Deep-Sea Laser-Induced Breakdown Spectroscopy and its Application to Hydrothermal Mineral Surveys in the Okinawa Trough

Laser-induced breakdown spectroscopy (LIBS) is a form of atomic emission spectroscopy that uses a focused laser-pulse to create a plasma of excited material that can be used to determine the multi-elemental composition of targets in situ. In this work, the authors describe the development of a 3000m depth rated LIBS instrument and its deployments from a remotely operated vehicle (ROV) at depths of more than 1000m. Exemplary measurements of the multi-element composition of both seawater and mineral deposits made at an active hydrothermal vent field in the Okinawa trough will be presented and methods developed to process the measurements made by the instrument will be discussed. This is the first application of LIBS to oceanographic studies and the technique is currently one of the few methods available to perform in situ multi-element analysis underwater at oceanic pressures. Through integration with platforms such as underwater vehicles, drilling systems and subsea observatories, it is hoped that this technology can contribute to more efficient scientific surveys of the deep-sea environment.