@article {Syverson2017,
	title = {{Fe isotope fractionation between chalcopyrite and dissolved Fe during hydrothermal recrystallization: An experimental study at 350 {\textdegree}C and 500 bars}},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {200},
	year = {2017},
	pages = {87{\textendash}109},
	abstract = {Equilibrium Fe isotope fractionation between chalcopyrite and dissolved Fe was determined in acidic chloride-bearing fluid at 350 {\textdegree}C and 500 bars. The study utilized deformable gold-cell technology, which allowed time-series sampling of solution during chalcopyrite recrystallization and isotope exchange. A key element of the experimental design involved the addition of anomalous dissolved 57Fe to an on-going experiment as a means of determining the degree and rate of isotope exchange. Taking explicit account of imposed chemical and isotopic mass balance constraints of Fe in fluid and mineral (chalcopyrite) reservoirs, these data indicate that no more than 1000 h is required for the isotopically anomalous dissolved Fe reservoir to exchange completely with the coexisting chalcopyrite. The experimental calibration of the rate of Fe isotope exchange for the $δ$57Fe-spiked experiment provides critical insight for the time necessary to achieve Fe isotope exchange in two non-spiked, but otherwise identical experiments. The Fe isotope data indicate that the equilibrium fractionation between chalcopyrite and dissolved Fe, $Δ$56FeCpy-Fe (aq), at 350 {\textdegree}C is small, 0.09 {\textpm} 0.17{\textperthousand} (2$\sigma$), and is in good agreement with recent theoretical equilibrium predictions. Owing to the apparent rate of Fe isotope exchange at 350 {\textdegree}C, it is likely that chalcopyrite formed at high temperature deep-sea vents (black smoker systems) achieves isotopic equilibrium, and effectively records the Fe isotopic composition of the coexisting end-member hydrothermal fluid. Comparison of the experimental mineral{\textendash}fluid equilibrium fractionation factors with conjugate chalcopyrite and dissolved Fe pairs sampled from high temperature hydrothermal vent systems at Axial Caldera and Main Endeavour Field (Juan de Fuca Ridge) are in agreement with this inference. The experimental data were further used to determine the mineral{\textendash}mineral equilibrium Fe isotope fractionation between pyrite-chalcopyrite, $Δ$56FePyr-Cpy, at 350 {\textdegree}C by combining previously determined pyrite-Fe2+(aq) equilibrium fractionation data with chalcopyrite-Fe2+(aq) from this study. The empirically determined $Δ$56FePyr-Cpy value, 0.90 {\textpm} 0.34{\textperthousand} (2$\sigma$), is consistent with theoretical predictions, and when coupled with mineral{\textendash}fluid Fe isotope fractionation systematics and experimentally determined exchange rates, helps to delineate processes of sulfide mineralization in hydrothermal systems.},
	keywords = {HOV Alvin (Human Occupied Vehicle)},
	doi = {10.1016/j.gca.2016.12.002},
	author = {Syverson, D D and Luhmann, A J and Tan, C Y and Borrok, D M and Ding, K and Seyfried, W E}
}
@article {Tan2016,
	title = {{Development and Application of a New Mobile pH Calibrator for Real-Time Monitoring of pH in Diffuse Flow Hydrothermal Vent Fluids}},
	journal = {Marine Technology Society Journal},
	volume = {50},
	number = {2},
	year = {2016},
	pages = {37{\textendash}47},
	abstract = {In situ measurement of pH in diffuse flow hydrothermal vent fluids is necessary to investigate the feedback between geochemical and biochemical processes. Accurate pH determination has been unusually challenging owing to temperature and pressure effects that place severe constraints on the performance of a wide variety of pH sensor systems. In this paper, we describe a newly developed mobile pH calibrator (MpHC), which makes use of In situ calibration protocols that enhance the accuracy of pH measurement and monitoring on the ocean floor at deep-sea hydrothermal vents. The MpHC combines the physically robust and highly sensitive iridium solid-state pH electrode with a flow control system to perform 2-point calibration with on-board pH buffer solutions. The small size and novel design of the sensor probe allow more effective access to seafloor hydrothermal vent fluids and their associated sulfide structures and biological communities. The MpHC is capable of In situ deployment by submersible via ICL (inductively couple link) communication around hydrothermal vents at pressures and temperatures up to 45 MPa and 100 degrees C, respectively. In this paper, we also present results of In situ calibration methods used to correct the standard potential and slope (mV/pH) of the solid-state electrode for temperature effects. The MpHC has been deployed most recently using the submersible Alvin during cruise AT26-17 to Axial Seamount and Main Endeavour Field, Juan De Fuca Ridge in the NE Pacific. With In situ calibration functionality, the MpHC offers the prospect of more successful longer-term measurements in keeping with power availability provided by cabled seafloor observatories coming online in the NE Pacific.},
	keywords = {HOV Alvin (Human Occupied Vehicle)},
