Dehydration of subducting slow-spread oceanic lithosphere in the Lesser Antilles

Paulatto, M.; Laigle, Mireille; Galvé, A.; Charvis, Philippe; Sapin, M.; Bayrakci, Gaye; Evain, Mikaël; Kopp, Heidrun

doi:10.1038/ncomms15980

Cited by 64 publications

(74 citation statements)

References 69 publications

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“…See Section 5.3 for references. Paulatto et al, 2017;Saffer and Wallace, 2015), at least in areas illuminated by earthquakes/signals (i.e.,trench geometries commonly restrict instrumentation and coverage of the 10-30 km depth range, or 'white zone'). It is nevertheless beyond the scope of this contribution to review the huge progress made over the past twenty years on subduction-zone seismicity, moving from Wadati-Benioff to double (or triple) seismic planes, from regular earthquakes (EQ) to slower ones (Ide et al, 2007;Schwartz and Rokosky, 2007), or on source mechanisms or stress drop estimates (e.g., Gao and Wang, 2017).…”

Section: Plate Interface Geometry Across Depthsmentioning

confidence: 99%

“…These burial depths can be compared with the seismicity of two active subduction zones for which earthquakes were relocated with a precision of a couple of km (Alaska: by double-difference, courtesy M. Bostock; Lesser Antilles after Paulatto et al, 2017), hence with a comparable or lower uncertainty than the estimates of metamorphic pressure (whereas EQ locations in the ISC catalogue, for example, tend to be larger). The range of depths reached by SBU broadly coincides with the envelope of intermediate-depth seismicity.…”

Section: Characteristic Trends In Pressure Temperature T/p Gradientmentioning

confidence: 99%

“…High-resolution geophysical imaging recently revealed the existence of several high-Vp patches along the plate interface, advocating for a strong upper plate and/or a relatively dry subduction channel and a locked and potentially loaded megathrust fault (Paulatto et al, 2017; stars on Fig. 8d).…”

Section: Stability Of Mechanical Coupling Through Timementioning

confidence: 99%

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The subduction plate interface: rock record and mechanical coupling (from long to short timescales)

Agard

Plunder

Angiboust

et al. 2018

Lithos

216

294

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Short-and long-term processes at or close to the subduction plate interface (e.g.,mineral transformations, fluid release, seismicity and more generally deformation) might be more closely related than previously thought. Increasing evidence from the fossil rock record suggests that some episodes of their long geological evolution match or are close to timescales of the seismic cycle. This contribution uses rocks recovered (episodically) from subduction zones, together with insights from thermomechanical modelling, to provide a new dynamic vision of the nature, structure and properties of the plate interface and to bridge the gap between the mechanical behavior of active subduction zones (e.g.,coupling inferred from geophysical monitoring) and fossil ones (e.g., coupling required to detach and recover subducted slab fragments). Based on critical observations and an exhaustive compilation of worldwide subducted oceanic units (for which the presence near the plate interface, rock types, pressure, temperature, T/P gradients, thickness and timing of detachment can be assessed), the present study demonstrates how long-term mechanical coupling exerts a key control on detachment from the slab and potential rock recovery. Critical assessment of rock T/P characteristics indicates that these fragments can indeed be used as natural probes and provide reliable information on subduction interface dynamics down to~2.8 GPa. Rock clusters are identified at depths of 30, 55-60 and 80 km, with some differences between rock types. Data also reveal a first-order evolution with subduction cooling (in the first~5 Myr), which is interpreted as reflecting a systematic trend from strong to weak mechanical coupling, after which subduction is lubricated and mostly inhibits rock recovery. This contribution places bounds on the plate interface constitution, regular thickness (b300 m; i.e. where/when there is no detachment), changing geometry and effective viscosity. The concept of 'coupled thickness' is used here to capture subduction interface dynamics, notably during episodes of strong mechanical coupling, and to link long-and short-term deformation. Mechanical coupling depends on mantle wedge rheology, viscosity contrasts and initial structures (e.g.,heterogeneous lithosphere, existence of décollement horizons, extent of hydration, asperities) but also on boundary conditions (convergence rates, kinematics), and therefore differs for warm and cold subduction settings. Although most present-day subduction zone segments (both along strike and downdip) are likely below the detachment threshold, we propose that the most favorable location for detachment corresponds to the spatial transition between coupled and decoupled areas. Effective strain localization involves dissolution-precipitation and dislocation creep but also possibly brittle fractures and earthquakes, even at intermediate depths.

