Influence of kinetics on the smectite to illite transition in the Barbados accretionary prism

Bekins, Barbara A.; McCaffrey, Anne M.; Dreiss, Shirley J.

doi:10.1029/94jb01187

Cited by 62 publications

(89 citation statements)

References 23 publications

(3 reference statements)

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“…Because of this, compared to quartz-rich silty or sandy sediments, clays dewater more slowly under compression and are prone to developing excess pore pressures. Sediment diagenesis can also lead to excess pore pressures because common reactions such as opal to quartz and smectite dehydration release mineral-bound water (Colten-Bradley, 1987;Fitts and Brown, 1999;Bekins et al, 1994;Kastner et al, 2014).…”

Section: Hydrologic Effectsmentioning

confidence: 99%

Lithologic control of frictional strength variations in subduction zone sediment inputs

et al. 2018

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At convergent margins, marine sediments deposited seaward of the subduction zone forearc on the incoming plate (the "subduction inputs") represent the initial condition for geomechanical processes during subduction. The frictional strength of these sediments is a key parameter governing deformation during subduction, which is controlled to first order by lithologic composition. We combine here the results of laboratory friction experiments and quantification of mineral assemblage for scientific drilling samples recovered from three particularly well-studied subduction zones: the Nankai Trough (southwestern Japan), the Japan Trench (northeastern Japan), and Costa Rica. In the Japan Trench, frictionally weak smectite-rich pelagic clay contrasts sharply with stronger, more siliceous hemipelagic material. This strength contrast dictates the stratigraphic position of initial plate boundary formation and influences slip behavior of the shallow megathrust. In the Costa Rica subduction zone, relatively weak clay-rich hemipelagic sediment overlies frictionally strong pelagic nannofossil oozes and chalks, which could be a factor for the development of features such as a small amount of offscraping near the toe and subduction erosion where ooze or chalk dominates. In the Nankai Trough, however, a wide range of frictional strength values is observed that does not correlate with clay mineral content. In this case, mechanical behavior at Nankai is likely influenced by other factors related to diagenesis or fluid overpressuring.

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Section: Hydrologic Effectsmentioning

confidence: 99%

Lithologic control of frictional strength variations in subduction zone sediment inputs

et al. 2018

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“…[12] To estimate reaction progress, we track sediment from its initial position outboard of the trench through the modeled temperature field as it is underthrust [e.g., Bekins et al, 1994]. This provides a thermal history for the sediment, which we combine with kinetic expressions to calculate reaction progress.…”

Section: Methodsmentioning

confidence: 99%

Along‐strike variations in underthrust sediment dewatering on the Nicoya margin, Costa Rica related to the updip limit of seismicity

Spinelli

2004

Geophysical Research Letters

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Along the Costa Rican subduction zone offshore the Nicoya peninsula, an offset in the updip limit of seismicity coincides with a transition between subduction of warm crust generated at the Cocos‐Nazca Spreading Center and cool crust formed at the East Pacific Rise. We evaluate whether the observed difference in thermal state of incoming crust would result in significant differences in sediment dehydration reaction progress along strike, thought to be a control on the updip limit of seismicity. We combine thermal models with models of dehydration reaction kinetics for opal and smectite to estimate the distribution of diagenetic fluid sources. The modeled distribution of diagenetic fluid sources mimics the pattern of the updip limit of seismicity; seismicity begins ∼15–20 km landward of most of the smectite‐to‐illite transition. This suggests that the location of the updip limit of seismicity may be influenced by the dissipation of fluid overpressures landward of smectite‐to‐illite dehydration.

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“…The source of freshwater was attributed to low-temperature clay dehydration processes (e.g., smectite-to-illite transformation) that typically occur over a temperature range of 60°-160°C (e.g., Bekins et al, 1994). With a temperature gradient of ~60°C/km at Site U1327, the source of this freshwater pool is at a depth of ~1000-2750 mbsf.…”

Section: Inorganic Pore Water Constituents and Upward Fluid Migrationmentioning

confidence: 99%

Expedition 311 Synthesis: scientific findings

Riedel¹,

Collett²,

Malone³

2010

Proceedings of the IODP

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Integrated Ocean Drilling Program Expedition 311 was conducted to study gas hydrate occurrences and their evolution along a transect spanning the entire northern Cascadia accretionary margin. A transect of four research sites (U1325, U1326, U1327, and U1329) was established over a distance of 32 km, extending from Site U1326 near the deformation front to Site U1329 at the eastern limit of the inferred gas hydrate occurrence zone. In addition to the transect, a fifth site (U1328) was established at a cold vent setting with active fluid and gas expulsion, which provided an opportunity to compare regional pervasive fluid-flow regimes to a site of focused fluid advection. In this synthesis, a revised gas hydrate formation model is proposed based on a combination of geophysical, geochemical, and sedimentological data acquired during and after Expedition 311 and from previous studies. The main elements of this revised model are as follows:1. Fluid expulsion by tectonic compression of accreted sediments at nonuniform expulsion rates along the transect results in the evolution of variable pore water regimes across the margin. Sites closer to the deformation front are characterized by pore fluids enriched in dissolved salts at depth, where zeolite formation from ash diagenesis is dominant. In contrast, the landward portion of the margin shows a freshening of pore fluids with depth as a result of the progressive overprinting of diagenetic salt generation with freshwater generation from the smectite-to-illite transition at greater depth. 2. In situ methane produced by microbial CO 2 reduction within the gas hydrate stability zone is the prevalent gas source for gas hydrate formation. 3. Some minor methane advection from depth is required overall to explain the occurrence of gas hydrate (and the associated downhole isotopic signatures of CH 4 and CO 2 ) within the sediments of the accretionary prism and the absence of gas hydrate within the abyssal plain sediments. In contrast, methane migrating from depth is a dominant source for gas hydrate formation at the cold vent Site U1328 (Bullseye vent). 4. Gas hydrate preferentially forms in coarser grained sandy/silt turbidites, resulting in very high local gas hydrate concentrations. Typically, gas hydrate occupies <5% of the pore space throughout the gas hydrate stability zone. Higher gas hydrate saturations were observed in intervals with abundant coarse-

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Influence of kinetics on the smectite to illite transition in the Barbados accretionary prism

Cited by 62 publications

References 23 publications

Lithologic control of frictional strength variations in subduction zone sediment inputs

Lithologic control of frictional strength variations in subduction zone sediment inputs

Along‐strike variations in underthrust sediment dewatering on the Nicoya margin, Costa Rica related to the updip limit of seismicity

Expedition 311 Synthesis: scientific findings

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