First seismic evidence for continental subduction beneath the Western Alps

Zhao, Liang; Ambert, Paul; Guillot, Stéphane; Solarino, Stefano; Malusà, Marco G.; Zheng, Tianyu; Aubert, Coralie; Salimbeni, Simone; Dumont, Thierry; Schwartz, Stéphane; Zhu, Rixiang; Wang, Qingchen

doi:10.1130/g36833.1

Cited by 118 publications

(194 citation statements)

References 27 publications

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“…This study used data collected from 527 broadband seismic stations, benefiting from recent opening of European seismic databases, improvement of permanent broadband network, and consequent improvement of data quality. Among these stations, 449 were from several permanent networks distributed by the European Integrated Data Archive (EIDA) European archive (http://webdc.eu/webdc3/; open gray triangles in Figure c), 23 were from the PYROPE experiment [ Chevrot et al ., ] (blue triangles in Figure c), and 55 are from the CIFALPS experiment [ Zhao et al ., ] (red triangles in Figure c). CIFALPS (i.e., China‐Italy‐France Alps Seismic Survey) was a passive seismic transect operated from July 2012 to September 2013, which crosscuts the entire Western Alps (Figure c).…”

Section: Data and Imagingmentioning

confidence: 99%

“…The complex high‐velocity anomaly observed in cross‐section A‐A′ at depth ≥150 km probably reflects a combined effect of the Western Alps and central Alps slabs (Figure a). Along the CIFALPS profile where the station density is high (5–10 km spacing), the high‐velocity anomaly is continuous from the uppermost mantle where it links with the subducted European crust recognized by receiver function imaging [ Zhao et al ., ] (Figure ). A strong low‐velocity anomaly is observed at 100–250 km depth in the upper mantle of the Western Alps, which does not extend to the central Alps east of 8°E (8 in Figure ; see also Figure ).…”

Section: Large‐scale Features Of the P Wave Modelmentioning

confidence: 99%

“…The crustal model estimated by Zhao et al . [] from receiver function imaging complemented with gravity modeling and geological data is shown in the upper part, with green color representing the lower crust. FPT: Frontal Penninic Thrust.…”

Section: Large‐scale Features Of the P Wave Modelmentioning

confidence: 99%

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Continuity of the Alpine slab unraveled by high‐resolution P wave tomography

et al. 2016

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The question of lateral and/or vertical continuity of subducted slabs in active orogens is a hot topic partly due to poorly resolved tomographic data. The complex slab structure beneath the Alpine region is only partly resolved by available geophysical data, leaving many geological and geodynamical issues widely open. Based upon a finite‐frequency kernel method, we present a new high‐resolution tomography model using P wave data from 527 broadband seismic stations, both from permanent networks and temporary experiments. This model provides an improved image of the slab structure in the Alpine region and fundamental pinpoints for the analysis of Cenozoic magmatism, (U)HP metamorphism, and Alpine topography. Our results document the lateral continuity of the European slab from the Western Alps to the central Alps, and the downdip slab continuity beneath the central Alps, ruling out the hypothesis of slab break off to explain Cenozoic Alpine magmatism. A low‐velocity anomaly is observed in the upper mantle beneath the core of the Western Alps, pointing to dynamic topography effects. A NE dipping Adriatic slab, consistent with Dinaric subduction, is possibly observed beneath the Eastern Alps, whereas the laterally continuous Adriatic slab of the Northern Apennines shows major gaps at the boundary with the Southern Apennines and becomes near vertical in the Alps‐Apennines transition zone. Tear faults accommodating opposite‐dipping subductions during Alpine convergence may represent reactivated lithospheric faults inherited from Tethyan extension. Our results suggest that the interpretations of previous tomography results that include successive slab break offs along the Alpine‐Zagros‐Himalaya orogenic belt might be proficiently reconsidered.

