Temperature measurements during initiation and growth of a black smoker chimney

Abstract

BLACK smoker chimneys are hollow spires formed by mineral deposition at sea-floor hydrothermal vent sites. They grow in two stages: formation of a sulphate-dominated wall (stage I), followed by precipitation of sulphide minerals on the inner side, and in pore spaces, of the wall (stage II)^1,2. Here we present the results of an in situ 46-day experiment which allows direct observation of stage I growth processes by monitoring wall and fluid temperatures. The position and thickness of stage I chimney walls can change on short timescales, and are controlled by the dynamics of fluid flow both during³ and after initial wall emplacement. The temperature in the main flow remained stable at 353±2°C throughout the experiment, including the period during which the chimney wall was constructed. Six thermocouples, however, recorded maximum temperatures between 365 and 405 °C, which are significantly higher than most exit temperatures documented previously⁴. These latter observations bear on the question of the maximum temperatures attainable in sea-floor hydrothermal systems (refs 4–9, J. R. Delaney, manuscript in preparation).