Western Tethys subduction history constrained through upper and lower mantle structure coupled to kinematic reconstruction

Author(s):  
Derya Gürer ◽  
Douwe J J van Hinsbergen ◽  
Douwe van der Meer ◽  
Wim Spakman

<p>A current frontier in paleogeographic and geodynamic research is the reconstruction of the plate tectonic evolution of deep-time ocean basins. However, deep-time plate reconstructions of now-subducted ocean basins are challenging and often result in competing tectonic models, particularly when the upper plate was oceanic and is only preserved as ophiolitic relics. Correlations between paleogeography and tomographically imaged slab remnants has unlocked Earth’s modern mantle structure as an archive for the analysis of such deep-time geological processes. The geology of the western Tethyan realm from Greece to Oman in northeastern Arabia, holds records of the subsequent closure of the Paleo- and Neotethyan oceanic realms and of plates and microcontinents therein due to subduction since the Permian. Kinematic restorations reveal that the western Tethys contained at least three discrete plate systems bounded by transform faults, similar to the Atlantic Ocean today. Previous tomography-geology studies have interpreted the upper and lower mantle structure in terms of subduction history for the Aegean and Arabian segments, but particularly lower mantle structure of the Anatolian segment has not been resolved in detail before. In this segment, kinematic restorations have suggested that at least four subduction zones were responsible for the consumption of oceanic lithosphere, two consuming the Paleotethys, and two consuming the Neotethys. For the Neotethys system, slab segmentation may have led to more than two slab segments in the final mantle architecture. We here interpret the upper, and for the first-time, the lower mantle structure associated with the Anatolian segment, thereby unraveling western Tethys oceanic lithosphere lost to subduction since the Early Triassic, and link this to mantle structure and subduction evolution of the Aegean and Arabian segments. The modern mantle structure as imaged in the tomographic P-wave speed model UU-P07, tested against multi-model vote maps, provides means to find the relics of the complex subduction history and to discern between existing tectonic models. The tomographic  model reveals ten major positive wave speed anomalies interpreted as slab remnants: the previously identified Aegean, Algerian, Emporios, Antalya, Egypt (which is part of the Arabian slabs), Cyprus, Mesopotamia, Al Jawf, and Zagros slabs, and the newly identified Pontide and Herodotus slabs, partly in the upper, but mostly in the lower mantle. We compare the dimensions, locations, and orientations of these slabs with the kinematically-restored subducted area of the Neotethys, and identify the deepest lower mantle anomalies (Emposios, Herodotus, Al Jawf) as remnants of Paleotethys subduction of the three segments, and the remaining anomalies as the expression of complex Neotethys subduction, consistent with recent kinematic restorations of Eastern Mediterranean and Arabian orogenic history. Moreover, we confirm recent findings that the orientation of slabs influences their net sinking rate, with vertical slabs subducted at mantle-stationary trenches sinking faster than flat-lying slabs that once draped the mantle transition zone due to roll-back or trench advance.</p>

2010 ◽  
Vol 47 (4) ◽  
pp. 409-443 ◽  
Author(s):  
Ron M. Clowes ◽  
Don J. White ◽  
Zoltan Hajnal

Within Lithoprobe’s 10 transects, data from more than 20 000 km of multichannel seismic (MCS) reflection profiling and 12 refraction – wide-angle reflection (R/WAR) surveys were acquired. While the main results related to crustal structure, the data also indicated substantial heterogeneity in the lithospheric mantle. Images of fossilized subduction zones from the Eocene to the Neoarchean demonstrate that current plate tectonic processes have been active for more than 2.6 Ga. The Canadian Cordillera has a thin (50–60 km) lithosphere that is likely receiving some dynamic support from the asthenosphere below. Vestiges of the last stage of accretionary tectonic processes that formed the Archean Superior craton are indicated by an unusual anisotropic high velocity layer that may represent relic oceanic lithosphere. Within the Paleoproterozoic Trans-Hudson Orogen, a restricted region of upper mantle P-wave velocity anisotropy is identified with the continental collision between the bounding Hearne and Superior cratons. In the Archean Hearne and Wyoming provinces, two dipping structures within the sub-crustal lithosphere are interpreted as subduction features related to the assembly of the two cratons. Finite-difference modeling of long-offset data (over 1300 km) reveals fine-scale heterogeneities within a layer between 90 and 150 km in the continental lithosphere, perhaps formed through lateral flow or deformation within the upper mantle. Based on Lithoprobe data, heterogeneities within the lithospheric mantle are reasonably common. They have a wide range of seismic signatures, include many different types and show differing scales. Nevertheless, their extent in the lithospheric mantle is considerably less than in the crust.