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Section: Data and Imagingmentioning

confidence: 99%

Section: Large‐scale Features Of the P Wave Modelmentioning

confidence: 99%

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Continuity of the Alpine slab unraveled by high‐resolution P wave tomography

et al. 2016

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“…Geophysical evidence has recently provided direct evidence that links exhumed UHP rocks at the surface and subducted continental crust at depth (50). There is presently insufficient data to calculate the flux of atmospheric noble gases returned to the surface by exhumed UHP rocks.…”

Section: Recycling Of Atmospheric Ar and Ne In Forearcsmentioning

confidence: 99%

Atmospheric Ar and Ne returned from mantle depths to the Earth’s surface by forearc recycling

Baldwin¹,

Das²

2015

Proc. Natl. Acad. Sci. U.S.A.

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In subduction zones, sediments, hydrothermally altered lithosphere, fluids, and atmospheric gases are transported into the mantle, where ultrahigh-pressure (UHP) metamorphism takes place. However, the extent to which atmospheric noble gases are trapped in minerals crystallized during UHP metamorphism is unknown. We measured Ar and Ne trapped in phengite and omphacite from the youngest known UHP terrane on Earth to determine the composition of Ar and Ne returned from mantle depths to the surface by forearc recycling. An 40 Ar/ 39 Ar age [7.93 ± 0.10 My (1σ)] for phengite is interpreted as the timing of crystallization at mantle depths and indicates that 40 Ar/ 39 Ar phengite ages reliably record the timing of UHP metamorphism. Both phengite and omphacite yielded atmospheric 38 Ar/ 36 Ar and 20 Ne/ 22 Ne. Our study provides the first documentation, to our knowledge, of entrapment of atmospheric Ar and Ne in phengite and omphacite. Results indicate that a subduction barrier for atmosphericderived noble gases does not exist at mantle depths associated with UHP metamorphism. We show that the crystallization age together with the isotopic composition of nonradiogenic noble gases trapped in minerals formed during subsolidus crystallization at mantle depths can be used to unambiguously assess forearc recycling of atmospheric noble gases. The flux of atmospheric noble gas entering the deep Earth through subduction and returning to the surface cannot be fully realized until the abundances of atmospheric noble gases trapped in exhumed UHP rocks are known.subduction | UHP metamorphism | geochronology | noble gas | atmosphere

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“…the ECORS-CROP profile, as interpreted by Mohn et al 2014) and other seismological soundings (e.g. Zhao et al 2015). Compared with the application of such methods to sedimentary basins, the interpretation of these data is at best ambiguous.…”

Section: Introductionmentioning

confidence: 99%

Platform-basin transitions and their role in Alpine-style collision systems: a comparative approach

Bell

Butler

2017

Swiss J Geosci

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The structure of Alpine-type orogenic belts is widely assumed to have been strongly influenced by the inherited structure of the rifted continental margins from which they were formed. The challenge lies in deciphering these influences when orogenic contraction is strong. Contractional deformation in the Kamchia basin (SW Black Sea), caught between the Balkan orogenic belt and the stable Moesian block, has been arrested, preserving the early development of an Alpine-type orogen. We use 3D seismic and well-data to examine the tectonic and stratigraphic structure of this basin. Significant deformation has occurred underwater, through inversion tectonics within the basin itself. However, the basin margin structures have not reactivated. This margin is marked by a low-angle unconformity across which sediment was routed from the platform into the fledgling syn-orogenic basins. Such pathways may explain non-orogen-derived sediment within parts of the ancestral Apennine foredeep, for example. The role of platform margins to focus contractional deformation may have been over-emphasised elsewhere in the Alpine system. Further, the more strongly subsided portions of rifted margins may have accommodated significant contractional deformation through reactivation of basin faults. In the western Alps the complexity of structural juxapositions across thrust sheets in the Brianconnais may reflect these early-orogenic deformations rather than be the product of deformation that happened after tectonic burial.These early deformations are likely to be recorded in early syn-tectonic depositional sequences.

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First seismic evidence for continental subduction beneath the Western Alps

Cited by 118 publications

References 27 publications

Continuity of the Alpine slab unraveled by high‐resolution P wave tomography

Continuity of the Alpine slab unraveled by high‐resolution P wave tomography

Atmospheric Ar and Ne returned from mantle depths to the Earth’s surface by forearc recycling

Platform-basin transitions and their role in Alpine-style collision systems: a comparative approach

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