The source of Proterozoic anorthosite and rapakivi granite magmatism: evidence from combined
            <i>in situ</i>
            Hf–O isotopes of zircon in the Ahvenisto complex, southeastern Finland

Heinonen, Aku; Andersen, Tom; Rämö, O. Tapani; Whitehouse, Martin J.

doi:10.1144/jgs2014-013

Cited by 37 publications

(22 citation statements)

References 48 publications

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“…1.80-1.93 Ga) Svecofennian crust with sharp contacts (Alviola et al, 1999) and according to field relations the felsic rocks are younger than any of the mafic rocks. Isotopic evidence suggests that the primary source of the mafic rocks was most likely asthenospheric depleted mantle and that the felsic rocks were derived from a Proterozoic lower crustal source (Heinonen et al, 2010a(Heinonen et al, , 2010b(Heinonen et al, , 2015. This indicates that the petrogenetic framework of the Ahvenisto complex is congruent with the classical two-source model (Emslie, 1978;Rämö & Haapala, 2005) rather than with the single-source models proposed for some other massif-type anorthositic complexes (Duchesne et al, 1999;Frost & Frost, 1997; see also Heinonen et al, 2010a).…”

Section: Geological Backgroundmentioning

confidence: 90%

“…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%

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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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Section: Geological Backgroundmentioning

confidence: 90%

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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“…Two to four crystals (mainly two) were analyzed from four samples (BD- 14,15,16,17), and up to ten analyses were made for each crystal, in transects from inner growth zone to rim, with closely spaced analyses for S and O isotopes, with a higher number of analyses for O (n = 96) than for S (n = 40). Separate analytical routines applied for S and O, are described briefly below, and closely follow those described in [49] for sulfur, with the exception that only 34 S/ 32 S ratios were measured here, and in [50] for oxygen. For both elements, the samples were sputtered using a Gaussian focused 133 Cs + primary beam with 20 kV incident energy (10 kV primary, −10 kV secondary) and primary beam current of~3 nA, which was rastered over a 5 µm × 5 µm area during analysis to homogenize the beam density.…”

Section: Stable Isotopesmentioning

confidence: 99%

Exceptional Preservation of Fungi as H2-Bearing Fluid Inclusions in an Early Quaternary Paleo-Hydrothermal System at Cape Vani, Milos, Greece

et al. 2019

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The production of H2 in hydrothermal systems and subsurface settings is almost exclusively assumed a result of abiotic processes, particularly serpentinization of ultramafic rocks. The origin of H2 in environments not hosted in ultramafic rocks is, as a rule, unjustifiably linked to abiotic processes. Additionally, multiple microbiological processes among both prokaryotes and eukaryotes are known to involve H2-production, of which anaerobic fungi have been put forward as a potential source of H2 in subsurface environments, which is still unconfirmed. Here, we report fungal remains exceptionally preserved as fluid inclusions in hydrothermal quartz from feeder quartz-barite veins from the Cape Vani Fe-Ba-Mn ore on the Greek island of Milos. The inclusions possess filamentous or near-spheroidal morphologies interpreted as remains of fungal hyphae and spores, respectively. They were characterized by microthermometry, Raman spectroscopy, and staining of exposed inclusions with WGA-FITC under fluorescence microscopy. The spheroidal aqueous inclusions interpreted as fungal spores are unique by their coating of Mn-oxide birnessite, and gas phase H2. A biological origin of the H2 resulting from anaerobic fungal respiration is suggested. We propose that biologically produced H2 by micro-eukaryotes is an unrecognized source of H2 in hydrothermal systems that may support communities of H2-dependent prokaryotes.

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“…After adding a 30 nm gold coating, the oxygen isotope analyses were performed at the NordSIM laboratory, Swedish Museum of Natural History using a Cameca IMS 1280 multicollector-equipped large geometry ion microprobe. The basic instrument setup and analytical protocols closely follow those described by Heinonen et al (2015a) for zircon, staying well within limits on in-run beam centering in the field aperture described by Whitehouse and Nemchin (2009). All data were normalized to regular measurements of the San Carlos olivine that bracketed every six unknown analyses, assuming a δ 18 OV-SMOW of 5.30 ‰, similar to recent measurements using CO2-laser BrF5 fluorination techniques of 5.28 ± 0.04 ‰ (1σ) by Kusakabe & Matsuhisa (2008) and 5.27 ± 0.04 ‰ (2σ) by Ahn et al (2012).…”

Section: Oxygen Isotope and Mineral Chemical Analysismentioning

confidence: 76%

Enrichment of 18O in the mantle sources of the Antarctic portion of the Karoo large igneous province

Heinonen

Luttinen

Whitehouse

2018

Contrib Mineral Petrol

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Karoo continental flood basalt (CFB) province is known for its highly variable trace element and isotopic composition, often attributed to the involvement of continental lithospheric sources. Here we report oxygen isotopic compositions measured with secondary ion mass spectrometry for handpicked olivine phenocrysts from ~190-180 Ma CFBs and intrusive rocks from Vestfjella, western Dronning Maud Land, that forms an Antarctic extension of the Karoo province. The Vestfjella lavas exhibit heterogeneous trace element and radiogenic isotope compositions (e.g., εNd from-16 to +2 at 180 Ma) and the involvement of continental lithospheric mantle and/or crust in their petrogenesis has previously been suggested. Importantly, our sample set also includes rare primitive dikes that have been derived from depleted asthenospheric mantle sources (εNd up to +8 at 180 Ma). The majority of the oxygen isotopic compositions of the olivines from these dike rocks (δ 18 O = 4.4-5.2 ‰; Fo = 78-92 mol. %) are also compatible with such sources. The olivine phenocrysts in the lavas, however, are characterized by notably higher δ 18 O (6.2-7.5 ‰; Fo = 70-88 mol. %) and one of the dike samples gives intermediate compositions (5.2-6.1 ‰, Fo = 83-87 mol. %) between the other dikes and the CFBs. The oxygen isotopic compositions do not correlate with radiogenic isotope compositions susceptible to crustal assimilation (Sr, Nd, and Pb) or with geochemical indicators of pyroxene-rich mantle sources. Instead, δ 18 O correlates positively with enrichments in large-ion lithophile elements (especially K) and 187 Os. We suggest that the oxygen isotopic compositions of the Vestfjella CFB olivines primarily record large-scale subduction-related metasomatism of the sub-Gondwanan mantle (base of the lithosphere or deeper) prior to Karoo magmatism. The overall influence of such sources to Karoo magmatism is not known, but, in addition to continental lithosphere, they may be responsible for some of the geochemical heterogeneity observed in the CFBs.

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The source of Proterozoic anorthosite and rapakivi granite magmatism: evidence from combined in situ Hf–O isotopes of zircon in the Ahvenisto complex, southeastern Finland

Cited by 37 publications

References 48 publications

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

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

Exceptional Preservation of Fungi as H2-Bearing Fluid Inclusions in an Early Quaternary Paleo-Hydrothermal System at Cape Vani, Milos, Greece

Enrichment of 18O in the mantle sources of the Antarctic portion of the Karoo large igneous province

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