Deep structure of Iceland and the Iceland-Faeroe-Shetland region based on seismic studies (NASP-72)

Zverev, S. M.; Kosminskaya, I. P.; Krasil'shchikova, G.A.; Mikhota, G. G.

doi:10.1080/00206817709470991

Cited by 16 publications

(27 citation statements)

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“…But the cross section along the NASP profile in some aspects differs from that published by ZVEaEV et al (1976) and KOSMINS-KAYA et al (1977). ZVEREV et al (1976) show a down-dip of the boundary 7 krn/s towards Iceland based on the observed tt increase ( fig. 8 a) and the gravimetrie minimum.…”

Section: Introductionmentioning

confidence: 87%

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Seismic model of Iceland's crust

Павленкова

Zverev

1981

Geol Rundsch

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ZusammenfassungDie Daten der beiden seismischen Langprofile auf Island (NAsr 1972 und RalSP 1977 erlauben Aussagen fiber die tiefere Struktur Islands und deren Zusammenhang mit dem Reykjanes und dem Faeroe-Island-Rficken. Alle tieferen Geschwindigkeitshorizonte fallen vom Ozean her unter Island ein. Die grSl3te unter Island beobachtete Geschwindigkeit betr~igt 7.6--7.7 km/s. Einen komplizierten Verlauf zeigt die 7.0 km/s Geschwindigkeitslinie. Andererseits kann auch Anisotrophie nicht ausgeschlossen werden.Die berechneten seismischen Profile erlauben zwei Interpretationen ffir die Krustenstruktur Islands. Die erste Deutung geht yon einer dfinnen (10---15 km miichtigen) ozeanischen Kruste aus, die direkt yon der domartig aufdringenden Asthenosphere unterlagert wird. Der oberste Bereich der Asthenosphiire ist partiell geschmolzen und zeigt Geschwindigkeiten yon fiber 7.0--7.4 km/s. Die andere, yon den Autoren vertretene Deutung, geht yon einer etwa 80 km m~ichtigen Kruste aus, die auf Mantelmaterial mit Geschwindigkeiten yon 7.5--7.7 km/s liegt. Die Asthenosph~ire folgt erst in 50 km Tiefe. Innerhalb der Kruste ist in 10--15 km Tiefe eine begrenzte Zone mit partiell geschmolzenem Gestein eingelagert, die sich durch eine verringerte Geschwindigkeit der Scherwellen und eine hohe elektrische Leitf~ihigkeit zu erkennen gibt. Die Kruste Islands bildet mit der Faeroe-Island-Rfickens eine Einheit. Ungeachtet der Krustendicke yon 80 kin gehSrt die Kruste Islands aufgrund der basischen Zusammensetzung zum ozeanischen Typ und nicht zum kontinentalen. AbstractThe data of the two long seismic profiles crossing Iceland (NAsP 197"2 and Raise 1977) have revealed its deeper structure and its relation to the Reykjanes and the Faeroe-Iceland Ridge. All deep velocity levels dip down from the ocean towards Iceland. The maximum velocity found on Iceland does not exceed 7.6--7.7 km/s. The 7.0 km/s velocity level is of complex shape. Due to a disagreement of first arrivals at the crosspoint of the two profiles crustal velocity anisotropy may exist. Two different models can be derived from the seismic cross sections. The first model contains a thin oceanic crust being 10---15 km thick. This layer is followed directly by the asthenosphere with velocities near 7.0--7.4 km/s. The top of this diapir-like asthenosphere should be in a partly molten stage. The other version, favoured by the authors, suggests a crust of 80 km thickness which is underlain by mantle material with velocities of 7.5~7.7 km/s. The top of the asthenosphere is assumed to exist in a depth of about 50 km. In the upper crust at 10---15 km depth there occurs a local zone of rocks being in a partly molten stage, as evidenced by the reduced shear wave velocity and the high electrical conductivity. Due to this configuration Iceland forms combined structure with the Faeroe-Iceland Ridge. Despite of its great thickness the crust of Iceland must be regarded as belonging to the oceanic type because of its basic rock composition, thus it is classified as suboceanic.

