@article {Fornari2012,
	title = {{The East Pacific Rise Between 9 degrees N and 10 degrees N: Twenty-Five Years of Integrated, Multidisciplinary Oceanic Spreading Center Studies}},
	journal = {Oceanography},
	volume = {25},
	number = {1},
	year = {2012},
	month = {mar},
	pages = {18{\textendash}43},
	publisher = {OCEANOGRAPHY SOC},
	address = {ROCKVILLE; P.O. BOX 1931, ROCKVILLE, MD USA},
	abstract = {The East Pacific Rise from {\~{}}~9{\textendash}10{\textdegree}N is an archetype for a fast-spreading mid-ocean ridge. In particular, the segment near 9{\textdegree}50{\textquoteright}N has been the focus of multidisciplinary research for over two decades, making it one of the best-studied areas of the global ridge system. It is also one of only two sites along the global ridge where two historical volcanic eruptions have been observed. This volcanically active segment has thus offered unparalleled opportunities to investigate a range of complex interactions among magmatic, volcanic, hydrothermal, and biological processes associated with crustal accretion over a full magmatic cycle. At this 9{\textdegree}50{\textquoteright}N site, comprehensive physical oceanographic measurements and modeling have also shed light on linkages between hydrodynamic transport of larvae and other materials and biological dynamics influenced by magmatic processes. Integrated results of high-resolution mapping, and both in~situ and laboratory-based geophysical, oceanographic, geochemical, and biological observations and sampling, reveal how magmatic events perturb the hydrothermal system and the biological communities it hosts.},
	keywords = {HOV Alvin (Human Occupied Vehicle), ROV Jason (Remotely Operated Vehicle)},
	issn = {1042-8275},
	doi = {10.5670/oceanog.2012.02},
	author = {Fornari, D J and Von Damm, K L and Bryce, Julia G and Cowen, J P and Ferrini, Vicki and Fundis, A and Lilley, M D and Luther, G W and Mullineaux, L S and Perfit, M R and Meana-Prado, M F and Rubin, K H and Seyfried, W E and Shank, T M and Soule, S A and Tolstoy, M and White, S M}
}
@article {Pester2012,
	title = {{Subseafloor phase equilibria in high-temperature hydrothermal fluids of the Lucky Strike Seamount (Mid-Atlantic Ridge, 37{\textdegree}17{\textquoteright}N)}},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {90},
	year = {2012},
	pages = {303{\textendash}322},
	abstract = {As part of an integrated study conducted at the Lucky Strike Seamount (Mid-Atlantic Ridge, 37{\textdegree}17'N) in 2008, gas-tight sampling devices were used to collect high-temperature (\~{}300~{\textdegree}C) hydrothermal fluids issuing from sulfide structures distributed throughout the vent field located in the summit depression. Compared with previous observations from 1993 to 1997, the most substantial changes in vent fluid compositions are dramatically increased CO2 concentrations (\~{}5{\texttimes}, up to 133~mmol/L) and the observation of vent fluids enriched in dissolved chloride relative to seawater. Combined with an increase in $δ$13CCO2$δ$13CCO2 values by \~{}4{\textperthousand} in 2008, the elevated CO2 indicates replenishment of the magmatic heat source and may be indicative of a recent magmatic event. The additional supporting fluid chemistry is, however, similar to that of the previous sampling intervals, necessitating a reassessment of the subseafloor controls on vent fluid chemistry at Lucky Strike in the context of recently obtained geophysical data that provides the depth/extent of a steady-state magma chamber. Two-phase behavior is indicated by the chloride variability in the vent fluids; and comparison with experimental data for the associated chloride-dependent partitioning of minor/trace elements suggests the possibility of a similar source fluid for all the vent structures, while limiting the likelihood of shallow phase separation and subseafloor mixing for the hydrothermal end-members. A recently calibrated Fe/Mn geothermometer indicates minimum subseafloor equilibration temperatures of 350{\textendash}385~{\textdegree}C. However, constraints imposed by dissolved Si/Cl in conjunction with geophysical observations are consistent with peak reaction conditions at temperatures of 430{\textendash}475~{\textdegree}C and pressures near the top of the axial magma chamber (\~{}410{\textendash}480~bars), where magmatic CO2 