Hydrothermal Vents Along the Spike Segment of the Southern EPR (17 15-40'S)
1997 American Geophysical Union Fall Meeting
Within the Spike Survey we located 14 active high-T sites with black- or white-smoker chimneys, plus 17 additional sites where black or white smoke plumes were present, for a total of 31 high-T sites along a 48 km length of the EPR. By comparison, a 1989 Argo I survey of the fast-spreading (11 cm/yr) EPR at 9 30'-54'N revealed 25 sites with smokers or smoke along a 44 km length of ridge axis (Haymon et al., 1991). Many more inactive chimneys were observed at 9 -10 N than in the Spike Survey area, suggesting that more frequent or recently extensive axial eruptions have destroyed or buried inactive chimneys along the Spike ridge segment. Chimneys in the Spike Area tend to be isolated, small structures, with no more than 5 spindly spires, indicating ages of less than a few years (based on chimney growth rates after the 1991 eruption at EPR 9 45'-52'N).
Vents and animal communities are grouped into 3 fields, each ~9 km in length, and separated by ~7 km-long gaps. Their distribution and dimensions may reflect 4th order ridge segmentation and the pattern of shallow axial magma supply. Animal communities and active vents are not symmetrically dispersed about the magma cupola, but rather are more abundant along strike to the south. Some black smokers are not associated with visible vent fauna. The locations of some, but not all, of the smokers are controlled by identifiable eruptive fissures.