Hydrothermal vent precipitates: A study of temporal and geographic variations in black smoker particles and chimneys from 9-10 degres north, east Pacific rise

In order to examine how hydrothermally-produced minerals reflect evolution of a vent system with time, we used the submersible Alvin to collect sulfide/sulfate chimneys and buoyant plume particles from 10 vents in the East Pacific Rise axial summit caldera at sites between 9 degrees 51 minutes North and 9 degrees 29 minutes North. These vents ranged in age from mature vents associated with sizable mineral deposits and sedimented lava flows (D and K) to vents initiated during the observed eruption in 1991 (Bio9, P, A, L, Le.1). Sampling was accomplished over a five-year span. Elemental composition of the particulate material reveals the apparent geological control on the nature of the particle assemblages. Notable intrafield variation in Cu/Fe and Zn/Fe molar ratios across 4th order ridge segments suggests that geographic variation reflects differences in the ages of individual segments and corresponding maturity of their hydrothermal systems. Immature vents in the eruption area exhibit a greater abundance of Cu-, Fe-, and Zn-sulfide minerals whereas older more mature vents away from the 1991 eruption area have oxide-dominated particle assemblage. The geographic trends are observed only in particles collected close to the vents, with signal diminishing with increased seawater entrainment.; A five-year time series of chimney chemistry and mineralogy shows that mineralogical and chemical changes are rare over the time period. However, evolution of the vents over longer time periods (decades) is reflected in the differences in chimney mineral content and morphology between vents formed on new lava flows within the eruption area, and vents located outside the eruption area on older lavas. Individual vents do not change much after the initial perturbing effects of diking and eruption, but differences between the vent sites reflect longer-term effects of maturity.