A Vent-Field-Scale Model of the East Pacific Rise 9°50'N Magma-Hydrothermal System

Lowell, R. P.; Farough, A.; Germanovich, L. N.; Hebert, L. B.; Horne, R. C.

doi:10.5670/oceanog.2012.13

Cited by 15 publications

(25 citation statements)

References 10 publications

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“…Note that the results here are slightly different from those shown in Lowell et al . [] and Bemis et al . [] because of slightly different averaging.…”

Section: Resultsmentioning

confidence: 99%

“…In the two‐limb single‐pass model, we assume that as the ascending, sulfate‐depleted, hot hydrothermal fluid mixes with the sulfate‐rich, shallow recharge of cold seawater in the extrusive layer, anhydrite and other minerals precipitate, resulting in permeable channels of focused flow separated from regions of low‐temperature diffuse flow [ Lowell et al ., , ; Germanovich et al ., ]. We also assume that there is no conductive cooling of the high‐temperature fluid or mixing with seawater during its ascent.…”

Section: Single‐pass Modeling Of Seafloor Hydrothermal Systemsmentioning

confidence: 99%

“…Lowell [] and Lowell et al . [] applied the method to a number of hydrothermal systems at slow‐spreading ridges and at 9°50′N on the East Pacific Rise (EPR), respectively.…”

Section: Introductionmentioning

confidence: 99%

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Characteristics of magma‐driven hydrothermal systems at oceanic spreading centers

Lowell

Farough

Hoover

et al. 2013

Geochem Geophys Geosyst

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104

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[1] We use one-and two-limb single-pass models to de termine vent field characteristics such as mass flow rate Q, bulk permeability in the discharge zone k d , thickness of the conductive boundary layer at the base of the system d, magma replenishment rate, and residence time in the discharge zone. Data on vent temperature, vent field area, heat output, and the surface area and depth of the subaxial magma chamber (AMC) constrain the models. The results give Q~100 kg/s, k d~1 0 À13 m 2 , and d~10 m, essentially independent of spreading rate, and detailed characteristics of the AMC. In addition, we find no correlation between heat output at individual vent fields and spreading rate or depth to the AMC. We conclude that high-temperature hydrothermal systems are driven by local magma supply rates in excess of that needed for steady state crustal production and that crustal permeability enables hydrothermal circulation to tap magmatic heat regardless of AMC depth. Using data on partitioning of heat flow between focused and diffuse flow, we find that 80-90% of the hydrothermal heat output is derived from high-temperature fluid, even though much of the heat output discharges as low-temperature fluid. In some cases, diffuse flow fluids may exhibit considerable conductive cooling or heating. By assuming conservative mixing of diffuse flow fluids at East Pacific Rise 9 50 0 N, we find that most transport of metals such as Fe and Mn occurs in diffuse flow and that CO 2 , H 2 , and CH 4 are taken up by microbial activity.

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“…Note that the results here are slightly different from those shown in Lowell et al . [] and Bemis et al . [] because of slightly different averaging.…”

Section: Resultsmentioning

confidence: 99%

Section: Single‐pass Modeling Of Seafloor Hydrothermal Systemsmentioning

confidence: 99%

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Characteristics of magma‐driven hydrothermal systems at oceanic spreading centers

Lowell

Farough

Hoover

et al. 2013

Geochem Geophys Geosyst

Self Cite

104

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“…With a total low-temperature fluid flux of the vent field at 9 o 50'N East Pacific Rise of 1170 kg s -1 (Lowell et al, 2012), we estimate a total vent field productivity of 3.8 × 10 6 9.3 × 10 6 g C y -1 . If this biomass remained in the vent field (10 3 -10 4 m 2 (Lowell et al, 2012)), it would represent a very high concentration of labile carbon for the deep sea (3.8 × 10 2 to 9.3 × 10 3 g C m -2 y -1 ).…”

Section: 4mentioning

confidence: 96%

Productivity, metabolism and physiology of free-living chemoautotrophic Epsilonproteobacteria

