Journalartikel

Jahr der Veröffentlichung: 1991

Seiten: 303-306

Zeitschrift: Geology

Bandnummer: 19

Heftnummer: 4

ISSN: 0091-7613

Verlag: Geological Society of America

Abstract: 
The submersible Nautile completed 22 dives during the Nautilau cruise (R/V Nadir, April 17-May 10, 1989) for a detailed investigation of the southern Lau basin near Tonga. The objective of the scientific team from France, Germany, and Tonga was to understand the process of sea-floor ore formation associated with hydrothermal circulation along the Valu Fa back-arc ridge behind the Tonga-Kermadec trench. The four diving areas, between lat 21-degrees-25'S and 22-degrees-40'S in water approximately 200 m deep, were selected on the basis of results from cruises of the R/V Jean Charcot and R/V Sonne. The Nadir cruise provided proof of hydrothermal activity-in all four areas, over more than 100 km-as indicated by the widespread occurrence of hydrothermal deposits and by heat flow, conductivity, and temperature measurements near the sea bottom. The most spectacular findings were high-temperature white and black smokers and associated fauna and ore deposits. Hydrothermal water chemistry and sulfide composition data presented here indicate that this hydrothermal field is very different from the hydrothermal fields in oceanic ridges. This difference is seen in the water chemistry of the hydrothermal fluid (pH = 2 and high metal content) and the chemical composition of sulfides (enrichment in Ba, As, and Pb).