The temporal variation of Mesoarchaean volcanism in the Suomussalmi greenstone belt, Karelia Province, Eastern Finland

Lehtonen, Elina; Heilimo, Esa; Halkoaho, Tapio; Hölttä, Pentti; Huhma, Hannu

doi:10.1007/s00531-016-1327-y

Cited by 5 publications

(4 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The N-S trending 2.9-2.8 Ga Suomussalmi greenstone belt terminates about 10 km south of the Näränkävaara body ( Fig. 2) (Lehtonen et al 2017), and the recently discovered (likely Archean) Takanen greenstone belt also borders the body 2 km to the NW (Iljina 2003). The large SW-NE trending Oulujärvi shear zone crosscuts the NW side of Näränkävaara.…”

Section: Näränkävaara Mafic-ultramafic Bodymentioning

confidence: 97%

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: Näränkävaara Mafic-ultramafic Bodymentioning

confidence: 97%

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

“…The >2.90 Ga rocks in the Finnish part of the Karelia block are restricted to small occurrences of felsic volcanic rocks (ca. 2.93-2.94 Ga) in the Suomussalmi greenstone belt (Huhma et al, 2012a(Huhma et al, , 2012bLehtonen et al, 2017). Instead, komatiites dated at ca.…”

Section: The Re-os Ages and Links To The Regional Geologymentioning

confidence: 99%

Re-Os isotope geochemistry of komatiite-hosted Ni-Cu-PGE deposits in Finland

Moilanen

Hanski

Konnunaho

et al. 2019

Ore Geology Reviews

View full text Add to dashboard Cite

We have studied the Re-Os isotope systematics of komatiite-related Ni-Cu-PGE sulfide deposits in Finland, including the Archean Ruossakero Ni-(Cu), Vaara Ni-(Cu-PGE), Tainiovaara Ni-(Cu-PGE) deposits and Ni-PGE sulfide mineralization related to a dunitic body at Tulppio, and the Paleoproterozoic Lomalampi PGE-(Ni-Cu) deposit. We analyzed chromite separates from both mineralized and non-mineralized komatiitic rocks, bulk-sulfide separates, and country-rock black schist from one deposit, and for comparison, chromite separates from non-mineralized Archean komatiitic rocks from the Kovero and Kuhmo greenstone belts. We have observed open-system behavior of sulfides in three deposits, with their Re-Os isotope compositions indicating resetting at ca. 1.83-1.87 Ga by metamorphic events related to the Svecofennian orogeny. Most of the chromite separates, especially those with >10 ppb Os, retain their primary isotope compositions with near-chondritic initial 187 Os/ 188 Os ratios, indicating that their Os was derived from a mantle source with a chondritic Re-Os isotope evolution. These include the Vaara deposit, which yielded a chromite Re-Os isochron age of 2719 ± 140 Ma and low initial γOs of-1.2 ± 0.02, in spite of the evidence for the presence of mass-independent S isotope fractionation in this deposit, suggesting a low-Os, sulfur-bearing contaminant. In the case of the Lomalampi deposit, chromites yield an isochron with an age of 2058 ± 93 Ma and initial γOs of +0.9 ± 0.02, consistent with earlier isotope data from Central Lapland komatiites. However, one chromite from a mineralized cumulate gave a γOs(2050 Ma) value of +24 ± 18, indicating a minor/moderate degree of crustal contamination involving material from country rock black schists. This is also supported by earlier S isotope data. In the Archean Tainiovaara deposit, chromite also suggests crustal contamination (γOs +13 ± 1), but country rocks are Os-poor Archean gneisses, leaving the source of radiogenic Os unclear, though it is possible that contamination occurred at a greater depth. Our results also provide evidence that the Re-Os age of the Ruossakero deposit is ca. 2.9 Ga, with the deposit likely representing komatiitic magmatism that is older than the komatiitic magmatism elsewhere in Finland. Re-Os results also confirmed that the mineralized Tulppio Dunite is Archean in age. Keywords: Re-Os isotopes; Ni-Cu-PGE sulfide and chromite; komatiite; Archean; Paleoproterozoic; Finland to basaltic (Luolavirta et al., 2017). Another deposit close to Kevitsa, the Sakatti Cu-Ni-PGE sulfide deposit, which is related picritic or komatiitic magmatism (Brownscombe et al., 2015; Makkonen et al., 2017), has a great potential to become economically viable. Experimental work and empirical observations have shown that magmatic sulfide deposits are the products of segregation of an immiscible sulfide-rich liquid from a silicate melt (e.g., Naldrett, 2004, and references therein). The sulfide liquid sequesters chalcophile metals from their parental silicate melt, which may le...

