@article {Soule2012,
	title = {{CO2 variability in mid-ocean ridge basalts from syn-emplacement degassing: Constraints on eruption dynamics}},
	journal = {Earth and Planetary Science Letters},
	volume = {327{\textendash}328},
	year = {2012},
	pages = {39{\textendash}49},
	abstract = {Basaltic glasses produced during mid-ocean ridge (MOR) eruptions display a wide range of dissolved CO2 concentrations with respect to equilibrium saturation at their eruption depth. This variability is thought to reflect the dynamics of magma ascent and emplacement, with rapid ascent and depressurization leading to supersaturated conditions and slower ascent resulting in equilibrium saturation. In this study we examine a suite of samples from the 2005{\textendash}06 eruption of the East Pacific Rise (EPR), collected at {\~{}}~200~m intervals along two well-defined flow pathways within a single seafloor eruption to examine syn-emplacement degassing, using measurements of vesicularity, crystallinity, volatile contents, and helium. This new data set is unique because flow pathways of individual MOR lava flows have rarely been mapped and have never been systematically sampled. Here we show that a large range in dissolved CO2 concentrations exists within this single eruption that nearly spans that observed in tens of flows measured along this portion of the EPR crest. This lava flow experienced equilibrium degassing of dissolved CO2 from supersaturated conditions at the vent (and persisting over the first 750~m of flow) toward equilibrium with seafloor pressures along a {\~{}}~2.5~km-long flow path. This was accompanied by an increase in vesicularity and characteristic bubble radius along the flow, indicating the importance of bubble growth by diffusion for degassing. Nearly constant total helium concentrations (melt~+~vesicles) indicate that no bubbles were lost during emplacement. With a model of diffusion-controlled bubble growth constrained by observations from the samples along the largest flow lobe of the eruption, we calculate minimum ascent rates of 0.15~m/s, and {\textendash} for this portion of the eruption {\textendash} an eruption duration of {\~{}}~30~h and flow rates from 0.02 to 0.12~m/s. This study represents the first quantitative assessment of eruption dynamics using volatiles in a mid-ocean ridge lava flow.},
	keywords = {ROV Jason (Remotely Operated Vehicle)},
	issn = {0012-821X},
	doi = {10.1016/j.epsl.2012.01.034},
	url = {http://dx.doi.org/10.1016/j.epsl.2012.01.034},
	author = {Soule, S A and Nakata, D S and Fornari, D J and Fundis, A T and Perfit, M R and Kurz, M D}
}
@mastersthesis {Nakata2010,
	title = {{Syn-eruptive degassing of a single submarine lava flow : constraints on MORB CO2 variability, vesiculation, and eruption dynamics}},
	volume = {M.S.},
	year = {2010},
	pages = {63},
	school = {Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution},
	type = {phd},
	address = {Cambridge, MA and Woods Hole, MA},
	abstract = {Mid-ocean ridge basalts (MORBs) exhibit a wide range of CO2 concentrations, reflecting saturation to supersaturation (and rarely undersaturation) relative to their emplacement depths. In this study, we explore the mechanisms of CO2 degassing and the implications this has for estimating the advance rates and durations of seafloor eruptions. We present dissolved volatile concentrations (mainly of CO2 and H2O) and vesicle size distributions (VSDs) for a unique suite of MORB glasses collected at the East Pacific Rise, {\~{}}9{\textdegree} 50' N. These MORB glasses were collected at {\~{}}200 m intervals along an across-axis track over a single flow pathway within the recently emplaced 2005-06 eruption boundaries; systematic sample collection provides one of the first opportunities to characterize intra-flow geochemical and physical evolution during a single eruption at a fast-spreading ridge. Compared to measurements of MORB volatiles globally, dissolved H2O concentrations are relatively uniform (0.10 - 0.16 weight percent), whereas dissolved CO2 contents exhibit a range of concentrations (154 - 278 ppm) and decrease with distance from the EPR axis (i.e., eruptive vent). Ion microprobe analyses of dissolved volatiles within the MORB glasses suggest that the magma erupted supersaturated (pressure equilibrium with 920 - 1224 mbsf) and in near-equilibrium with the melt lens of the axial magma chamber ({\~{}}1250 - 1500 mbsf), and degassed to near equilibrium (299 - 447 mbsf) with seafloor depths over the length of the flow. The decrease in CO2 concentrations spans nearly the full range of dissolved CO2 contents observed at the EPR and shows that the varying degrees of volatile saturation that have been observed in other MORB sample suites may be explained by degassing during emplacement. Vesicularity (0.1 - 1.2{\%}) increases with decreasing dissolved CO2 concentrations. We use vesicle size distributions (VSDs){\textemdash}vesicle sizes and number densities{\textemdash}to quantify the physical evolution of the CO2 degassing process. VSDs suggest that diffusion of CO2 into preexisting vesicles, and not nucleation of new vesicles, is the dominant mechanism of increasing CO2 in the vapor phase. We also use VSDs, along with estimates of vesicle growth rates, to constrain emplacement time of the 2005-06 eruption to {\textless}{\~{}}24 hours and to resolve variations in advance rate with downflow distance.},
	keywords = {HOV Alvin (Human Occupied Vehicle), ROV Jason (Remotely Operated Vehicle)},
	doi = {10.1575/1912/3933},
	url = {http://hdl.handle.net/1912/3933},
	author = {Nakata, D S}
}
