Sea Technology

AUG 2017

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Page 11 of 76 August 2017 / st 11 Research Center for Marine Environmental Sciences at Bre- men University has developed the seafloor drill rig MeBo (acronym for Meeresboden-Bohrger├Ąt, German for seafloor drill rig) to drill up to 80 m into the seafloor. Design Criteria The Remotely Operated Coring System (ROCS) was de- signed to provide core samples from a lighter setup with lower cost, complexity and risk compared to the systems described above. Design criteria of the ROCS specified that it had to be deployable from the heavy work-class ROVs (100 to 300 hp) widely used in support of offshore oil and gas production worldwide. These vehicles can provide re- search platforms of opportunity for mineral exploration when fitted with a core sampling drill. This class of ROV has sufficient size and power to provide the reactive mass (in-water weight combined with downward thrust) to permit drilling an 80-mm-diameter hole (75-mm core sample) into a seabed that can range from very soft material to competent rock, while concurrently supplying auxiliary power for the drilling operation. The ROCS is relatively compact and can be mounted on many different ROV models. The serial data channel in the ROV telemetry system is used to control drill- ing functions from the ROV control station on the ship. The ROV used was an electrohydraulic model, but with some modification this core drilling system can also be used on direct-drive electric units. MarMine Project The MarMine project is a multidisciplinary research project aimed at assessing and developing new knowledge about exploration and exploitation technologies and de- fining the mineralogical properties of typical seafloor ma- rine mineral deposits along the Arctic Mid-Ocean Ridge (AMOR). Environmental sustainability is also addressed by the project. A multidisciplinary cruise was set up for the AMOR area August to September 2016. The offshore construction ves- sel Polar King fitted with two work-class ROVs, an offshore crane and a Kongsberg HUGIN AUV was utilized. The cruise lasted for 20 days. To be able to test the equipment and to sample both active and inactive vent sites, the project focused on two known sites: Loki Cas- tle and Mohn's Treasure, both discovered and described by the University of Bergen. The main objectives of the MarMine cruise were to: obtain geologi- cal samples for mineral char- acterization and assessment of mining and mineral processing potential; test new exploration technologies and methods; pro- vide a baseline analysis of the biological systems present on active and inactive hydrother- mal vents; and explore areas of particular interest based on previous analysis of the resource potential. Loki Castle is a site of known active hydrothermal vent- ing where sulphide-carrying fluids are discharged from chimneys as black smoker fluids. The fluids have been pre- viously measured to a temperature of about 320┬░ C. The vent field consists of multiple chimneys located on the top of two mounds at approximately 2,400-m depth. They are found on the top of an Axial Volcanic Ridge (AVR) that rises about 1,300 m above the valley floor. According to the Uni- versity of Bergen, the mineral content in the chimneys con- sists mostly of chalcopyrite, sphalerite, pyrite and pyrrhotite. Both basalt, chimney fragments, unconsolidated and oxi- dized material are present on the site. Several-hundred kilos of surface material were sampled by the ROV manipulators. The Mohn's Treasure area is located southwest of Loki Castle on the western flank of the spreading ridge. A dredge operation conducted in 2002 brought up sediments con- taining pyrite and chimney fragments with fluid channels; however, no seawater anomalies were detected in the area, indicating that the deposits stem from an extinct site. The area of Mohn's Treasure is characterized by a high and steep (Top) ROCS drilling system mounted on ROV. (Bottom) Driller console window.

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