An Experimental Study of Water and Carbon Dioxide Solubilities in Mid-Ocean Ridge Basaltic Liquids. Part I: Calibration and Solubility Models

Abstract

INTRODUCTIONSu baerial magmas solidify at a pressure of -1 bar, but the pressure on submarine magmas ranges from near I bar to several hundred bars, depending on the water depth at which they erupt. Even over this small pressure range, the vesicularity and vesicle-gas composition of submarine magmas of constant bulk composition can change dramatically, reflecting the large differences in volume between gaseous a nd melt species, the large compressibility of the gas phase at these low pressures, and the increasing (but different) solubilities of all gaseous species with pressure in this pressure range. Thus, the well-known negative corr elation between eruption depth a nd vesicularity of subm arine magmas reflects the degassing of magmas at progressively lower pressures under conditions where the exsolving vapor is unable to escape fully from the m agma (e.g. Moore, 1965, (!) Oxford University Press 1995 1970Moore & Schilling, 1973). Likewise, the different solubilities of the major (e.g. C02, H20, S) and minor (e.g. rare gases) volatile species are expected (though not yet observed) to lead to a strong dependence of the composition of the vapor in the vesicles on depth (e.g. Moore, 1965Moore, , 1970Jambon et al., 1985;Gerlach, 1986; ]ambon et al., 1986; Zhang & Zindler, 1989; Bottinga & Javoy, 1990b). Similarly, it is thought that differing solubilities of oxidized and reduced gaseous species can result in systematic changes in the oxidation state of iron and sulfur in erupting magmas as a function of the degree and depth of degassing (e.g. Sa to, 1978;Mathez, 1984; Carmichael & G hiorso, 1986;Christie et al., 1986;Wallace & Carmichael, 1992;Nilsson & Peach, 1993). In view of the importance of the exsolution of a vapor phase from submarine magmas in . understanding their vesicle contents, their eruptive style, aspects of their chemistry, and ultimately the chemistry of the atmosphere and ocean (e.g. Javoy et al., 1982;Des Marais, 1985; Marty & ]ambon, 1987;Gerlach, 1989; Zhang & Zindler, 1989, it is surprising how little is known about the behavior of volatile components in these systems in the pressure range over which these magmas are erupted. For example, only recently has the solubility of carbon dioxide, the major component of vesicle gases in mid-ocean ridge basalt (MORB) (Killingley & Muenow, 1975;Moore et al., 1977;Delaney et al., 1978;]ambon & Zimmermann, 1987), been measured in MORB melt by experiment (Stolper & Holloway, 1988;Shilobreyeva & Kadik, 1989; Mattey, 1991; Pan et al., 1991 ;Pawley et al., 1992;Trull et al. , 1992) . Water is even more abundant than carbon dioxide in most MORB glasses, but we know of no measurements of the solubility of water in MORB liquids at eruptive conditions, although water solubilities have been measured at higher pressures ( 1-10 kbar) in other basaltic compositions (Khitarov et al., 1959;Hamilton et al., 1964;Kadik et al., 1971 ). Kadik et al. (1972} reported mixed C0 2 and H 2 0 solubilities in basaltic melts at 1-3 kbar, but their experiments did not extend to...

CO2 content beneath northern Iceland and the variability of mantle carbon

“…The correlation of CO 2 with nonvolatile trace elements demonstrates that these melt inclusions were trapped before the magma became saturated in a CO 2 -rich vapor phase. The maximum CO 2 concentrations indicate minimum trapping depths of 8-10 km for the initiation of magma crystallization, using the H 2 O-CO 2 solubility model of Dixon et al (1995). This is consistent with CO 2 -trace element correlations indicating that the melts had not degassed significantly at the time the inclusions were trapped.…”

“…The release of CO 2 into the atmosphere also affects long-term global climate and may provide a positive feedback mechanism to volcanism (Huybers and Langmuir, 2009) that may also influence the response of mid-ocean ridge magmatism to glaciation (Maclennan, 2002) and possibly sea-level changes (Burley and Katz, 2015;Tolstoy, 2015). However, the solubility of carbon in silicate melt decreases strongly with decreasing pressure (Dixon et al, 1995), and so most magmas arrive at Earth's surface having lost most of their carbon via degassing. To circumvent the effects of the degassing process, in this study we examine silicate melt inclusions, which are tiny samples of quenched magma (typically <200 µm diameter) trapped in crystals that grow in the magma prior to eruption.…”

Vapor‐Deposited Minerals Contributed to the Martian Surface During Magmatic Degassing

“…Table 1 gives the electron microprobe analyses of the synthetic glass. Micro-Fourier transform infrared analysis of water content using the techniques of Dixon et al (1995) and Mandeville et al (2002) indicates that the source glasses additionally contained 0.4+0.2 wt% water; this uncertainty reflects the combination of the uncertainty induced by thickness variation of individual glass wafers and the overall variability of different aliquots of glass.…”

Deep Carbon Cycling Over the Past 200 Million Years: A Review of Fluxes in Different Tectonic Settings

“…The low solubility of carbon in mid-ocean ridge basalts (e.g., Dixon et al, 1995) means that few samples collected at the surface are undegassed. Carbon flux estimates for MOR are therefore obtained through the measurement of ratios of CO 2 in basaltic glass relative to lithophile trace elements that partition in a similar manner during melting and crystallization, such as Ba, Nb, and Rb, as this allows for the correction of degassed samples 2017are used, where L1 uses continent-scale rifts in concordance with rifts from the geological record, while L2 offers an alternate model using geologically inferred rifts alone.…”