2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Guido M. Gianni ◽  
César Navarrete ◽  
Silvana Spagnotto

AbstractVertical slab-tearing has been widely reported in modern convergent settings profoundly influencing subduction and mantle dynamics. However, evaluating a similar impact in ancient convergent settings, where oceanic plates have been subducted and the geological record is limited, remains challenging. In this study, we correlate the lower mantle structure, which retained the past subduction configuration, with the upper-plate geological record to show a deep slab rupture interpreted as a large-scale tearing event in the early Mesozoic beneath southwestern Gondwana. For this purpose, we integrated geochronological and geological datasets with P-wave global seismic tomography and plate-kinematic reconstructions. The development of a Late Triassic-Early Jurassic slab-tearing episode supports (i) a slab gap at lower mantle depths, (ii) a contrasting spatiotemporal magmatic evolution, (iii) a lull in arc activity, and (iv) intraplate extension and magmatism in the Neuquén and Colorado basins. This finding not only has implications for identifying past examples of a fundamental process that shapes subduction zones, but also illustrates an additional mechanism to trigger slab-tearing in which plate rupture is caused by opposite rotation of slab segments.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Grace E. Shephard ◽  
Christine Houser ◽  
John W. Hernlund ◽  
Juan J. Valencia-Cardona ◽  
Reidar G. Trønnes ◽  
...  

AbstractThe two most abundant minerals in the Earth’s lower mantle are bridgmanite and ferropericlase. The bulk modulus of ferropericlase (Fp) softens as iron d-electrons transition from a high-spin to low-spin state, affecting the seismic compressional velocity but not the shear velocity. Here, we identify a seismological expression of the iron spin crossover in fast regions associated with cold Fp-rich subducted oceanic lithosphere: the relative abundance of fast velocities in P- and S-wave tomography models diverges in the ~1,400-2,000 km depth range. This is consistent with a reduced temperature sensitivity of P-waves throughout the iron spin crossover. A similar signal is also found in seismically slow regions below ~1,800 km, consistent with broadening and deepening of the crossover at higher temperatures. The corresponding inflection in P-wave velocity is not yet observed in 1-D seismic profiles, suggesting that the lower mantle is composed of non-uniformly distributed thermochemical heterogeneities which dampen the global signature of the Fp spin crossover.


Solid Earth ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 447-462 ◽  
Author(s):  
Anke Dannowski ◽  
Heidrun Kopp ◽  
Frauke Klingelhoefer ◽  
Dirk Klaeschen ◽  
Marc-André Gutscher ◽  
...  

Abstract. The nature of the Ionian Sea crust has been the subject of scientific debate for more than 30 years, mainly because seismic imaging of the deep crust and upper mantle of the Ionian Abyssal Plain (IAP) has not been conclusive to date. The IAP is sandwiched between the Calabrian and Hellenic subduction zones in the central Mediterranean. A NNE–SSW-oriented 131 km long seismic refraction and wide-angle reflection profile, consisting of eight ocean bottom seismometers and hydrophones, was acquired in 2014. The profile was designed to univocally confirm the proposed oceanic nature of the IAP crust as a remnant of the Tethys and to confute its interpretation as a strongly thinned part of the African continental crust. A P-wave velocity model developed from travel-time forward modelling is refined by gravimetric data and synthetic modelling of the seismic data. A roughly 6–7 km thick crust with velocities ranging from 5.1 to 7.2 km s−1, top to bottom, can be traced throughout the IAP. In the vicinity of the Medina seamounts at the southern IAP boundary, the crust thickens to about 9 km and seismic velocities decrease to 6.8 km s−1 at the crust–mantle boundary. The seismic velocity distribution and depth of the crust–mantle boundary in the IAP document its oceanic nature and support the interpretation of the IAP as a remnant of the Tethys lithosphere with the Malta Escarpment as a transform margin and a Tethys opening in the NNW–SSE direction.


