The POLAR Profile revisited: combined P- and S-wave interpretation

Walther, C.; Flüh, Ernst R.

doi:10.1016/0301-9268(93)90073-b

Cited by 21 publications

(16 citation statements)

References 4 publications

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“…12b). This observation is consistent with similar findings from the POLAR profile, approximately 50 km north-west of line 6 (Luosto et al, 1989;Walther and Flüh, 1993;Fig. 1b).…”

Section: Crustal Velocity Structuresupporting

confidence: 93%

“…The Archean bedrock has been surveyed along FINLAP (Luosto et al, 1983) and POLAR (Luosto et al, 1989;Walther and Flüh, 1993;Janik et al, 2009) refraction seismic profiles in northern Finland as well as along Kem-Uchta (Berzin et al, 2002), Kem-Tulos, and Pechenga-Kostomuksha ) refraction profiles in north-western Russia (Fig. 1b).…”

Section: Previous Active Seismic Surveysmentioning

confidence: 99%

See 1 more Smart Citation

Crustal seismic structure and depth distribution of earthquakes in the Archean Kuusamo region, Fennoscandian Shield

Uski¹,

Tiira²,

Grad³

et al. 2012

Journal of Geodynamics

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“…12b). This observation is consistent with similar findings from the POLAR profile, approximately 50 km north-west of line 6 (Luosto et al, 1989;Walther and Flüh, 1993;Fig. 1b).…”

Section: Crustal Velocity Structuresupporting

confidence: 93%

Section: Previous Active Seismic Surveysmentioning

confidence: 99%

Crustal seismic structure and depth distribution of earthquakes in the Archean Kuusamo region, Fennoscandian Shield

Uski¹,

Tiira²,

Grad³

et al. 2012

Journal of Geodynamics

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“…As an example, refraction profiles of 300-500 km length sample the uppermost mantle down to a depth of 70-90 km (Walter & Flueh 1993;EUROBRIDGE Working Group 1999). As an example, refraction profiles of 300-500 km length sample the uppermost mantle down to a depth of 70-90 km (Walter & Flueh 1993;EUROBRIDGE Working Group 1999).…”

Section: O B S E R V a T I O N O F A Z I M U T H A L A N I S O T R O mentioning

confidence: 99%

Seismic anisotropy and mantle creep in young orogens

Meißner¹,

Mooney²,

Artemieva³

2002

Geophysical Journal International

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Summary Seismic anisotropy provides evidence for the physical state and tectonic evolution of the lithosphere. We discuss the origin of anisotropy at various depths, and relate it to tectonic stress, geotherms and rheology. The anisotropy of the uppermost mantle is controlled by the orthorhombic mineral olivine, and may result from ductile deformation, dynamic recrystallization or annealing. Anisotropy beneath young orogens has been measured for the seismic phase Pn that propagates in the uppermost mantle. This anisotropy is interpreted as being caused by deformation during the most recent thermotectonic event, and thus provides information on the process of mountain building. Whereas tectonic stress and many structural features in the upper crust are usually orientated perpendicular to the structural axis of mountain belts, Pn anisotropy is aligned parallel to the structural axis. We interpret this to indicate mountain‐parallel ductile (i.e. creeping) deformation in the uppermost mantle that is a consequence of mountain‐perpendicular compressive stresses. The preferred orientation of the fast axes of some anisotropic minerals, such as olivine, is known to be in the creep direction, a consequence of the anisotropy of strength and viscosity of orientated minerals. In order to explain the anisotropy of the mantle beneath young orogens we extend the concept of crustal ‘escape’ (or ‘extrusion’) tectonics to the uppermost mantle. We present rheological model calculations to support this hypothesis. Mountain‐perpendicular horizontal stress (determined in the upper crust) and mountain‐parallel seismic anisotropy (in the uppermost mantle) require a zone of ductile decoupling in the middle or lower crust of young mountain belts. Examples for stress and mountain‐parallel Pn anisotropy are given for Tibet, the Alpine chains, and young mountain ranges in the Americas. Finally, we suggest a simple model for initiating mountain parallel creep.

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“…In 1985 the contact area of the Karelian craton and Kola province was crossed by the wide‐angle reflection and refraction POLAR profile, with smaller distance between shotpoints than that in the FENNOLORA (Figure 1) [ Luosto et al , 1989; Walther and Flüh , 1993]. Like the FENNOLORA, the POLAR profile was a part of the EGT project.…”

Section: Introductionmentioning

confidence: 99%

“…The study revealed a complicated structure of the crust‐mantle transition beneath the southwest part of the profile, where the upper mantle velocities as large as 8.4–8.7 km/s were revealed [ Luosto et al , 1989; Walther and Flüh , 1993]. Such values are much higher than typical velocities in the depleted peridotitic Archaean mantle.…”

Section: Introductionmentioning

confidence: 99%

Evidence for preservation of crustal root beneath the Proterozoic Lapland‐Kola orogen (northern Fennoscandian shield) derived from P and S wave velocity models of POLAR and HUKKA wide‐angle reflection and refraction profiles and FIRE4 reflection transect

et al. 2009

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[1] We present an analysis of the crust and upper mantle in the northern Fennoscandian shield, based on new P and S wave 2-D velocity models of the POLAR and HUKKA wide-angle reflection and refraction profiles and results of a new seismic reflection experiment in Finland (Finnish Reflection Experiment). The profiles are almost collocated and crossed the Proterozoic Lapland-Kola orogen. A substantial difference of the depth of ''the wide-angle Moho'' (40-42 km) and ''the reflection Moho'' (47-50 km) was found. In order to explain this difference, we compared the velocity models to published values of Vp and Vp/Vs for the main types of lower crustal and mantle rocks. We found that the main reason for disagreement is that the wide-angle Moho and the reflection Moho correspond to different petrological boundaries. In the southwest and northeast portions of the profiles, the wide-angle Moho marks contact of either anorthositic or granulitic lower crust with a reflective layer in the upper mantle composed of peridotites and pyroxenites. The reflection Moho represents the bottom of this lower layer. In the center of the profile the wide-angle Moho marks the top of a large eclogitic body in the upper mantle, representing a well-preserved crustal root beneath the Lapland-Kola orogen formed because of the collision of three former Archaean crustal blocks (terranes or microcontinents). Lack of postorogenic tectonic collapse suggests another mechanism for stabilization of the lithosphere in the area. Upper mantle reflectors at depth of 65-75 km may mark the upper boundary of the cold and mechanically strong Archaean upper mantle wedge. Alternatively, these reflectors may represent a top of uplifted asthenosphere that can explain preservation of crustal root.Citation: Janik, T., E. Kozlovskaya, P. Heikkinen, J. Yliniemi, and H. Silvennoinen (2009), Evidence for preservation of crustal root beneath the Proterozoic Lapland-Kola orogen (northern Fennoscandian shield) derived from P and S wave velocity models of POLAR and HUKKA wide-angle reflection and refraction profiles and FIRE4 reflection transect,

show abstract

The POLAR Profile revisited: combined P- and S-wave interpretation

Cited by 21 publications

References 4 publications

Crustal seismic structure and depth distribution of earthquakes in the Archean Kuusamo region, Fennoscandian Shield

Crustal seismic structure and depth distribution of earthquakes in the Archean Kuusamo region, Fennoscandian Shield

Seismic anisotropy and mantle creep in young orogens

Evidence for preservation of crustal root beneath the Proterozoic Lapland‐Kola orogen (northern Fennoscandian shield) derived from P and S wave velocity models of POLAR and HUKKA wide‐angle reflection and refraction profiles and FIRE4 reflection transect

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