Crust and upper mantle structure along the DSS Baltic profile in SE Finland

Abstract

S U M M A R YThe 430 km long DSS Baltic profile in SE Finland runs through the Rapakivi intrusion, the Svecokarelian geosynclinal complex, including the Ladoga-Bothnian Bay zone, and the Archean basement complex. A brief description of field operations in 1982 is presented. Record sections of P-and S-waves were used for the interpretations. A starting model was constructed by inverse methods and improved by dynamic ray tracing modelling. Three blocks are indentified on the cross-section from SW to NE. These are the southern, associated with the Rapakivi Massif, depth to Moho (M) about 40 km; the central, Ladoga-Bothnian Bay zone, with M of approximately 55-60 km, and the northern, Archean crystalline basement, with M about 40-45 km. The average crustal velocity is 6.6-6.7 kms-'. The crustal structure along the Baltic profile is compared with the surrounding DSS profiles, Finnish Sveka and Soviet Kern-Tulos and Ladoga profiles. The eastern border of the Ladoga-Bothnian Bay zone was located and specific features of the crust and uppermost mantle along the profile area are discussed.

Can crystallization of olivine tholeiite give rise to potassic rhyolites?—an experimental investigation

“…Similar crustal structure has been found in the Fennoscandian region where plutonic rather than volcanic exposure is the norm. An anomalous high-velocity layer is found at a depth of ∼15 km, underlying the Wiborg batholith (Luosto 1991;Luosto et al 1990). These high-density layers could represent the cumulate residuum left behind following the ascent of residual liquids.…”

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“…P-receiver functions were computed from multiple teleseismic events recorded at each station and H-k stacking (Zhu & Kanamori 2000) and waveform modelling is used in order to extract 2-D crustal models beneath each station. These results are compared with previous models for crustal thickness beneath the region (Luosto et al 1984;Grad & Luosto 1987;Luosto et al 1989Luosto et al , 1990Luosto 1997;Grad et al 2009). This study results in a new Poisson's ratio map and a Moho map which is an improvement on the large scale, reference models of the European crust produced by Kelly et al (2007), EuCRUST-07 of Tesauro et al (2008) and EUNASeis of .…”

Three-dimensional numerical thermal and rheological modelling in the central Fennoscandian Shield

“…1). It was performed as an international co-operation similarly as the later BALTIC profile (e.g., Luosto et al, 1990), which was measured in following summer of 1982. The SVEKA profile was furthermore continued in 1991 and together with the original profile they consist nearly 700 km of seismic soundings crossing the southern and central part of Finland from the Proterozoic to the Archaean domain (e.g., Luosto et al, 1994;Yliniemi et al, 1996).…”

“…These features have been revealed by a numerous geophysical investigations that have been conducted during last few decades. The seismic structure is perhaps best known from several deep seismic sounding (DSS) profiles like BALTIC, SVEKA, FENNIA and BABEL (Grad and Luosto, 1987;Luosto et al, 1990;BABEL Working Group, 1993;FENNIA Working Group, 1998). Also heat flow in the surface and vertical thermal structure have been investigated and modelled quite intensively (e.g., Puranen et al, 1968;Kukkonen, 1993;Jokinen and Kukkonen, 2000).…”