PMS, polymetallic massive sulfides (active and inactive)
Notes on Vent Field Description:
two large active sulfide deposits (nesca, sesca) within turbiditic sediments in the buried axial (up to 250 m explored dimensions); 220 C alkali-rich vents and low temperature venting; Nine holes were drilled in the NESCA area in 1996 on ODP Leg 169; Sites 1037 (reference hole) and 1038 drilled during ODP Leg 169; Zierenberg et al. (2001): "Mapping with Tiburon confirmed that the extent of hydrothermal venting at NESCA decreased dramatically since 1988.", "Venting at the seafloor does not seem to have been affected by drilling in the hydrothermal field."; http://marine.usgs.gov/fact-sheets/gorda/; Alvin dives 2033-2042 in 1988
Notes Relevant to Biology:
tubeworms (Ridgeia); Zierenberg et al. (2001): "Formerly extensive colonies of Ridgeia had vanished leaving no trace of their presence."
Year and How Discovered (if active, visual confirmation is listed first):
1988 submersible Alvin; 1986 dredge and photographs did not confirm activity
Discovery References (text):
JL Morton et al. (1987) Geophys Res Lett Volume 14, Issue 7, p. 769-772, Volcanism and massive sulfide formation at a sedimented spreading center, Escanaba trough, Gorda ridge, northeast Pacific Ocean.
Other References (text):
Baker et al., Deep Sea Res. 34, 1461-1476, 1987, Evidence for high-temperature hydrothermal venting on the Gorda Ridge, northeast Pacific Ocean
[Zierenberg et al., Econ. Geol., 88, 2069-2098, 1993, Genesis of massive sulfide deposits on a sediment-covered spreading center, Escanaba Trough, southern Gorda Ridge]
Zierenberg et al. (2001) Decline of a Hydrothermal Vent Field - Escanaba Trough 12 Years Later. AGU Fall Meeting abstract #V12D-1009
Gieskes et al. (2002) Hydrothermal geochemistry of sediments and pore waters in Escanaba Trough—ODP Leg 169. Applied Geochemistry 17: 1435-1456
Koski et al. (2002) Hydrothermal Tar Mounds in Escanaba Trough, Southern Gorda Ridge. American Geophysical Union, Fall Meeting 2002, abstract #V72A-1293
Von Damm et al. (2005) The Escanaba Trough, Gorda Ridge hydrothermal system: Temporal stability and subseafloor complexity. Geochimica et Cosmochimica Acta 69: 4971-4984.