Crustal Architecture of the Inverted Central Lapland Rift Along the HUKKA 2007 Profile

Tiira, Timo; Janik, Tomasz; Kozlovskaya, Elena; Grad, M.; Korja, T.; Komminaho, Kari; Hegedűs, E.; Kovács, Csaba Attila; Silvennoinen, Hanna; Brückl, Ewald

doi:10.1007/s00024-013-0725-3

Cited by 11 publications

(6 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1) (Alapieti 1982;Iljina & Hanski 2005). The intrusions were emplaced during widespread mantle-driven igneous activity related to extension and rifting of the Archean nucleus of the Fennoscandian shield (Amelin & Semenov 1996;Tiira et al 2014;Huhma et al 2018). In total, approximately 20 early Paleoproterozoic layered intrusions with associated dyke swarms have been found in the NW region of the Fennoscandian shield (Finland, Russia, and Sweden), all with ages between 2.53-2.39 Ga (Alapieti et al 1990;Amelin et al 1995;Vuollo & Huhma 2005;Bayanova et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Parental magma, magmatic stratigraphy, and reef-type PGE enrichment of the 2.44-Ga mafic-ultramafic Näränkävaara layered intrusion, Northern Finland

et al. 2019

View full text Add to dashboard Cite

About 20 mafic-ultramafic layered intrusions in the northern Fennoscandian shield were emplaced during a widespread magmatic event at 2.5-2.4 Ga. The intrusions host orthomagmatic Ni-Cu-PGE and Cr-V-Ti-Fe deposits. We update the magmatic stratigraphy of the 2.44-Ga Näränkävaara mafic-ultramafic body, northeastern Finland, on the basis of new drill core and outcrop observations. The Näränkävaara body consists of an extensive basal dunite (1700 m thick), and a layered series comprising a peridotitic-pyroxenitic ultramafic zone (600 m thick) and a gabbronoritic-dioritic mafic zone (700 m thick). Two reversals are found in the layered series. The composition of the layered series parental magma was approximated using a previously unidentified marginal series gabbronorite. The parental magma was siliceous high-Mg basalt with high MgO, Ni, and Cr, but also high SiO 2 and Zr, which suggests primary magma contamination by felsic crust. Cu/Pd ratio below that of primitive mantle implies PGE-fertility. The structural position of the marginal series indicates that the thick basal dunite represents an older wallrock for the layered intrusion. A subeconomic reef-type PGE-enriched zone is found in the border zone between the ultramafic and mafic zones and has an average thickness of 25 m with 150-250 ppb of Pt + Pd + Au. Offset-type metal distribution and high sulfide tenor (50-300 ppm Pd) and R-factor (10 5) suggest reef formation by sulfide saturation induced by fractional crystallization. The reef-forming process was probably interrupted by influx of magma related to the first reversal. Metal ratios suggest that this replenishing magma was PGE-depleted before emplacement.

show abstract

Section: Introductionmentioning

confidence: 99%

Parental magma, magmatic stratigraphy, and reef-type PGE enrichment of the 2.44-Ga mafic-ultramafic Näränkävaara layered intrusion, Northern Finland

et al. 2019

View full text Add to dashboard Cite

show abstract

“…In Fig. 3, the investigated profiles are shown by white lines (Hirschleber et al 1975;Lund 1979;Guggisberg 1986;Luosto 1986;Grad & Luosto 1987;Luosto et al 1989Luosto et al , 1990Luosto et al , 1994Grad et al 1991;FENNIA Working Group 1998;Uski et al 2012;Tiira et al 2014) and places of sampled velocities are shown by white dots. All velocity -depth relations were sampled at 1-km depth intervals.…”

Section: Average Velocities Reference Model and Time Correctionsmentioning

confidence: 98%

“…The yellow frame shows the area for which an average Moho depth (45.7 km) was calculated. Data were compiled from Hirschleber et al (1975), Lund (1979), Guggisberg (1986), Luosto (1986), Grad & Luosto (1987), EUGENO-S Working Group (1988), Luosto et al (1989Luosto et al ( , 1990Luosto et al ( , 1994, Grad et al (1991), FENNIA Working Group (1998), Uski et al (2012) and Tiira et al (2014). lithosphere and asthenosphere, the original data need to be timecorrected for topography and Moho depth variation for each event and each station location.…”

