FORMATION AND FRACTIONATION OF HIGH-Al THOLEIITIC MAGMAS IN THE AHVENISTO RAPAKIVI GRANITE - MASSIF-TYPE ANORTHOSITE COMPLEX, SOUTHEASTERN FINLAND

Heinonen, Aku; Rämö, O. Tapani; Mänttäri, Irmeli; Johanson, Bo; Alviola, Reijo

doi:10.3749/canmin.48.4.969

Cited by 30 publications

(47 citation statements)

References 29 publications

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“…150 km NW from the Wiborg and Ahvenisto rapakivi granites. Several earlier geochronological results on the dyke swarms related to Wiborg rapakivi have been reported (Vorma, 1975;Vaasjoki, 1977;Laitakari, 1987;Siivola, 1987;Vaasjoki et al, 1991;Heinonen et al, 2010).…”

Section: Geological Backgroundmentioning

confidence: 85%

“…The most reliable ages are the 1646 ± 6 Ma (U-Pb, zircon) for the Ansio diabase dyke trending N60W (Häme swarm; Laitakari, 1987); the 1635 ± 3 Ma (U-Pb, zircon) for the Nikkari quartz porphyritic dyke (Suomenniemi swarm; Vaasjoki et al, 1991); 1643 ± 5 Ma (U-Pb, zircon) for the Lovasjärvi diabase dyke (Suomenniemi swarm; Siivola, 1987); and 1636 ± 2 Ma (U-Pb, zircon) for the Leviänlahdenvuoret quartz porphyritic dyke (Ahvenisto swarm; Heinonen et al, 2010). These are coeval with a gabbro-anorthosite surrounding the Mäntyharju rapakivi intrusion .…”

Section: Geological Backgroundmentioning

confidence: 99%

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Mesoproterozoic geomagnetic reversal asymmetry in light of new paleomagnetic and geochronological data for the Häme dyke swarm, Finland: Implications for the Nuna supercontinent

Salminen

Κlein

Veikkolainen

et al. 2017

Precambrian Research

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Baltica represents one of the key continents of the Mesoproterozoic supercontinent Nuna forming the core of it together with Laurentia and Siberia. This study presents new geochronological and paleomagnetic data obtained for Häme diabase dyke swarm in southern Finland. New U-Pb (baddeleyite) ages 1642 ± 2 Ma and 1647 ± 14 Ma for two reversely magnetized dykes are acquired. Demagnetization revealed a dual polarity remanent magnetization direction carried by magnetite. The combined normal (N) and reversed (R) polarity direction for 11 dykes (=sites) is D = 355.6°, I =-09.1° (k = 8.6 and α95 = 16.6°) yielding a paleomagnetic pole at 23.6°N, 209.8°E (K = 10.6 and A95 = 14.7°) with Van der Voo value Q = 7. N and R magnetized units for the Häme dyke swarm show asymmetry in declination values, probably caused by an age difference between the dykes. The Geocentric Axial Dipole (GAD) model indicates that all geomagnetic reversals should be symmetric (in inclination), yet it has been noted that this is not always the case (e.g. 1.57 Ga Satakunta and Åland dykes in Baltica). By analyzing global dual polarity paleomagnetic data we show that the GAD model is a valid assumption at 1.7-1.4 Ga and that the asymmetry between some 2 normal and reversed polarities in global dual-polarity data sets appears randomly over time, and does not follow a global trend. Further, we show that in the case of Åland and Satakunta dykes an unremoved secondary magnetization component could explain the obtained asymmetry. GAD assumption is used to reconstruct the core of Nuna on equatorial latitudes using new data for Häme dykes. Paleomagnetic evidence suggest that maximum assembly of Nuna occurred at 1.5 Ga and the dispersal of the core is proposed to be associated with coeval 1.38-1.27 Ga magmatism in its core continents.

