Widespread fluid expulsion along the seafloor of the Costa Rica convergent margin

Bohrmann, Gerhard; Heeschen, Katja; Jung, C.; Weinrebe, Willi; Baranov, Boris; Cailleau, B.; Heath, Richard J.; Hühnerbach, Veit; Hort, Matthias; Masson, Douglas G.; Trummer, Irmgard

doi:10.1046/j.1365-3121.2002.00400.x

Cited by 97 publications

(96 citation statements)

References 40 publications

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Section: Volatiles and Fluidsmentioning

confidence: 99%

“…Along the entire Costa Rica margin, active fluid venting is indicated by elevated methane concentrations in the bottom water McAdoo et al, 1996;Bohrmann et al, 2002;Sahling et al, 2008). Chemoautotrophic and methanotrophic communities mark cold vents at numerous localities, but higher community abundances have been found where subducted seamounts have triggered fractures, slides, and slumps that break a low-permeability, shallow sediment carapace, allowing ascending fluids to feed the communities.…”

Section: Volatiles and Fluidsmentioning

confidence: 99%

“…Widespread mounds, some tens of meters high and a few hundred meters wide, have been monitored with current meters and hydrographic stations (Flüh et al, 2004). Outcropping carbonates on top and at the flanks indicate that these mounds are formed by authigenic precipitation at sites with abundant signs of fluid flow (Bohrmann et al, 2002;Hensen et al, 2004).…”

Section: Site Survey Datamentioning

confidence: 99%

“…Chemoautotrophic and methanotrophic communities mark cold vents at numerous localities, but higher community abundances have been found where subducted seamounts have triggered fractures, slides, and slumps that break a low-permeability, shallow sediment carapace, allowing ascending fluids to feed the communities. These communities are particularly concentrated along headwall scarps Bohrmann et al, 2002;. Mud volcanoes and mud diapirs have also been found, particularly across the middle slope, and are associated with a high density of chemosynthetic vents.…”

mentioning

confidence: 99%

“…Mud volcanoes and mud diapirs have also been found, particularly across the middle slope, and are associated with a high density of chemosynthetic vents. The chemistry of the pore fluids sampled at these midslope features is indicative of clay dehydration reactions at depth (Shipley et al, 1992;Bohrmann et al, 2002;Grevemeyer et al, 2004;Hensen et al, 2004;Sahling et al, 2008).Along the décollement and the upper prism fault zone, coring and sampling during Ocean Drilling Program (ODP) Legs 170 and 205 offshore the Nicoya Peninsula revealed freshened pore waters containing elevated Ca, Li, and C 3 -C 6 hydrocarbon concentrations and low K concentrations (Kimura, Silver, Blum, et al, 1997;Silver et al, 2000;Chan and Kastner, 2000;Morris, Villinger, Klaus, et al, 2003;Kastner et al, 2006). These fluids contrast with pore fluids from below the décollement and between the décollement and upper fault zone that have near-seawater chemistry (Kimura, Silver, Blum, et al, 1997;Morris, Villinger, Klaus, et al, 2003).…”

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confidence: 99%

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Expedition 344 summary

Li¹,

Malinverno²,

Torres³

et al. 2013

Proceedings of the IODP

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Expedition 344 summaryProc. IODP | Volume 344 2 from velocity-strengthening to velocity-weakening friction, and shear becomes localized. The onset of seismogenic behavior is correlated with the intersection of the 100°-150°C isotherm and the subduction thrust (Hyndman et al., 1997;Oleskevich et al., 1999). With increasing depth down the subduction thrust, the frictional characteristics undergo a second transition either due to the juxtaposition with the forearc mantle or because the rocks are heated to 350°-450°C and can no longer store elastic stresses needed for rupture. Transitional regions between the three zones have conditional stability and can host rupture but are generally not thought to be regions where large earthquakes initiate.Although this three-zone two-dimensional view of the subduction thrust provides a reasonable framework, it is simplistic. Rupture models for large subduction earthquakes suggest significant fault plane heterogeneity in slip and moment release that in three dimensions is characterized as patchiness (Bilek and Lay, 2002). Additionally, we now know the transition zone from stable to unstable sliding is not simple but hosts a range of fault behaviors that includes creep events, strain transients, slow and silent earthquakes, and low-frequency earthquakes (Peng and Gomberg, 2010;Beroza and Ide, 2011;Ide, 2012).Fundamentally unknown are the processes that change fault behavior from stable sliding to stick-slip behavior. Understanding these processes is important for understanding earthquakes, the mechanics of slip, and rupture dynamics. For a fault to undergo unstable slip, fault rocks must have the ability to store elastic strain, be velocity weakening, and have sufficient stiffness. Hypotheses for mechanisms leading to the transition between stable and unstable slip invoke temperature, pressure, and strain-activated processes that lead to downdip changes in the mechanical properties of rocks. These transitions are also sensitive to fault zone composition, lithology, fabric, and fluid pressures.The composition of the material in the fault zone and its contrast with the surrounding wall rock play a key role in rock frictional behavior. The frictional state of the incoming sediment changes progressively with increasing temperature and pressure as it travels downdip. Important lithologic factors influencing friction are composition, fabric, texture, and cementation of rocks, as well as fluid pore pressure (Bernabé et al., 1992;Moore and Saffer, 2001;Beeler, 2007;Marone and Saffer, 2007;Collettini et al., 2009). For example, fault rocks with high phyllosilicate content are generally weaker than rocks with low phyllosilicate content (Ikari et al., 2011). Sediment properties including porosity, permeability, consolidation state, and alteration history also exert a strong influence on fault zone behavior. At erosive margins, where the plate boundary cuts into the overriding plate, the composition and strength of the upper plate is also important (McCaffrey, 1993).Field observations and la...

