Exploring ultradeep hydrothermal vents in the Cayman Trough by ROV

The 110-kilometer-long Mid-Cayman Spreading Center (MCSC), located within the Cayman Trough in the Caribbean Sea, is the world’s deepest seafloor spreading rift. Reaching depths beyond 6,000 meters, the MCSC hosts the deepest hydrothermal vents known. This ultradeep volcanic rift was explored by developing and operating the Hydraulic Benthic Interactive Sampler (HyBIS) ROV. The vehicle yielded the discovery of two hydrothermal vent fields on the rift floor: one at 5,000 meters depth and another in the central MCSC located on the side of a large seamount and forming the western flank of the rift. With their contrasting styles of fluid venting, sulfide mineralization, geological setting and host-rock interaction, the differences between these two sites indicate that depth and basement rock type may significantly affect the metal content of hydrothermal seafloor massive sulfide deposits.