show abstract

“…The volcanic lithologies in the SGB include felsic to ultramafic metavolcanic rocks such as pyroclastic calc-alkaline volcanic rocks, tholeiitic to high-Mg basalts, komatiitic basalts, and komatiites. Zircon U-Pb geochronological studies demonstrate that the SGB was formed between 2.94 and 2.82 Ga (e.g., Lehtonen et al, 2017). The peak metamorphic grade in the eastern Luoma-Saarikylä and Tormua area is mainly in upper amphibolite facies and in the western Kiannanniemi area is low and middle amphibolite-facies (Papunen et al 2009).…”

Section: Komatiites From the Suomussalmi Greenstone Belt In Finlandmentioning

confidence: 99%

Modern ocean island basalt–like 182W signature in Paleoarchean mafic rocks: Implications for the generation, preservation, and destruction of early mantle heterogeneities

Mei

Yang

et al. 2023

Geology

View full text Add to dashboard Cite

Komatiites and picrites generated by high degrees of mantle partial melting serve as potential probes of Earth’s deep mantle. Tungsten (W) isotopes in these rocks offer a rare chance to better understand early differentiation, late accretion, core-mantle interaction, and subsequent evolution of Earth’s mantle. We present new W isotope data for Archean komatiites and basalts from the Barberton (South Africa) and Suomussalmi (Finland) Greenstone Belts and Permian picrites from the Emeishan large igneous province (China). The Paleoarchean samples from the Barberton Greenstone Belt have modern ocean island basalt (OIB)−like μ182W values ranging from −20.4 to +5.6, whereas the Mesoarchean komatiites from the Suomussalmi Greenstone Belt show μ182W values of −2.2 to +11.3. The Permian Emeishan picrites give μ182W values of −7.1 to +3.1. Our data, combined with the published global data set, show that W isotope heterogeneity in the mantle has existed throughout Earth’s history, with positive μ182W values transitioning to near-zero in the upper mantle by the end of the Archean. The negative μ182W values of Paleoarchean samples in the Barberton Greenstone Belt and modern OIBs likely result from either early differentiation or core-mantle interaction. The incorporation of a plume-delivered negative μ182W component and enhanced mantle mixing is a viable mechanism to explain the transition of μ182W values in the upper mantle from positive to near-zero, while recycling of crustal materials into the mantle would result in a shift of negative μ182W values of the lower mantle closer to zero since the onset of plate tectonics. The latter process could possibly explain the slightly negative to near-zero μ182W values of the Emeishan picrites and some kimberlites. The well-resolved negative μ182W anomalies observed in this study provide important insights into the generation, preservation, and obliteration of W isotope heterogeneities in the lower mantle.

show abstract

The temporal variation of Mesoarchaean volcanism in the Suomussalmi greenstone belt, Karelia Province, Eastern Finland

Cited by 5 publications

References 39 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

Re-Os isotope geochemistry of komatiite-hosted Ni-Cu-PGE deposits in Finland

Modern ocean island basalt–like 182W signature in Paleoarchean mafic rocks: Implications for the generation, preservation, and destruction of early mantle heterogeneities

Contact Info

Product

Resources

About