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Name Alias(es): 
Trans-Atlantic Geotraverse
TAG Mound
26 N, MAR
MGDS_FeatureID lowest in hierarchy: 
Vent Sites: 
Alvin zone
Mir zone
ODP 957M
ODP 957D
Shimmering Mound
Maximum Temperature: 
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: 
Deposit Type: 
PMS, polymetallic massive sulfides
Notes on Vent Field Description: 
TAG is within a larger hydrothermal field that extends over an area of at least 5 km x 5 km and consists of presently active low and high temperature zones, as well as a number of relict deposits; Klinkhammer et al. (1986): "In July 1985 the first high-temperature, hydrothermal vents ever discovered on the MAR were found at 26°N (TAG)"; Rona and Speer (1989): "hydrothermally active mound up to 250 m wide and 50 m high", "the first high-temperature hydrothermal field found at a slow-spreading oceanic ridge"; drilled in 1994 on ODP Leg 158; (the following site descriptions provided by P. Rona, pers. comm., 2010): TAG active high-temperature sulfide mound, active, 26 08.21’ N, 44 49.57’ W, depth 3635-3670 m, 1985 camera-temperature tows and water chemistry, first hydrothermal field found in the Atlantic and on any slow-spreading ocean ridge, P.A. Rona, et al., (1986); TAG Alvin zone, inactive, 26 09.54’ N (26.159) to 26 10.62’ N (26.177), 44 48.50’ W (44.808) to 44 48.89’ W (44.815), depth 3410-3600 m, zone of discontinuous sulfide outcrop, metalliferous sediment, Fe-Mn oxide staining, and four large inactive massive sulfide mounds up to 200 m in diameter, 1984-1988 camera tows and side-scan sonar reported in P. A. Rona, et al., (1993a) and 1993 HOV Alvin dive series reported in P.A. Rona, et al., (1996); TAG Alvin mound, inactive, 26 09.54’ N, 44 48.89’ W, depth 3512-3540 m, 1984-1988 camera tows and 1993 HOV Alvin dives reported in P.A. Rona, et al., (1996); TAG Mir zone, patchy diffuse flow and seepage, 26 08.70’ N, 44 48.40’ W, depth 3430-3575 m, 1984-1988 camera tows and 1991 Mir dive series reported in P.A. Rona, et al., (1993b); TAG Shinkai massive sulfide mound, inactive, 26 09.52’ N, 44 49.15’ W, depth 3545-3615 m, P.A. Rona, et al., (1998); TAG Shimmering mound, active low-temperature diffuse flow, 26 10.25’ N, 44 48.88’ W, depth 3436-3504 m, P.A. Rona, et al., (1998); Fujioka et al. (1998) describing Shimmering Mound: "an active low-temperature hydrothermal system was the northern end of the Alvin zone. Clear water is discharging at temperatures tens of degrees C...and sustaining a biota"
Notes Relevant to Biology: 
Alvinocaridid shrimp, Bythograeid crabs, Zoarcids, Mytilid mussels, Polynoids
Year and How Discovered (if active, visual confirmation is listed first): 
1985 towed camera and temperature anomaly; 1986 submersible Alvin
Discovery References (text): 
Rona, P.A. et al (1986) Black smokers, massive sulphides and vent biota at the Mid-Atlantic Ridge. Nature 321: 33-37
Klinkhammer et al. (1986) Manganese geochemistry near high-temperature vents in the Mid-Atlantic Ridge rift valley. Earth and Planetary Science Letters 80: 230-240
Rona, PA and Speer, KG (1989) An Atlantic hydrothermal plume: Trans-Atlantic Geotraverse (TAG) area, mid-Atlantic ridge crest near 26°N. Journal of Geophysical Research, Volume 94, Issue B10, p. 13879-13893.
Other References (text): 
[Rona et al 1984 JGR 89: 11365-11377 for tentative ID of vent biota prior to the 1986 paper
P. A. Rona, et al., 1993a, Active and relict sea-floor hydrothermal mineralization at the TAG hydrothermal field, Mid-Atlantic Ridge, Economic Geology, 88: 1989-2017
P.A. Rona, et al., (1993b), Relict hydrothermal zones at the TAG hydrothermal field, Mid-Atlantic Ridge 26 N, 45 W, Journal of Geophysical Research, 98: 9715-9730]
Herzig et al. (1995) Ocean Drilling Program reveals the subsurface nature of the TAG hydrothermal mound. InterRidge News 4(1): 11-14
[P.A. Rona, et al., 1996, Heat flow and mineralogy of TAG relict high-temperature hydrothermal zones: Mid-Atlantic Ridge 26 N, 45 W, Geophysical Research Letters, 23: 3507-3510
P.A. Rona, et al., 1998, An active low-temperature mound and a large sulfide mound found in the TAG hydrothermal field, Mid-Atlantic Ridge 26 N, 45 W (abstract), Eos, Transactions American Geophysical Union, 79(45): F920]
Fujioka et al. (1998) Hydrothermal processes and architecture of the slow-spreading MAR at TAG and Rainbow hydrothermal fields and Dante's Dome megamullion site (MODE'98 Leg 2). InterRidge News 7(2): 18-23.