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Section: Geological Backgroundmentioning

confidence: 85%

Section: Geological Backgroundmentioning

confidence: 99%

Mesoproterozoic geomagnetic reversal asymmetry in light of new paleomagnetic and geochronological data for the Häme dyke swarm, Finland: Implications for the Nuna supercontinent

Salminen

Κlein

Veikkolainen

et al. 2017

Precambrian Research

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“…Proterozoic AMCG (anorthosite-mangeritecharnokite-granite) complexes are bimodal (maficfelsic) magmatic suites (Emslie, 1978(Emslie, , 1991Ashwal, 1993;Alviola et al, 1999;Heinonen, 2012) in which different types of interactions of mafic and felsic magmas have been recognized as important petrogenetic processes. In the 1.64 Ga Ah venisto rapakivi granite -massif-type anorthosite complex of southeastern Finland (Savolahti, 1956(Savolahti, , 1966Johanson, 1984;Alviola et al, 1999;Heino nen 2012;Heinonen et al, 2010bHeinonen et al, , 2015 interaction of coeval mafic and felsic magmas has led to both mingling and chemical mixing processes. U-Pb geochronology and field relations reveal that in Ahvenisto, most of the mafic rocks are older than the bulk of the granitic rocks (e.g.…”

Section: Introductionmentioning

confidence: 99%

Tracing the styles of mafic-felsic magma interaction: A case study from the Ahvenisto igneous complex, Finland

Fred¹,

Heinonen²,

Heikkilä³

2019

Bull Geol Soc Finland

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The 1.64 Ga Ahvenisto complex, southeastern Finland, is an anorthosite-mangeritecharnokite-granite (AMCG) suite in which diverse interaction styles of coeval mafic and felsic magmas are observed. Commingling, resulting in mafic pillows and net-veined granite dykes, and chemical mixing producing hybrid rocks, are the most common interaction types. Detailed description of the factors that controlled the interaction styles and relationships between involved rock types are provided using targeted mapping, petrography, and geochemical analyses complemented by chemical mixing and melt viscosity modeling. Interaction occurred at intermediate stages in the magmatic evolution of the complex: when the last fractions of mafic (monzodioritic) melts and the earliest fractions of felsic (hornblende granitic) melts existed simultaneously. Differentiation of mafic magma has produced three monzodioritic rock types: 1) olivine monzodiorite (most mafic, Mg# 49-40), 2) ferrodiorite (Mg# 42-33), and 3) massive monzodiorite (most evolved, Mg# 28-27). The types form an evolutionary trend, and each exhibits different style of interaction with coeval hbl-granite resulting from contrasting conditions and properties (temperature, viscosity, composition). The variation in these properties due to magma evolution and relative proportions of interacting magmas dictated the interaction style: interaction between olivine monzodiorites and granite was almost negligible; ferrodiorites intermingled forming pillows with granitic veins intruding them; and chemical mixing of massive monzodiorite and hbl-granite produced hybrid rocks.

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“…The satellitic Ahvenisto (Mäntyharju) complex on the northwestern side of the Wiborg batholith consists mainly of granitic rocks (70%), gabbroic rocks (25%), and monzodiorites (≤5%) (Alviola et al, 1999;Heinonen et al, 2010). The granites include hornblende granite, hornblende-biotite granite, biotite granite, topaz granite, porphyritic aplite, and aplite.…”

Section: Ahvenisto Anorthosite-rapakivi Granite Complexmentioning

confidence: 99%

Mineral Deposits Related to Granitic Rocks

Haapala¹,

Rämö²

2015

Mineral Deposits of Finland

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FORMATION AND FRACTIONATION OF HIGH-Al THOLEIITIC MAGMAS IN THE AHVENISTO RAPAKIVI GRANITE - MASSIF-TYPE ANORTHOSITE COMPLEX, SOUTHEASTERN FINLAND

Cited by 30 publications

References 29 publications

Mesoproterozoic geomagnetic reversal asymmetry in light of new paleomagnetic and geochronological data for the Häme dyke swarm, Finland: Implications for the Nuna supercontinent

Mesoproterozoic geomagnetic reversal asymmetry in light of new paleomagnetic and geochronological data for the Häme dyke swarm, Finland: Implications for the Nuna supercontinent

Tracing the styles of mafic-felsic magma interaction: A case study from the Ahvenisto igneous complex, Finland

Mineral Deposits Related to Granitic Rocks

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