Zu Hülle, Inhalt, Gefüge und Alter des Alkaligesteinsvorkommen von Norra Kärr im südlichen Mittelschweden

Koark, Hans J.

doi:10.1080/11035896909453661

Cited by 7 publications

(4 citation statements)

References 2 publications

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“…Similar textures are found in lujavrites from the Ilímaussaq complex which has not been subjected to any metamorphism and thus are considered as primary textural features (Ratschbacher et al, 2015). Koark (1960Koark ( , 1968 opined that some features at Norra Kärr, such as the development of the gneissosity, shearing, and folding are the result of the metamorphic overprinting on an igneous lithology. The presence of an albitized zone around the agpaitic rocks of the Sushina Hill complex is also similar to the fenitized zone found at the contact between the catapleiite syenite (grennaite) and Växjö granite at Norra Kärr (Sjöqvist et al, 2013).…”

Section: Geological Settingmentioning

confidence: 79%

Magmatic, hydrothermal and subsolidus evolution of the agpaitic nepheline syenites of the Sushina Hill Complex, India: implications for the metamorphism of peralkaline syenites

et al. 2016

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The Proterozoic Sushina Hill Complex is the only agpaitic complex, reported from India and is characterized by a eudialyte-rinkite-bearing nepheline syenite. The complex is considered a ‘metamorphosed agpaitic complex'. This study describes the mineral assemblages formed during successive stages of evolution from magmatic to hydrothermal stages and low-temperature subsolidus re-equilibration assemblage. The primary-late magmatic assemblage is characterized by albite, orthoclase, unaltered nepheline, zoned diopside-hedenbergite, rinkite, late magmatic eudialyte and magnesio-arfvedsonite formed at ∼700°C with maximum aSiO2 of 0.60. In contrast, a deuteric assemblage (400-348°C) is represented by aegirine-jadeite-rich clinopyroxene, post-magmatic eudialyte, sodalite, analcime and the decomposition assemblages formed after eudialyte with decreasing aSiO2 (0.52-0.48). A further low-temperature subsolidus assemblage (≤250°C) represented by late-forming natrolite could be either related to regressive stages of metamorphism or a continuum of the subsolidus processes. Considering the P/T range of the greenschist - lower-amphibolite facies of metamorphism it is evident that the incorporation of a jadeite component within pyroxene is related to a subsolidus process between ∼400°C and 348°C in a silica deficient environment. We emphasize that the deuteric fluid itself acted as an agent of metamorphism and the decomposition assemblage formed after eudialyte is retained even after metamorphism due to the convergence of subsolidus and metamorphic domains. The formation of jadeite-rich aegirine is not considered to result from metamorphism. Overall it is near-impossible to discern any bona fide metamorphic textures or mineral assemblages in these syenites which appear to preserve a relict mineralogy regardless of their occurrence in country rocks which have experienced greenschist - amphibolite facies metamorphism. The Sushina complex is very similar in this respect to the Norra Kärr complex (Sweden).

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Section: Geological Settingmentioning

confidence: 79%

Magmatic, hydrothermal and subsolidus evolution of the agpaitic nepheline syenites of the Sushina Hill Complex, India: implications for the metamorphism of peralkaline syenites

et al. 2016

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“…Koark critically opposed to this view [38][39][40] and questioned some of the evidence put forth by other authors. After detailed petrofabric studies, his conclusion was that the rocks in Norra Kärr had been deformed.…”

Section: The Norra Kärr Alkaline Complexmentioning

confidence: 99%

Three Compositional Varieties of Rare-Earth Element Ore: Eudialyte-Group Minerals from the Norra Kärr Alkaline Complex, Southern Sweden

et al. 2013

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Agpaitic nepheline syenites at the Norra Kärr Alkaline Complex, southern Sweden, are rich in zirconium and rare-earth elements (REE), which are mainly accommodated in eudialyte-group minerals (EGM). Norra Kärr hosts three compositionally distinct groups of EGM, which are complex zirconosilicates. Analyses of EGM by electron beam energy-dispersive (SEM-EDS) and wavelength-dispersive (WDS-EMP) X-ray microanalysis are presented and compared, complemented by whole-rock analyses. The SEM-EDS and WDS-EMP methods produce comparable results for most elements. Considering that most SEM instruments have a user-friendly EDS system, it is a useful tool for reconnaissance work in research and especially in exploration-related studies. The EGM evolved markedly from an initial Fe-rich and REE-poor, but HREE-dominated variety, to an intermediate Fe-Mn and HREE-rich one, and to a final Mn-and LREE-rich variety, which occur in rocks classified as lakarpite and grennaite. Based on the Mn/(Fe+Mn) ratios of the EGM, this trend is interpreted as a result of magmatic evolution. The threefold diversity of EGM presented in this work is much broader than has previously been documented.

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“…A11 investigatiors agree with a primarily magmatic formation of the rocks, also Koark (1960Koark ( , 1969. Koark has never suggested a metamorphic origin as pretended by v. Eckermann (1968) and taken over by Blaxland (1 977) and Bibikova et al (1980).…”

mentioning

confidence: 80%

“…Since the Rb-Sr isotopic data of rock-forming minerals of two lakarpitic syenites scatter about a 1250 Ma reference line there was at least one geological event disturbing the Rb-Sr isotope systematics on mineral scale (Blaxland 1977). Foliation of the catapleite-eudialyte-nepheline syenite with a preferred orientation of nepheline, aegirine, and albite, as well as reaction fabrics give additional evidence for a metamorphic overprint during Precambrian times, thus excluding a postPrecambrian formation of the complex (Koark 1960(Koark , 1969.…”

mentioning

confidence: 95%

Isotopic composition of galena lead from the Norra Kärr peralkaline complex, Sweden

Kramm¹,

Koark²

1988

Geologiska Föreningen i Stockholm Förhandlingar

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Zu Hülle, Inhalt, Gefüge und Alter des Alkaligesteinsvorkommen von Norra Kärr im südlichen Mittelschweden

Cited by 7 publications

References 2 publications

Magmatic, hydrothermal and subsolidus evolution of the agpaitic nepheline syenites of the Sushina Hill Complex, India: implications for the metamorphism of peralkaline syenites

Magmatic, hydrothermal and subsolidus evolution of the agpaitic nepheline syenites of the Sushina Hill Complex, India: implications for the metamorphism of peralkaline syenites

Three Compositional Varieties of Rare-Earth Element Ore: Eudialyte-Group Minerals from the Norra Kärr Alkaline Complex, Southern Sweden

Isotopic composition of galena lead from the Norra Kärr peralkaline complex, Sweden

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