Geosphere ◽  
2018 ◽  
Vol 14 (3) ◽  
pp. 907-925 ◽  
Author(s):  
Daniel Evan Portner ◽  
Jonathan R. Delph ◽  
C. Berk Biryol ◽  
Susan L. Beck ◽  
George Zandt ◽  
...  

2021 ◽  
Vol 228 (2) ◽  
pp. 729-743
Author(s):  
Jiaqi Li ◽  
Min Chen ◽  
Jieyuan Ning ◽  
Tiezhao Bao ◽  
Ross Maguire ◽  
...  

SUMMARY The detailed structure near the 410-km discontinuity provides key constraints of the dynamic interactions between the upper mantle and the lower mantle through the mantle transition zone (MTZ) via mass and heat exchange. Meanwhile, the temperature of the subducting slab, which can be derived from its fast wave speed perturbation, is critical for understanding the mantle dynamics in subduction zones where the slab enters the MTZ. Multipathing, i.e. triplicated, body waves that bottom near the MTZ carry rich information of the 410-km discontinuity structure and can be used to constrain the discontinuity depth and radial variations of wave speeds across it. In this study, we systematically analysed the trade-off between model parameters in triplication studies using synthetic examples. Specifically, we illustrated the necessity of using array-normalized amplitude. Two 1-D depth profiles of the wave speed below the Tatar Strait of Russia in the Kuril subduction zone are obtained. We have observed triplications due to both the 410-km discontinuity and the slab upper surface. And, seismic structures for these two interfaces are simultaneously inverted. Our derived 410-km discontinuity depths for the northern and southern regions are at 420$\pm $15 and 425$\pm $15 km, respectively, with no observable uplift. The slab upper surface is inverted to be located about 50–70 km below the 410-km discontinuity. This location is between the depths of the 1 and 2 per cent P-wave speed perturbation contours of a regional 3-D full-waveform inversion (FWI) model, but we found twice the wave speed perturbation amplitude. A wave speed increase of 3.9–4.6 per cent within the slab, compared to 2.0–2.4 per cent from the 3-D FWI model, is necessary to fit the waveforms with the shortest period of 2 s, indicating that high-frequency waves are required to accurately resolve the detailed structures near the MTZ.


2018 ◽  
Author(s):  
Anke Dannowski ◽  
Heidrun Kopp ◽  
Frauke Klingelhoefer ◽  
Dirk Klaeschen ◽  
Marc-André Gutscher ◽  
...  

Abstract. The nature of the Ionian Sea crust has been the subject of scientific debate for more than 30 years, mainly because seismic imaging of the deep crust and upper mantle of the Ionian Abyssal Plain (IAP) has not been conclusive to date. The IAP is sandwiched between the Calabrian and Hellenic subduction zones in the central Mediterranean. To univocally confirm the proposed oceanic nature of the IAP crust as a remnant of the Tethys ocean and to confute its interpretation as a strongly thinned part of the African continental crust, a NE-SW oriented 131 km long seismic refraction and wide-angle reflection profile consisting of eight ocean bottom seismometers and hydrophones was acquired in 2014. A P-wave velocity model developed from travel time forward modelling is refined by gravimetric data and synthetic modelling of the seismic data. A roughly 6 km thick crust with velocities ranging from 5.1 km/s to 7.2 km/s, top to bottom, can be traced throughout the IAP. In the vicinity of the Medina Seamounts at the southern IAP boundary, the crust thickens to about 9 km and seismic velocities decrease to 6.8 km/s at the crust-mantle boundary. The seismic velocity distribution and depth of the crust-mantle boundary in the IAP document its oceanic nature, and support the interpretation of the IAP as a remnant of the Tethys oceanic lithosphere formed during the Permian and Triassic period.


2020 ◽  
Author(s):  
Genti Toyokuni ◽  
Takaya Matsuno ◽  
Dapeng Zhao
Keyword(s):  
P Wave ◽  

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