McNichol¹

2016

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Chemoautotrophic ecosystems at deep-sea hydrothermal vents were discovered in 1977, but not until 1995 were free-living autotrophic Epsilonproteobacteria identified as important microbial community members. Because the deep-sea is food-starved, the autotrophic metabolism of hydrothermal vent Epsilonproteobacteria may be very important for deep-sea consumers. However, quantifying their metabolic activities in situ has remained difficult, and biochemical mechanisms underlying their autotrophic physiology are poorly described. To gain insight into environmental processes, an approach was developed for incubations of microbes at in situ pressure and temperature (25 MPa, 24 o C) with various combinations of electron donors/acceptors (H 2 , O 2 and NO 3 -and 13 HCO 3 -) as a tracer to track carbon fixation. During short (18-24 h) incubations of low-temperature vent fluids from Crab Spa (9 o N East Pacific Rise), the concentration of electron donors/acceptors and cell numbers were monitored to quantify microbial processes. Measured rates were generally higher than previous studies, and the stoichiometry of microbially-catalyzed redox reactions revealed new insights into sulfur and nitrogen cycling. Single-cell, taxonomically-resolved tracer incorporation showed Epsilonproteobacteria dominated carbon fixation, and their growth efficiency was calculated based on electron acceptor consumption. Using these data, in situ primary productivity, microbial standing stock, and average biomass residence time of the deep-sea vent subseafloor biosphere were estimated. Finally, the population structures of the most abundant genera Sulfurimonas and Thioreductor were shown to be strongly influenced by pO 2 and temperature respectively, providing a mechanism for niche differentiation in situ. To gain insights into the core biochemical reactions underlying autotrophy in Epsilonprotebacteria, a theoretical metabolic model of Sulfurimonas denitrificans was developed. Validated iteratively by comparing in silico yields with data from chemostat experiments, the model generated hypotheses explaining critical, yet so far unresolved reactions supporting chemoautotrophy in Epsilonproteobacteria. For example, it provides insight into how energy is conserved during sulfur oxidation coupled to denitrification, how reverse electron transport produces ferredoxin for carbon fixation, and why aerobic growth yields are only slightly higher compared to denitrification. As a whole, this thesis provides important contributions towards understanding core mechanisms of chemoautrophy, as well as the in situ productivity, physiology and ecology of autotrophic Epsilonproteobacteria.

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“…The EPR is a fast spreading mid-ocean ridge (Sinton and Detrick, 1992) with a relatively high inferred rate of magmatic resupply (Fornari et al, 2012;Liu and Lowell, 2009;Lowell et al, 2012), giving rise to vigorous hydrothermal venting at several spots along the ridge (Von Damm et al, 2003Damm et al, , 1997Von Damm, 2000). It is one of the best-studied mid-ocean ridge systems and copious time series datasets of chemistry, biology, and seismology exist (Tolstoy et al, 2006;Von Damm and Lilley, 2004;Shank et al, 1998).…”

Section: Study Site: Biogeotransect (9 • • • N) East Pacific Risementioning

confidence: 98%

Subsurface conditions in hydrothermal vents inferred from diffuse flow composition, and models of reaction and transport

Larson

Houghton²,

Lowell

et al. 2015

Earth and Planetary Science Letters

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Keywords: hydrothermal free energy modeling anhydrite subsurface diffuse flow Chemical gradients in the subsurface of mid-ocean ridge hydrothermal systems create an environment where minerals precipitate and dissolve and where chemosynthetic organisms thrive. However, owing to the lack of easy access to the subsurface, robust knowledge of the nature and extent of chemical transformations remains elusive. Here, we combine measurements of vent fluid chemistry with geochemical and transport modeling to give new insights into the under-sampled subsurface. Temperature-composition relationships from a geochemical mixing model are superimposed on the subsurface temperature distribution determined using a heat flow model to estimate the spatial distribution of fluid composition. We then estimate the distribution of Gibb's free energies of reaction beneath mid oceanic ridges and by combining flow simulations with speciation calculations estimate anhydrite deposition rates. Applied to vent endmembers observed at the fast spreading ridge at the East Pacific Rise, our results suggest that sealing times due to anhydrite formation are longer than the typical time between tectonic and magmatic events. The chemical composition of the neighboring low temperature flow indicates relatively uniform energetically favorable conditions for commonly inferred microbial processes such as methanogenesis, sulfate reduction and numerous oxidation reactions, suggesting that factors other than energy availability may control subsurface microbial biomass distribution. Thus, these model simulations complement fluid-sample datasets from surface venting and help infer the chemical distribution and transformations in subsurface flow.

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A Vent-Field-Scale Model of the East Pacific Rise 9°50'N Magma-Hydrothermal System

Abstract: A vent-field-scale model of the East Pacific Rise 9°50'N magma-hydrothermal system.

Cited by 15 publications

References 10 publications

Characteristics of magma‐driven hydrothermal systems at oceanic spreading centers

Characteristics of magma‐driven hydrothermal systems at oceanic spreading centers

Productivity, metabolism and physiology of free-living chemoautotrophic Epsilonproteobacteria

Subsurface conditions in hydrothermal vents inferred from diffuse flow composition, and models of reaction and transport

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