC body obtained by an offline inclinometer provided direct information on the BC's irregular behaviors in case of unsuccessful sampling. The data of inclinometer are consistent with those in other monitoring data, such as pinger or wire tension, and thus can be useful to improve equipment maintenance and operation during deployment.

INTRODUCTION

Polymetallic nodules (also referred to as manganese nodules or nodules) on the seafloor are spherical to ellipsoidal manganese-oxide concretions ranging from a few to 10 cm in diameter. They contain metals such as copper, cobalt, and nickel, which are considered important mineral resources (e.g., Morgan, 2017; Hein et al., 2020; Cronan, 2022). The Clarion–Clipperton Zone (CCZ) in the Central Pacific is known to yield particularly large amounts of manganese nodules and has been the object of research cruises by countries and institutions around the world. Exploration activities for marine mineral resources in the open sea are managed by the International Seabed Authority (ISA) established under the United Nations Convention on the Law of the Sea (e.g., Lodge et al., 2014), recent activities in the open sea are aimed for not only resource estimation but also collection of environmental baseline data and testing mining machines (e.g., Amon et al, 2016; Jones et al, 2017; Sharma, 2020; Parianos et al., 2021; Kang and Liu, 2021; Muñoz-Royo et al., 2022). This paper reports the results of monitoring and sensor data on Box Corer (BC) sampling in a manganese nodules survey cruise conducted by Deep Ocean Resources Development, Co., Ltd. (DORD), which is under an exploration contract with the ISA.

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