Geochemical characterization of two distinctive systems with evidence of chemosynthetic activity, explored at the SE Pacific margin off Chile (46°S and 33°S)

Muñoz, Práxedes; Cárdenas, Lissette; Garbe‐Schönberg, Dieter; Sellanes, Javier; Dezileau, Laurent; Melville, Ives; Mendes, Stephanie D.

doi:10.1016/j.pocean.2016.09.002

Cited by 2 publications

(1 citation statement)

References 83 publications

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“…Gas seepage on the south Chilean Margin was first reported by Sellanes et al [2004] in what is now called the Concepción Methane Seepage Area (CMSA), with more recent evidence for active and paleo seepage [Klaucke et al, 2012]. Seepage of methane-rich fluids typically cluster near these faults and support robust chemosynthetic communities near the seafloor [Munoz et al, 2016;Sellanes et al, 2008]. It has been suggested that onset of seepage in this region may be linked to the tectonic history of the margin, potentially as recent as the 2010 Maule earthquake in some sectors of the margin [Geersen et al, 2016;Villar-Muñoz et al, 2021].…”

Section: Geologic and Tectonic Settingmentioning

confidence: 99%

Links between spatially heterogeneous pore water geochemistry, fluid migration, and methane hydrate near a seafloor mound venting structure on the south Chilean Margin (41°S)

Clementi

Rosenthal

Bova

et al. 2022

Preprint

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Pore water freshening (i.e., decreases in dissolved Cl) has been documented in marine sediments along most active margins, with the migration of deep fluids or methane hydrate dissociation often invoked as sources of freshening in the sediment column. During D/V JOIDES Resolution Expedition 379T in 2019, two new sites (J1005 and J1006) were cored near ODP Site 1233 (41°S), adjacent to a seafloor mound venting structure. The three sites are less than 10 km apart but show marked differences in pore water chemistry and methane hydrate occurrence. The extent of Cl decrease is a function of distance from the mound, with the strongest freshening occurring at the closest site (J1006), which is the only site where methane hydrate was observed.Methane fluxes follow the same pattern, suggesting a common control. Increasing oxygen and decreasing hydrogen isotopes point to deep mineral bound water as the primary source of freshening near the mound, with fluids originating ˜2.5 km below seafloor near the décollement. Secondary influences from methane hydrate dissociation and ash diagenesis also appear to influence regional pore water chemistry. The variability in pore water freshening suggests that fluid migration and eventual expulsion at the venting structure follows narrow pathways, likely along faults within the forearc complex. The migration of deep, gascharged fluids may also support methane hydrate saturations greater than in situ organic carbon diagenesis would allow, but nonetheless consistent with geophysical estimates. Together, the data highlight an important link between fluid migration and methane hydrate formation on the Chilean Margin.

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Section: Geologic and Tectonic Settingmentioning

confidence: 99%

Links between spatially heterogeneous pore water geochemistry, fluid migration, and methane hydrate near a seafloor mound venting structure on the south Chilean Margin (41°S)

Clementi

Rosenthal

Bova

et al. 2022

Preprint

View full text Add to dashboard Cite

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The role of marine sediment diagenesis in the modern oceanic magnesium cycle

2019

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The oceanic magnesium cycle is largely controlled by continental weathering and marine authigenic mineral formation, which are intimately linked to long-term climate. Uncertainties in the magnesium cycle propagate into other chemical budgets, and into interpretations of paleo-oceanographic reconstructions of seawater δ26Mg and Mg/Ca ratios. Here, we produce a detailed global map of the flux of dissolved magnesium from the ocean into deeper marine sediments (greater than ∼1 meter below seafloor), and quantify the global flux and associated isotopic fractionation. We find that this flux accounts for 15–20% of the output of magnesium from the ocean, with a flux-weighted fractionation factor of ∼0.9994 acting to increase the magnesium isotopic ratio in the ocean. Our analysis provides the best constraints to date on the sources and sinks that define the oceanic magnesium cycle, including new constraints on the output flux of magnesium and isotopic fractionation during low-temperature ridge flank hydrothermal circulation.

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Geochemical characterization of two distinctive systems with evidence of chemosynthetic activity, explored at the SE Pacific margin off Chile (46°S and 33°S)

Cited by 2 publications

References 83 publications

Links between spatially heterogeneous pore water geochemistry, fluid migration, and methane hydrate near a seafloor mound venting structure on the south Chilean Margin (41°S)

Links between spatially heterogeneous pore water geochemistry, fluid migration, and methane hydrate near a seafloor mound venting structure on the south Chilean Margin (41°S)

The role of marine sediment diagenesis in the modern oceanic magnesium cycle

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