becomes entrained in the circulating fluids. The distance between the magma chamber and the seafloor at Lucky Strike is substantially greater than at most faster spreading ridges; and we propose the resulting increased residence time in the up-flow zone leads to the re-equilibration of temperature sensitive transition metals at conditions less extreme than those associated with peak reaction. Agreement between experimental data, thermodynamic model calculations, and dissolved concentrations of Fe, Cu, Zn, H2, and H2S in the Lucky Strike fluids reinforce the hypothesis of pH-redox equilibria for transition metals at relatively oxidizing conditions and temperatures predicted by the empirical Fe/Mn geothermometer. In-situ pH measurements of the high-temperature fluids exiting the seafloor are also consistent with the model calculations.},
	keywords = {ROV Jason (Remotely Operated Vehicle)},
	doi = {10.1016/j.gca.2012.05.018},
	url = {http://dx.doi.org/10.1016/j.gca.2012.05.018},
	author = {Pester, N J and Reeves, E P and Rough, M E and Ding, K and Seewald, J S and Seyfried, W E}
}
@article {Seyfried2011,
	title = {{Vent fluid chemistry of the Rainbow Hydrothermal System (36 degrees N, MAR): Phase equilibria and in-situ pH controls on subseafloor alteration processes}},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {75},
	number = {6},
	year = {2011},
	pages = {1574{\textendash}1593},
	abstract = {The Rainbow hydrothermal field is located at 36{\textdegree}13.8'N{\textendash}33{\textdegree}54.15'W at 2300~m depth on the western flank of a non-volcanic ridge between the South AMAR and AMAR segments of the Mid-Atlantic Ridge. The hydrothermal field consists of 10{\textendash}15 active chimneys that emit high-temperature (\~{}365~{\textdegree}C) fluid. In July 2008, vent fluids were sampled during cruise KNOX18RR, providing a rich dataset that extends in time information on subseafloor chemical and physical processes controlling vent fluid chemistry at Rainbow. Data suggest that the Mg concentration of the hydrothermal end-member is not zero, but rather 1.5{\textendash}2~mmol/kg. This surprising result may be caused by a combination of factors including moderately low dissolved silica, low pH, and elevated chloride of the hydrothermal fluid. Combining end-member Mg data with analogous data for dissolved Fe, Si, Al, Ca, and H2, permits calculation of mineral saturation states for minerals thought appropriate for ultramafic-hosted hydrothermal systems at temperatures and pressures in keeping with constraints imposed by field observations. These data indicate that chlorite solid solution, talc, and magnetite achieve saturation in Rainbow vent fluid at a similar pH(T,P) (400~{\textdegree}C, 500~bar) of approximately 4.95, while higher pH values are indicated for serpentine, suggesting that serpentine may not coexist with the former assemblage at depth at Rainbow. The high Fe/Mg ratio of the Rainbow vent fluid notwithstanding, the mole fraction of clinochlore and chamosite components of chlorite solid solution at depth are predicted to be 0.78 and 0.22, respectively. In situ pH measurements made at Rainbow vents are in good agreement with pH(T,P) values estimated from mineral solubility calculations, when the in situ pH data are adjusted for temperature and pressure. Calculations further indicate that pH(T,P) and dissolved H2 are extremely sensitive to changes in dissolved silica owing to constraints imposed by chlorite solid solution-fluid equilibria. Indeed, the predicted correlation between dissolved silica and H2 defines a trend that is in good agreement with vent fluid data from Rainbow and other high-temperature ultramafic-hosted hydrothermal systems. We speculate that the moderate concentrations of dissolved silica in vent fluids from these systems result from hydrothermal alteration of plagioclase and olivine in the form of subsurface gabbroic intrusions, which, in turn are variably replaced by chlorite~+~magnetite~+~talc~{\textpm}~tremolite, with important implications for pH lowering, dissolved sulfide concentrations, and metal mobility.},
	keywords = {ROV Jason (Remotely Operated Vehicle)},
	issn = {0016-7037},
	doi = {10.1016/j.gca.2011.01.001},
	url = {http://dx.doi.org/10.1016/j.gca.2011.01.001},
	author = {Seyfried, W E and Pester, N J and Ding, K and Rough, M}
}
