Geophysical Constraints on the Volume of Hydrothermal Flow at Ridge Axes

Sleep, Norman H.; Morton, Janet L.; Burns, L.E.; Wolery, Thomas J.

doi:10.1007/978-1-4899-0402-7_4

Cited by 14 publications

(5 citation statements)

References 26 publications

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“…Chemical analysis of hydrothermal fluids venting along ridges provided constraints for estimation of the relative importance of these vents and lower-temperature off-axis vents (which have still not been adequately observed or sampled). Chemical fluxes were computed assuming that the bulk of the hydrothermal flow vents at the axis [e.g., Edmond et al, 1979;Von Datum et al, 1985] or assuming significant contributions of off-axis vents [Thompson, 1983;Mottl, 1983;Sleep et al, 1983]. As the latter estimates were based at least in part on thermal reasoning similar to this paper, it is useful to examine estimates that were obtained mainly from considering the chemistry itself.…”

Section: Resultsmentioning

confidence: 99%

A Mid‐Ocean Ridge Thermal Model: Constraints on the volume of axial hydrothermal heat flux

Morton¹,

Sleep²

1985

J. Geophys. Res.

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211

107

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The depth to the axial magma chamber at three oceanic spreading centers, as indicated by seismic reflection surveys, is greater than that predicted by conductive cooling thermal models of ridge crests. The additional cooling at the ridge axis is owed to the circulation of seawater through the shallow crust. A theoretical model for the temperature distribution at spreading centers, which includes distributed heat sources and sinks, is presented. By representing the hydrothermal heat loss as a series of heat sinks, the depths to the axial magma chamber at the East Pacific Rise at latitude 9øN., the southern Juan de Fuca Ridge, and the Lau Basin spreading center are modeled. Heat sinks are added to the input model to increase the solidus depth until the computed magma chamber depth matches the magma chamber depth determined by seismic reflection surveys. The thermal modeling indicates that the axial hydrothermal heat flux is between 7.1 x 10 6 and 13.8 x 10 6 MJ/m 2, or 10 to 20% of the total missing heat at the ridge axis, requiring extensive low-temperature circulation off axis. High-temperature vents that are spaced 1 km apart and are active between 4 and 10% of the time would account for the axial hydrothermal heat loss.

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Section: Resultsmentioning

confidence: 99%

A Mid‐Ocean Ridge Thermal Model: Constraints on the volume of axial hydrothermal heat flux

Morton¹,

Sleep²

1985

J. Geophys. Res.

Self Cite

211

107

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“…The decline in observable fluid flux and maximum measured vent fluid temperature from 51 • C on 1 August 1993, to 36 • C in mid-October, to only 9 • C in July 1994 shows that the heat source at the Flow site was nearly exhausted within a year. Using the volume of extruded lava (5.4 × 10 6 m 3 ) estimated by Chadwick et al (1995) and the basalt properties found in Sleep et al (1983), we calculate that the heat available in the lava mound through latent heat of crystallization and cooling Figure 8. Geologic interpretation of CoAxial hydrothermal evolution, with depth below sea level in meters on vertical axis and latitude ( • N) on horizontal axis.…”

Section: Discussionmentioning

confidence: 99%

Seafloor eruptions and evolution of hydrothermal fluid chemistry

Butterfield

Jonasson

Massoth

et al. 1997

Philosophical Transactions of the Royal Society of London. Seri

230

100

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A major challenge confronting geochemists is to relate the chemistry of vented hydrothermal fluids to the local or regional tectonic and volcanic state of mid-ocean ridges. After more than 15 years of sampling submarine hydrothermal fluids, a complex picture of spatial and temporal variability in temperature and composition is emerging. Recent time-series observations and sampling of ridge segments with confirmed recent volcanic eruptions (CoAxial and North Cleft on the Juan de Fuca ridge and 9-10 • N on the East Pacific Rise) have created a first-order understanding of how hydrothermal systems respond to volcanic events on the seafloor. Phase separation and enhanced volatile fluxes are associated with volcanic eruptions, with vapour-dominated fluids predominating in the initial post-eruption period, followed in time by brine-dominated fluids, consistent with temporary storage of brine below the seafloor. Chemical data for CoAxial vents presented here are consistent with this evolution. Rapid changes in output and composition of hydrothermal fluids following volcanic events may have a profound effect on microbiological production, macrofaunal colonization, and hydrothermal heat and mass fluxes. Size and location of the heat source are critical in determining how fast heat is removed and whether subseafloor microbial production will flourish. CoAxial event plumes may be a direct result of dyking and eruption of lavas on the seafloor.

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“…Modelling of these pro ces ses is mostly based on the assumption that hydrothermal exchange is proportional to spreading rate (e.g., Berner et al 1983, Sleep et al 1983, while measurements on the East Pacific ridge suggest rather a correlation with tectonic reorganizations . Exchanges of chemical elements between basalt and water during hydrothermal cooling contribute to both the control of sea-water composition and to the formation of metalliferous deposits.…”

Section: Low-temperature Alterationmentioning

confidence: 99%