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Section: Introductionmentioning

confidence: 87%

“…47, no. 1--3, 1980 (1976), andKOSMINSKAYA et al (1977), and those of the RRISP project by the RaIsP Working Group (1980), and by GEBRANDE et al (1980). They derived quite different velocity models for the crust of Iceland, and hence they gave different geological interpretations.…”

Section: Introductionmentioning

confidence: 95%

Seismic model of Iceland's crust

Павленкова

Zverev

1981

Geol Rundsch

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“…Whereas the crust below Iceland was identified as abnormally thick oceanic crust formed by hot-spot activity (Palmason, 1971;Zverev at al., 1976;Gebrande et al, 1980;RRISP, 1980;Staples et al, 1997), the Faeroe block was found to be underlain by 30 km thick continental crust as part of the Caledonides (e.g. Bott et al, 1974).…”

Section: Discussionmentioning

confidence: 99%

“…Iceland is composed of basaltic material with values for v p and v s typical for oceanic crust. The crustal thickness, however, is 4-5 times thicker than normal oceanic crust (Palmason, 1971;Gebrande et al, 1980;RRISP, 1980;Zverev et al, 1976;Staples et al, 1997;Foulger et al, 2003). To the SE the IFR abuts against the Faeroe Islands that have been identified as being of continental origin with a crustal thickness of about 30 km (e.g.…”

Section: Introduction and Tectonic Settingmentioning

confidence: 99%

“…Previous geophysical investigations of the IFR focusing on its crustal structure have revealed contradicting results. Zverev et al (1976) presented a model of thick continental crust below the IFR and Strauch (1970) and McKenna (1972) discussed it as a Tertiary land bridge in the North Atlantic. In contrast, a number of authors (e.g.…”

Section: Introduction and Tectonic Settingmentioning

confidence: 99%

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Crustal structure of the southeastern Iceland-Faeroe Ridge (IFR) from wide aperture seismic data

Bohnhoff¹,

Makris²

2004

Journal of Geodynamics

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The aseismic Iceland-Faeroe-Ridge (IFR) is of central importance in reconstructing the opening of the North Atlantic Ocean. To investigate the crustal structure of the IFR at its southeastern part we conducted a wide aperture seismic survey across the IFR from the Iceland Basin to the Norway Basin. Seismic energy was generated by two 60-litre sleeve guns and recorded by 42 ocean-bottom seismometers (OBS). Kinematic and dynamic forward modeling by two-point ray tracing was applied to develop a 2D velocity-depth model. The accuracy of the model obtained is better than 5% for both velocity and depth of interfaces. We find a Moho depth of 23 km below the crest of the ridge that decreases to about 15 km at either end of the line. The upper part of the crust exhibits P-wave velocities between 5.7 and 6.3 km/s that increase towards the Norway Basin. The lower crust is more homogeneous with v p ranging from 6.6 to 7.0 km/s. Upper and lower parts of the crust are separated by a first order discontinuity. Amplitudes (P m P) and arrival times (P n ) of wide-angle phases indicate upper-mantle velocities of 7.9 km/s. Furthermore we analyzed PS-converted phases for upper crustal depth levels and find a v p /v s ratio of 1.73 AE 0.04 equal to a Poisson's ratio of 0.25 with no significant lateral variations along the seismic line. On the crest of the ridge we identified a basalt layer embedded within the sedimentary sequence that was also penetrated by deep sea drilling and dated to 43AE 3.3 million years. Below the basalt layer we observed a low-velocity layer that is identified as Mesozoic sediment that was also observed to either end of the basalt. We conclude that the southeastern part of the IFR is composed of stretched continental crust and thus part of Paleo-Europe rather than oceanic crust formed by the Iceland hot spot. This conclusion is supported by the distribution of magnetic anomalies that allow identifying the passive continental margin approximately 100 km to the NW of our seismic line. #

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