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Section: Plate Interface Geometry Across Depthsmentioning

confidence: 99%

Section: Characteristic Trends In Pressure Temperature T/p Gradientmentioning

confidence: 99%

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The subduction plate interface: rock record and mechanical coupling (from long to short timescales)

Agard

Plunder

Angiboust

et al. 2018

Lithos

216

294

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“…It is commonly proposed that hydration of slab lithospheric mantle takes place in fast-spreading oceans at the outer rise near the trench (Ranero et al, 2003); subsequent dehydration leads to slab embrittlement, which has been invoked for interpreting subduction zone seismicity (Kerrick, 2002;Peacock, 2001;Paulatto et al, 2017;Seno and Yamanaka, 1996). Observational seismic studies infer the extent of serpentinization to be 5-31% (Garth and Rietbrock, 2014;Garth and Rietbrock, 2017;Grevemeyer et al, 2007), which corresponds to H 2 O content of 0.6-3.5 wt% for hydrated slab mantle.…”

Section: Effect Of Serpentinizationmentioning

confidence: 99%

Devolatilization of Subducting Slabs, Part II: Volatile Fluxes and Storage

Tian

Katz

Jones

et al. 2019

Geochem Geophys Geosyst

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Subduction is a crucial part of the long-term water and carbon cycling between Earth's exosphere and interior. However, there is broad disagreement over how much water and carbon is liberated from subducting slabs to the mantle wedge and transported to island-arc volcanoes. In the Tian et al. (2019) Part I, we parameterize the metamorphic reactions involving H 2 O and CO 2 for representative subducting lithologies. On this basis, a two-dimensional reactive transport model is constructed in this Part II. We assess the various controlling factors of CO 2 and H 2 O release from subducting slabs. Model results show that up-slab fluid flow directions produce a flux peak of CO 2 and H 2 O at subarc depths. Moreover, infiltration of H 2 O-rich fluids sourced from hydrated slab mantle enhances decarbonation or carbonation at lithological interfaces, increases slab surface fluxes, and redistributes CO 2 from basalt and gabbro layers to the overlying sedimentary layer. As a result, removal of the cap sediments (by diapirism or off-scraping) leads to elevated slab surface CO 2 and H 2 O fluxes. The modeled subduction efficiency (the percentage of initially subducted volatiles retained until ∼200 km deep) of H 2 O and CO 2 is increased by open-system effects due to fractionation within the interior of lithological layers.

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“…This is in part due to a lack of seafloor instrumentation. Constraints on the physical state of oceanic lithosphere come primarily from 2-D reflection/refraction profiles (e.g., Canales et al, 2017;Fujie et al, 2018;Han et al, 2016Han et al, , 2018Horning et al, 2016;Lizarralde et al, 2004;Ranero et al, 2003;Shillington et al, 2015;Van Avendonk et al, 2011) and a small number of 3-D seismic deployments over geographically limited areas (e.g., Cai et al, 2018;Dunn et al, 2005;Paulatto et al, 2017;Toomey et al, 2007;VanderBeek et al, 2016). Results from these studies suggest that the hydration state of the oceanic plate prior to subduction is highly heterogeneous and is shaped by its tectonic history.…”

Section: Introductionmentioning

confidence: 99%

Pn Tomography of the Juan de Fuca and Gorda Plates: Implications for Mantle Deformation and Hydration in the Oceanic Lithosphere

VanderBeek

Toomey

2019

JGR Solid Earth

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Tomographic analysis of Pn arrivals—the guided P wave propagating within the lithospheric mantle—is ideal for studying uppermost mantle structure. While plate‐scale seismic images of Pn velocities are common beneath the continents, similar scale studies have not been possible within ocean basins due to the sparse distribution of seismic stations. The Cascadia Initiative (CI) data set provides the first opportunity to image spatial variations in lithospheric structure from accretion to subduction across an entire oceanic plate. We invert Pn travel times from local earthquakes for 3‐D variations in isotropic and anisotropic P wave velocity and event hypocentral parameters. Despite surficial evidence of extensive faulting, we find that the velocity structure of the Gorda uppermost mantle is remarkably consistent with predictions from a conductive cooling model. Limited brittle deformation at mantle depths is supported by seismic anisotropy measurements, which show the fast direction of P wave propagation rotates in concert with the magnetic anomaly lineations. This rotation may be explained by local plate kinematics without internal deformation and hydration of the shallow mantle. In contrast to Gorda, the seismic velocity structure of the Juan de Fuca (JdF) plate does not exhibit a clear age dependence. Anomalously slow mantle velocities are found along the southern edge of the JdF plate and are spatially associated with the termini of pseudofaults. We attribute these velocity reductions to mantle alteration by seawater. Our results highlight the heterogeneous nature of the oceanic mantle lithosphere and show that patterns of mantle alteration are not readily discerned from surficial indicators of seafloor deformation.

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Dehydration of subducting slow-spread oceanic lithosphere in the Lesser Antilles

Cited by 64 publications

References 69 publications

The subduction plate interface: rock record and mechanical coupling (from long to short timescales)

The subduction plate interface: rock record and mechanical coupling (from long to short timescales)

Devolatilization of Subducting Slabs, Part II: Volatile Fluxes and Storage

Pn Tomography of the Juan de Fuca and Gorda Plates: Implications for Mantle Deformation and Hydration in the Oceanic Lithosphere

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