	author = {Tan, C Y and Ding, K and Seyfried, W E}
}
@article {Gulmann2015,
	title = {{Bacterial diversity and successional patterns during biofilm formation on freshly exposed basalt surfaces at diffuse-flow deep-sea vents}},
	journal = {Frontiers in Microbiology},
	volume = {6},
	year = {2015},
	pages = {901},
	abstract = {Many deep-sea hydrothermal vent systems are regularly impacted by volcanic eruptions, leaving fresh basalt where abundant animal and microbial communities once thrived. After an eruption, microbial biofilms are often the first visible evidence of biotic re-colonization. The present study is the first to investigate microbial colonization of newly exposed basalt surfaces in the context of vent fluid chemistry over an extended period of time (4{\textendash}293 days) by deploying basalt blocks within an established diffuse-flow vent at the 9{\textdegree}50' N vent field on the East Pacific Rise. Additionally, samples obtained after a recent eruption at the same vent field allowed for comparison between experimental results and those from natural microbial re-colonization. Over 9 months, the community changed from being composed almost exclusively of Epsilonproteobacteria to a more diverse assemblage, corresponding with a potential expansion of metabolic capabilities. The process of biofilm formation appears to generate similar surface-associated communities within and across sites by selecting for a subset of fluid-associated microbes, via species sorting. Furthermore, the high incidence of shared operational taxonomic units over time and across different vent sites suggests that the microbial communities colonizing new surfaces at diffuse-flow vent sites might follow a predictable successional pattern.},
	keywords = {HOV Alvin (Human Occupied Vehicle)},
	doi = {10.3389/fmicb.2015.00901},
	author = {Gulmann, L K and Beaulieu, S E and Shank, T M and Ding, K and Seyfried, W E and Sievert, S M}
}
@article {Seyfried2015,
	title = {{The Lost City hydrothermal system: Constraints imposed by vent fluid chemistry and reaction path models on subseafloor heat and mass transfer processes}},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {163},
	year = {2015},
	pages = {59{\textendash}79},
	abstract = {Since the first reported discovery of the Lost City hydrothermal system in 2001, it was recognized that seawater alteration of ultramafic rocks plays a key role in the composition of the coexisting vent fluids. The unusually high pH and high concentrations of H2 and CH4 provide compelling evidence for this. Here we report the chemistry of hydrothermal fluids sampled from two vent structures (Beehive: \~{}90{\textendash}116 {\textdegree}C, and M6: \~{}75 {\textdegree}C) at Lost City in 2008 during cruise KNOX18RR using ROV Jason 2 and R/V Revelle assets. The vent fluid chemistry at both sites reveals considerable overlap in concentrations of dissolved gases (H2, CH4), trace elements (Cs, Rb, Li, B and Sr), and major elements (SO4, Ca, K, Na, Cl), including a surprising decrease in dissolved Cl, suggesting a common source fluid is feeding both sites. The absence of Mg and relatively high concentrations of Ca and sulfate suggest solubility control by serpentine{\textendash}diopside{\textendash}anhydrite, while trace alkali concentrations, especially Rb and Cs, are high, assuming a depleted mantle protolith. In both cases, but especially for Beehive vent fluid, the silica concentrations are well in excess of those expected for peridotite alteration and the coexistence of serpentine{\textendash}brucite at all reasonable temperatures. However, both the measured pH and silica values are in better agreement with serpentine{\textendash}diopside{\textendash}tremolite-equilibria. Geochemical modeling demonstrates that reaction of plagioclase with serpentinized peridotite can shift the chemical system away from brucite and into the tremolite stability field. This is consistent with the complex intermingling of peridotite and gabbroic bodies commonly observed within the Atlantis Massif. We speculate the existence of such plagioclase bearing peridotite may also account for the highly enriched trace alkali (Cs, Rb) concentrations in the Lost City vent fluids. Additionally, reactive transport modeling taking explicit account of temperature dependent rates of mineral dissolution and precipitation clarifies the feedback between permeability, heat loss, and changes in the dissolved Si of the vent fluids. Assuming both the Beehive and M6 vent fluids were sourced at similar subseafloor conditions (tremolite buffered at 200 {\textdegree}C), model results indicate loss of approximately 30{\%} Si upon cooling to \~{}150 {\textdegree}C during upflow. However, Si concentrations remained largely conservative with continued cooling to lower temperatures owing to unfavorable reaction kinetics. While consistent with the Beehive endmember composition, these results fail to explain the relative Si depletion in the lower temperature M6 fluids. Thus, it may be that more robust kinetic models for silicates are needed to accurately account for the mechanism and rate of silica removal in the unusually high pH of the Lost City vent fluids.},
