Structure of oceanic crust and serpentinization at subduction trenches

Grevemeyer, Ingo; Ranero, César R.; Ivandic, Monika

doi:10.1130/ges01537.1

Cited by 185 publications

(296 citation statements)

References 105 publications

(227 reference statements)

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“…Blue‐shaded area represents the velocity envelope from mature Atlantic‐type oceanic crust (144–170 Ma, White et al, ). Pink‐shaped area corresponds to the velocity envelope of oceanic crust found at slow‐spreading ridges as compiled by Grevemeyer et al (). Green‐shaded area corresponds to the velocity envelope of serpentinized mantle presented by Dean et al ().…”

Section: Discussionmentioning

confidence: 99%

Geology of the Ionian Basin and Margins: A Key to the East Mediterranean Geodynamics

et al. 2019

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We revisit the nature, structure, and evolution of the Ionian Basin and its surrounding passive margins (Apulia, Eastern Sicily/Malta, and Cyrenaica margins). Relying on geological observations (wells, dredges, and dives) and seismic calibrations from the surrounding platforms and escarpments, we present age correlations for the deepest sedimentary sequences of the Ionian Basin. Two‐ship deep refraction seismic data combined with reprocessed reflection seismic data enable us to identify, characterize, and map these thick sedimentary sequences and to present a consistent seismic stratigraphy across the basin. At a larger scale, we present new geological transects illustrating the tectonostratigraphic relationships between the Ionian Basin and its surrounding rifted margins. On this basis, we suggest that a Late Triassic‐Early Jurassic rifting preceded the late Early Jurassic to Middle Jurassic formation of the Ionian Basin. The combination of geophysical and geological arguments suggests that the entire deep basin is floored with oceanic crust of normal thickness, but with high seismic velocity in the upper part. Upscaling our results in the framework of the eastern Mediterranean, we propose that the Ionian Basin represents the remnant of a short‐lived oceanic basin resulting from the interaction between two propagating oceans: the Central Atlantic and the Neo‐Tethys.

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Section: Discussionmentioning

confidence: 99%

Geology of the Ionian Basin and Margins: A Key to the East Mediterranean Geodynamics

et al. 2019

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“…The velocities from 6.8-7.2 km/s to 8.0 km/s are too low for unaltered mantle and may result from serpentinization of the upper mantle (e.g., in fracture zones, Detrick et al, 1993, the COT of nonvolcanic rifted margins, Davy et al, 2016, and slow or ultraslow spreading oceanic basins; e.g., the Labrador Sea; Delescluse et al, 2015;Osler & Louden, 1992 or magma intrusion (e.g., in NW Indian Ocean; Gupta et al, 2010). In our final model (Figure 3b), velocities at depths >3 km below the top basement sit outside the envelopes for Pacific and magmatic oceanic crust newly compiled by Grevemeyer et al (2018;Figure 9a well with the velocity profiles in the models of thin oceanic crust overlying serpentinized mantle in the North Atlantic Ocean (Figure 9b; Davy et al, 2016;Funck et al, 2003;Hopper et al, 2004;Whitmarsh et al, 1996) and the exhumed mantle zone in West Iberia (Figure 9b; Dean et al, 2000;Sallarès et al, 2013) and the Central Tyrrhenian Basin (Figure 9c; Prada et al, 2014). Serpentinization of the upper mantle is facilitated when the crust is thin and fractured to allow seawater to flow in (Minshull et al, 1998;Sauter et al, 2013;Shillington et al, 2006).…”

Section: Reflection Moho Hypothesismentioning

confidence: 94%

Seismic Evidence for Tectonically Dominated Seafloor Spreading in the Southwest Sub‐basin of the South China Sea

