Preliminary Results of KORDI's Research Cruises for Submarine Hydrothermal Sulfides in the Lau Basin in 2004 and 2005

Abstract

Since hydrothermal vent areas were known as the best natural laboratory to research about the evolution of the oceanic crust, the genesis of mineral deposits, and the origin of life, etc, the Korea Ocean Research and Development Institute (KORDI) has been carrying out a submarine hydrothermal sulfide project as a long-term government R & D program which is supported by the Ministry of Maritime Affairs and Fisheries (MOMAF). KORDI had conducted two research cruises in the Eastern Lau Spreading Center, Fonualei Rift and Spreading Center (FRSC), and Tofua Volcanic Arc in the Lau Basin in 2004 and 2005 using KORDI's R/V Onnuri. We plan to continue our survey in this area until 2010, hopefully with the deep-sea unmanned underwater vehicle (UUV) which is being developed by KORDI. The UUV consist of an underwater launcher named “Henuvy” and a remotely operated vehicle (ROV) named “Hemire” and are similar to Jason II from WHOI, Victor 6000 from IFREMER, and Kaiko from JAMSTEC. During our 2004 and 2005 research cruises, new hydrothermal plumes were discovered along the axis of FRSC and off-axis active caldera in the northeastern Lau basin. Hydrothermal tracers in water column, such as light transparency, Mn, CH4, and ATP, indicate that at least four different sites of active hydrothermal vents exist along the axis of FRSC and off-axis active caldera. Volcanic rocks from the axis of FRSC are tholeiitic basalt and basaltic andesite, while those from off-axis active caldera are dacite. These rocks are enriched in large ion lithophile (LIL) elements and depleted in high field strength (HFS) elements, which suggests incorporation of arc component during the magma genesis. Sediment core samples from two hydrothermal vent sites in the axis of FRSC contain enriched layers of hydrothermal elements, such as Mn, Cu, Zn, Pb, As, Ga, Ba, and Tl. Fragments of hydrothermal chimneys were also sampled from one of these hydrothermal vent sites. They mainly consist of barite and spha