PMS, polymetallic massive sulfides
Notes on Vent Field Description:
small vent fields with active sulfide deposits and low-temperature Fe oxide and silica chimneys; [first documented eruption on MOR] basaltic fissure eruption between 1983 and 1987, 1986 and 1987 megaplume; http://www.pmel.noaa.gov/vents/cleft_site.html; separated from low-temperature vents to south by a gap in venting from 44 54.5'N to 44 56.5'N; low-temperature vents associated with this field extend to at least 45 03'N; Baker and Hammond (1992): "The absence of temperature elevations in Crane et al.'s  1982 and 1983 data from the northern end of Cleft suggests that the 1986 megaplume may have substantially rejuvenated this vent field"; note Ed Baker separates Pipe Organ from the other sites into its own vent field listing
Notes Relevant to Biology:
Year and How Discovered (if active, visual confirmation is listed first):
1987 camera/CTD tows discovered low-temperature vents; 1988 submersible Alvin sampled low-temperature vents; 1990 submersible Alvin discovered black smoker
Discovery References (text):
Embley et al., Geology, 19, 771-775, 1991, Geology of the northern Cleft segment, Juan de Fuca Ridge: Recent lava flows, sea-floor spreading, and the formation of megaplumes.
Other References (text):
(plume only) Baker and Hammond (1992) Hydrothermal Venting and the Apparent Magmatic Budget of the Juan de Fuca Ridge. J. Geophys. Res. 97(B3): 3443-3456
Butterfield and Massoth, J. Geophys. Res. 99, 4951-4968, 1994, Geochemistry of north Cleft segment vent fluids: Temporal changes in chlorinity and their possible relation to recent volcanism
Koski, R.A. et al. (1994) Compositions, growth mechanisms, and temporal relations of hydrothermal sulfide-sulfate-silica chimneys at the northern Cleft segment, Juan de Fuca Ridge. JGR 99(B3): 4813-4832.