Yan

Wang

et al. 2018

Geochem Geophys Geosyst

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Seafloor spreading can be explained by different dynamic mechanisms, magmatically or tectonically dominated. The Southwest Sub‐basin, located at the southwest tip of the propagating seafloor spreading of the South China Sea, remains unclear for its spreading regime owing to poor and debated knowledge of the crustal structures. Here two multichannel seismic lines and one oceanic bottom seismometer line across this subbasin are reprocessed and analyzed with focus on crustal imaging. The sediments are usually 0.5–1.0 km thick over the abyssal basin and slightly thicker in the few grabens. The thickest (3.3 km) sediments are found in the fossil spreading center. The basement is fairly rough and highly faulted by ubiquitous crustal faults. The fossil spreading center is characterized by a deep median valley, similar to that of magma‐poor spreading cases. Both multichannel seismic lines show a few intermittent and diffusive reflectors at 1.5‐ to 3.6‐km depth below the fragmented basement. These reflectors, correlating well with the velocities of 6.8–7.2 km/s obtained from velocity inversion of oceanic bottom seismometer data, are interpreted as Moho reflections. Thus, the inferred crustal thickness is only 1.5–3.6 km excluding the sediments, which is much thinner than usual. The underlying mantle with velocities lower than 8.0 km/s might be serpentinized with water infiltration along these crustal faults. Therefore, it is proposed that the spreading of the Southwest Sub‐basin was tectonically dominated.

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“…Fluids enter the shallow seismogenic system either within the pore space of the subducting igneous crust and sediment, or bound in hydrous minerals. Normal faulting associated with bending of the subducting plate is likely to produce enhanced hydration of the crust and upper mantle seaward of the subduction zone (e.g., Ranero et al, 2003;Naliboff et al, 2013;Korenaga, 2017;Grevemeyer et al, 2018). These fluids are released either through compaction in the shallowest 5-7 km or in dehydration reactions at higher pressures and temperatures (e.g., Saffer and Tobin, 2011).…”

Section: Role Of Megathrust Fluidsmentioning

confidence: 99%

Subduction zone megathrust earthquakes

2018

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Subduction zone megathrust faults host Earth's largest earthquakes, along with multitudes of smaller events that contribute to plate convergence. An understanding of the faulting behavior of megathrusts is central to seismic and tsunami hazard assessment around subduction zone margins. Cumulative sliding displacement across each megathrust, which extends from the trench to the downdip transition to interplate ductile deformation, is accommodated by a combination of rapid stick-slip earthquakes, episodic slow-slip events, and quasi-static creep. Megathrust faults have heterogeneous frictional properties that contribute to earthquake diversity, which is considered here in terms of regional variations in maximum recorded magnitudes, Gutenberg-Richter b values, earthquake productivity, and cumulative seismic moment depth distributions for the major subduction zones. Great earthquakes on megathrusts occur in irregular cycles of interseismic strain accumulation, foreshock activity, main-shock rupture, postseismic slip, viscoelastic relaxation, and fault healing, with all stages now being captured by geophysical monitoring. Observations of depth-dependent radiation characteristics, large earthquake slip distributions, variations in rupture velocities, radiated energy and stress drop, and relationships to aftershock distributions and afterslip are discussed. Seismic sequences for very large events have some degree of regularity within subduction zone segments, but this can be complicated by supercycles of intermittent huge ruptures that traverse segment boundaries. Factors influencing variability of large megathrust ruptures, such as large-scale plate structure and kinematics, presence of sediments and fluids, lower-plate bathymetric roughness, and upper-plate structure, are discussed. The diversity of megathrust failure processes presents a suite of natural hazards, including earthquake shaking, submarine slumping, and tsunami generation. Improved monitoring of the offshore environment is needed to better quantify and mitigate the threats posed by megathrust earthquakes globally.

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Structure of oceanic crust and serpentinization at subduction trenches

Abstract: This paper is published under the terms of the CC-BY-NC license.

Cited by 185 publications

References 105 publications

Geology of the Ionian Basin and Margins: A Key to the East Mediterranean Geodynamics

Geology of the Ionian Basin and Margins: A Key to the East Mediterranean Geodynamics

Seismic Evidence for Tectonically Dominated Seafloor Spreading in the Southwest Sub‐basin of the South China Sea

Subduction zone megathrust earthquakes

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