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Middle Valley, Bent Hill Massive Sulfide

Name Alias(es): 
Site 856, Middle Valley
ODP Mound
MGDS_FeatureID lowest in hierarchy: 
Maximum Temperature: 
Max Temperature Category: 
Location on map: 
National Jurisdiction: 
Maximum or Single Reported Depth (mbsl): 
Minimum Depth (mbsl): 
Tectonic setting: 
Full Spreading Rate (mm/a): 
Volcano Number (if applicable): 
Host Rock: 
MORB, minor E-MORB, sediment-hosted
Deposit Type: 
PMS, polymetallic massive sulfides
Notes on Vent Field Description: 
In Version 3.4 of the Vents Database we combined Bent Hill and ODP Mound into a single listing; a centred position has been provided by Ocean Network Canada based on their observations; hole 856H is located about halfway between 856A at the summit of Bent Hill and 1035H which was given in previous versions of the Vents Database as the position of ODP Mound; ODP Mound (Hole 1035H) is located ~300 m south of the Bent Hill MS deposit; note: Butterfield et al. (1994) say Bent Hill is active with temp. 265 C - this was measured at Lone Star vent at ODP Mound; sulfide deposits within turbiditic sediments in a buried rift adjacent to Endeavour Ridge (several sulfide outcrops up to 100 m in diameter); Ocean Drilling Program (ODP) hole 856H penetrates through the massive sulfide; prior to ODP 169 drilling 1996, Lone Star was the only known vent; Shiner Bock vent confirmed 1998; Spire observed after 1998; Cruse et al. abstract GSA 2003: "ODP Mound is presently venting ~270°C degree fluids at several locations. In July 2000 hydrothermal fluids were collected at Shiner Bock and Spire vents, and ODP Hole 1035H that started venting high-temperature fluids following drilling in 1996."
Notes Relevant to Biology: 
Year and How Discovered (if active, visual confirmation is listed first): 
1990 HOV Alvin, 1985 deposits only
Discovery References (text): 
(Middle Valley SMS deposits only) EE Davis et al. (1987) Massive sulfides in a sedimented rift valley, northern Juan de Fuca Ridge. Earth Planet Sci Let 82: 49–61.
Ames, D.E., et al., 1993. Mineralogy and geochemistry of active and inactive chimneys and massive sulfide, Middle Valley, northern Juan de Fuca Ridge: an evolving hydrothermal system. Can. Mineral., 31:997-1024
Other References (text): 
Butterfield et al., (1994) Geochemistry of hydrothermal vent fluids from Middle Valley, Juan de Fuca Ridge. In: Mottl, M.J., et al. (Eds.), Proc. ODP, Sci. Results, vol. 139, pp. 395–410
Cruse, AM and Seewald, JS (2006) Geochemistry of low-molecular weight hydrocarbons in hydrothermal fluids from Middle Valley, northern Juan de Fuca Ridge. Geochim Cosmochim Acta 70(8): 2073-2092.
Teagle and Alt (2004) Hydrothermal Alteration of Basalts beneath the Bent Hill Massive Sulfide Deposit, Middle Valley, Juan de Fuca Ridge. Econ. Geol. 99: 561-584.