Section: Average Velocities Reference Model and Time Correctionsmentioning

confidence: 99%

Seismic lithosphere–asthenosphere boundary beneath the Baltic Shield

Grad

Tiira

Olsson

et al. 2014

GFF

View full text Add to dashboard Cite

The problem of the existence of the asthenosphere for old Precambrian cratons is still discussed. In order to study the seismic lithosphere -asthenosphere boundary (LAB) beneath the Baltic Shield, we used records of nine local earthquakes with magnitudes ranging from 2.7 to 5.9. To model the LAB, original data were corrected for topography and Moho depth using a reference model with a 46-km-thick crust. For two northern events at Spitsbergen and Novaya Zemlya, we observe a low-velocity layer, 60 -70-km-thick asthenosphere, and the LAB beneath Barents Sea was found at depth of c. 200 km. Sections for other events show continuous first arrivals of P-waves with no evidence for "shadow zone" in the whole range of registration, which could either be interpreted as the absence of the asthenosphere beneath the central part of the Baltic Shield, or that the LAB in this area occurs deeper (.200 km). The relatively thin low-velocity layer found beneath southern Sweden, 15 km below the Moho, could be interpreted as small-scale lithospheric heterogeneities, rather than asthenosphere. Differentiation of the lower lithosphere velocities beneath the Baltic Shield could be interpreted as regional heterogeneity or as anisotropy of the Baltic Shield lithosphere, with high velocities approximately in the east-west direction, and slow velocities approximately in the south-north direction.

show abstract

“…As an example of an area with a low level of anthropogenic seismic noise, we selected an area located in the Kuusamo Greenstone Belt (KuGB), Finland, because of numerous previous geological and geophysical studies there (Silvennoinen, 1991;Bruneton et al, 2004;Yliniemi et al, 2004;Silvennoinen and Kozlovskaya, 2007;Poli et al, 2012b;Pedersen et al, 2013;Silvennoinen et al, 2014;Tiira et al, 2014;Vinnik et al, 2014, etc.). Moreover, Weihed et al (2005) and Lehtonen and O'Brien (2009) have shown that this area is prospective for gold-and diamond deposits.…”

Section: Kuusamo Greenstone Belt Areamentioning

confidence: 99%

Improving the quality of empirical Green's functions, obtained by cross-correlation of high-frequency ambient seismic noise

et al. 2019

Self Cite

View full text Add to dashboard Cite

Abstract. Studying the uppermost structure of the subsurface is a necessary part of solving many practical problems (exploration of minerals, groundwater studies, geoengineering, etc.). The practical application of active seismic methods for these purposes is not always possible for different reasons, such as logistical difficulties, high cost of work, and a high level of seismic and acoustic noise. That is why developing and improving passive seismic methods is one of the important problems in applied geophysics. In our study, we describe a way of improving the quality of empirical Green's functions (EGFs), evaluated from high-frequency ambient seismic noise, by using the advanced technique of cross-correlation function stacking in the time domain (in this paper we use term “high-frequency” for frequencies higher than 1 Hz). The technique is based on the global optimization algorithm, in which the optimized objective function is a signal-to-noise ratio of an EGF, retrieved at each iteration. In comparison to existing techniques, based, for example, on weight stacking of cross-correlation functions, our technique makes it possible to significantly increase the signal-to-noise ratio and, therefore, the quality of the EGFs. The technique has been tested with the field data acquired in an area with a high level of industrial noise (Pyhäsalmi Mine, Finland) and in an area with a low level of anthropogenic noise (Kuusamo Greenstone Belt, Finland). The results show that the proposed technique can be used for the extraction of EGFs from high-frequency seismic noise in practical problems of mapping of the shallow subsurface, both in areas with high and low levels of high-frequency seismic noise.

show abstract

Crustal Architecture of the Inverted Central Lapland Rift Along the HUKKA 2007 Profile

Cited by 11 publications

References 43 publications

Parental magma, magmatic stratigraphy, and reef-type PGE enrichment of the 2.44-Ga mafic-ultramafic Näränkävaara layered intrusion, Northern Finland

Parental magma, magmatic stratigraphy, and reef-type PGE enrichment of the 2.44-Ga mafic-ultramafic Näränkävaara layered intrusion, Northern Finland

Seismic lithosphere–asthenosphere boundary beneath the Baltic Shield

Improving the quality of empirical Green's functions, obtained by cross-correlation of high-frequency ambient seismic noise

Contact Info

Product

Resources

About