	keywords = {HOV Alvin (Human Occupied Vehicle)},
	doi = {10.1016/j.gca.2015.04.040},
	author = {Seyfried, W E and Pester, N J and Tutolo, B M and Ding, K}
}
@article {Pester2011,
	title = {{A new Fe/Mn geothermometer for hydrothermal systems: Implications for high-salinity fluids at 13{\textdegree}N on the East Pacific Rise}},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {75},
	number = {24},
	year = {2011},
	pages = {7881{\textendash}7892},
	abstract = {Field and experimental investigations demonstrate the chemistry of mid-ocean ridge hydrothermal vent fluids reflects fluid{\textendash}mineral reaction at higher temperatures than those typically measured at the seafloor. To account for this and, in turn, be able to better constrain sub-seafloor hydrothermal processes, we have developed an empirical geothermometer based on the dissolved Fe/Mn ratio in high-temperature fluids. Using data from basalt alteration experiments, the relationship; T ({\textdegree}C)~=~331.24~+~112.41*log[Fe/Mn] has been calibrated between 350 and 450~{\textdegree}C. The apparent Fe{\textendash}Mn equilibrium demonstrated by the experimental data is in good agreement with natural vent fluids, suggesting broad applicability. When used in conjunction with constraints imposed by quartz solubility, associated sub-seafloor pressures can be estimated for basalt-hosted systems. As an example, this methodology is used to interpret new data from 13{\textdegree}N on the East Pacific Rise, where high-temperature fluids both enriched and depleted in chloride (339{\textendash}646~mmol/kg), relative to seawater, are actively venting within a close proximity. Accounting for these variable salinities, active phase separation is clearly taking place at 13{\textdegree}N, yet the fluid Fe/Mn ratios and the silica concentrations suggest equilibration at temperatures less than those coinciding with the two-phase region. These data show the chloride-enriched fluid reflects the highest temperature and pressure (\~{}432~{\textdegree}C, 400~bars) of equilibration, consistent with circulation near the top of the inferred magma chamber. This is in agreement with the elevated CO2 concentration relative to the chloride-depleted fluids. The noted temperature derived from the Fe/Mn geothermometer is higher than the critical temperature for a fluid of equivalent salinity. This carries the important implication that, despite being chloride-enriched relative to seawater, these fluids evolved as the vapor component of even higher salinity brine.},
	keywords = {HOV Alvin (Human Occupied Vehicle)},
	issn = {0016-7037},
	doi = {10.1016/j.gca.2011.08.043},
	url = {http://dx.doi.org/10.1016/j.gca.2011.08.043},
	author = {Pester, N J and Rough, M and Ding, K and Seyfried, W E}
}
@inbook {Pester2008,
	title = {{The chemistry of diffuse-flow vent fluids on the Galapagos Roft (86 degrees W) : temporal vaiability and subseafloor phase equilibria controls}},
	booktitle = {Magma to microbe : modeling hydrothermal processes at ocean spreading centers},
	series = {Geophysical Monograph},
	number = {178},
	year = {2008},
	pages = {123{\textendash}144},
	publisher = {American Geophysical Union},
	organization = {American Geophysical Union},
	address = {Washington, DC},
	keywords = {HOV Alvin (Human Occupied Vehicle)},
	isbn = {0875904432},
	doi = {10.1029/178GM07},
	url = {http://dx.doi.org/10.1029/178GM07},
	author = {Pester, N J and Butterfield, D A and Foustoukos, D I and Roe, K K and Ding, K and Shank, T M and Seyfried, W E},
	editor = {Lowell, R P}
}
@article {Ding2005,
	title = {{The in situ pH of hydrothermal fluids at mid-ocean ridges}},
	journal = {Earth and Planetary Science Letters},
	volume = {237},
	number = {1-2},
	year = {2005},
	pages = {167{\textendash}174},
	keywords = {HOV Alvin (Human Occupied Vehicle)},
	issn = {0012-821X},
	doi = {10.1016/j.epsl.2005.04.041},
	url = {http://dx.doi.org/10.1016/j.epsl.2005.04.041},
	author = {Ding, K and Seyfried, W E and Zhang, Z and Tivey, M K and Von Damm, K L and Bradley, A M}
}
@article {Seyfried2003,
	title = {{Chemistry of hydrothermal vent fluids from the Main Endeavour Field, northern Juan de Fuca Ridge: Geochemical controls in the aftermath of June 1999 seismic events}},
	journal = {Journal of Geophysical Research},
	volume = {108},
	number = {B9},
	year = {2003},
	pages = {Article no. 2429},
	keywords = {HOV Alvin (Human Occupied Vehicle)},
	issn = {0148-0227},
	doi = {10.1029/2002JB001957},
	url = {http://dx.doi.org/10.1029/2002JB001957},
	author = {Seyfried, W E and Seewald, J S and Berndt, M E and Ding, K and Foustoukos, D}
}
@article {Ding2001,
	title = {{In situ measurement of dissolved H (sub 2) and H (sub 2) S in high-temperature hydrothermal vent fluids at the Main Endeavour Field, Juan de Fuca Ridge}},
	journal = {Earth and Planetary Science Letters},
	volume = {186},
	number = {3-4},
	year = {2001},
	pages = {417{\textendash}425},
	keywords = {HOV Alvin (Human Occupied Vehicle)},
	issn = {0012-821X},
	doi = {10.1016/S0012-821X(01)00257-6},
	url = {http://dx.doi.org/10.1016/S0012-821X(01)00257-6},
	author = {Ding, K and Seyfried, W E and Tivey, M K and Bradley, A M}
}