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Section: Volatiles and Fluidsmentioning

confidence: 99%

Section: Volatiles and Fluidsmentioning

confidence: 99%

Section: Site Survey Datamentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Expedition 344 summary

Li¹,

Malinverno²,

Torres³

et al. 2013

Proceedings of the IODP

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Hydrocarbon seepage and its sources at mud volcanoes of the Kumano forearc basin, Nankai Trough subduction zone

Pape

Geprägs

Hammerschmidt

et al. 2014

Geochem Geophys Geosyst

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Twelve submarine mud volcanoes (MV) in the Kumano forearc basin within the Nankai Trough subduction zone were investigated for hydrocarbon origins and fluid dynamics. Gas hydrates diagnostic for methane concentrations exceeding solubilities were recovered from MVs 2, 4, 5, and 10. Molecular ratios (C 1 /C 2 < 250) and stable carbon isotopic compositions (d 13 C-CH 4 >240& V-PDB) indicate that hydratebound hydrocarbons (HCs) at MVs 2, 4, and 10 are derived from thermal cracking of organic matter. Considering thermal gradients at the nearby IODP Sites C0009 and C0002, the likely formation depth of such HCs ranges between 2300 and 4300 m below seafloor (mbsf). With respect to basin sediment thickness and the minimum distance to the top of the plate boundary thrust we propose that the majority of HCs fueling the MVs is derived from sediments of the Cretaceous to Tertiary Shimanto belt below Pliocene/Pleistocene to recent basin sediments. Considering their sizes and appearances hydrates are suggested to be relicts of higher MV activity in the past, although the sporadic presence of vesicomyid clams at MV 2 showed that fluid migration is sufficient to nourish chemosynthesis-based organisms in places. Distributions of dissolved methane at MVs 3, 4, 5, and 8 pointed at fluid supply through one or few MV conduits and effective methane oxidation in the immediate subsurface. The aged nature of the hydrates suggests that the major portion of methane immediately below the top of the methane-containing sediment interval is fueled by current hydrate dissolution rather than active migration from greater depth.

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High density of structurally controlled, shallow to deep water fluid seep indicators imaged offshore Costa Rica

Kluesner

Silver

Bangs

et al. 2013

Geochem Geophys Geosyst

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[1] We used high-resolution mapping to document 161 sites of potential fluid seepage on the shelf and slope regions where no geophysical seep indicators had been reported. Identified potential seabed seepage sites show both high-backscatter anomalies and bathymetric expressions, such as pockmarks, mounds, and ridges. Almost all identified seabed features are associated with bright spots and flat spots beneath, as mapped within the 3-D seismic grid. We obtained EM122 multi-beam data using closely spaced receiver beams and 4-5 times overlapping multi-beam swaths, which greatly improved the sounding density and geologic resolvability of the data. At least one location shows an acoustic plume in the water column on a 3.5 kHz profile, and this plume is located along a fault trace and above surface and subsurface seepage indicators. Fluid indicators are largely associated with folds and faults within the sediment section, and many of the faults continue into and offset the reflective basement. A dense pattern of normal faults is seen on the outer shelf in the multi-beam bathymetry, backscatter, and 3-D seismic data, and the majority of fluid seepage indicators lie along mapped fault traces. Furthermore, linear mounds, ridges, and pockmark chains are found on the upper, middle, and lower slope regions. The arcuate shape of the shelf edge, projection of the Quepos Ridge, and high density of potential seep sites suggest that this area may be a zone of former seamount/ridge subduction. These results demonstrate a much greater potential seep density and distribution than previously reported across the Costa Rican margin.Components: 12,500 words, 15 figures.Keywords: fluid seepage; fluid flow; subduction zones; Marine Geology and Geophysics; Costa Rica.Index Terms: 3060 Marine Geology and Geophysics: Subduction zone processes (1031, 3613, 8170, 8413)

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Widespread fluid expulsion along the seafloor of the Costa Rica convergent margin

Cited by 97 publications

References 40 publications

Expedition 344 summary

Expedition 344 summary

Hydrocarbon seepage and its sources at mud volcanoes of the Kumano forearc basin, Nankai Trough subduction zone

High density of structurally controlled, shallow to deep water fluid seep indicators imaged offshore Costa Rica

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