Petrology of Nepheline Syenite Pegmatites in the Oslo Rift, Norway: Zirconium Silicate Mineral Assemblages as Indicators of Alkalinity and Volatile Fugacity in Mildly Agpaitic Magma

Andersen, Tom; Erambert, Muriel; Larsen, Alf Olav; Selbekk, Rune S.

doi:10.1093/petrology/egq058

Cited by 72 publications

(141 citation statements)

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“…In these pegmatites, the primary zirconium and titanium minerals formed during the early, magmatic stage of crystallization (Larsen 2010). In a previous study, Andersen et al (2010) applied chemographic analysis to zirconium silicate mineral assemblages in one group of pegmatites in the LPC, and could confirm the importance of the water, fluorine (HF) and chlorine (HCl) activities for the miaskitic to agpaitic transition in that particular system. However, that study was related only to one of the mineralogically distinct types pegmatites in the complex (Larsen 2010), and did not take the titanium-rich mineral assemblages into account.…”

Section: Introductionmentioning

confidence: 93%

“…Sørensen 1997), but Brøgger (1890) pointed out that volatile components such as fluorine and chlorine in the magma may also have been important for the stabilization of the characteristic Zr and Ti minerals. The factors that control the transition from zirconpresent, miaskitic to zircon-absent agpaitic crystallization regimes have recently been discussed by Andersen et al (2010) and Marks et al (2011).…”

Section: Introductionmentioning

confidence: 99%

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Petrology of nepheline syenite pegmatites in the Oslo Rift, Norway: Zr and Ti mineral assemblages in miaskitic and agpaitic pegmatites in the Larvik Plutonic Complex

et al. 2013

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Abstract. Agpaitic nepheline syenites have complex, Na-Ca-Zr-Ti minerals as the main hosts for zirconium and titanium, rather than zircon and titanite, which are characteristic for miaskitic rocks. The transition from a miaskitic to an agpaitic crystallization regime in silica-undersaturated magma has traditionally been related to increasing peralkalinity of the magma, but halogen and water contents are also important parameters. The Larvik Plutonic Complex (LPC) in the Permian Oslo Rift, Norway consists of intrusions of hypersolvus monzonite (larvikite), nepheline monzonite (lardalite) and nepheline syenite. Pegmatites ranging in composition from miaskitic syenite with or without nepheline to mildly agpaitic nepheline syenite are the latest products of magmatic differentiation in the complex. The pegmatites can be grouped in (at least) four distinct suites from their magmatic Ti and Zr silicate mineral assemblages. Semiquantitative petrogenetic grids for pegmatites in log aNa2SiO5 -log aH2O -log aHF space can be constructed using information on the composition and distribution of minerals in the pegmatites, including the Zr-rich minerals zircon, parakeldyshite, eudialyte, låvenite, wöhlerite, rosenbuschite, hiortdahlite and catapleiite, and the Ti-dominated minerals aenigmatite, zirconolite (polymignite), astrophyllite, lorenzenite, titanite, mosandrite and rinkite. The chemographic analysis indicates that although increasing peralkalinity of the residual magma (given by the activity of the Na2Si2O5 or Nds component) is an important driving force for the miaskitic to agpaitic transition, water, fluoride (HF) and chloride (HCl) activity controls the actual mineral assemblages forming during crystallization of the residual magmas. The most distinctive mineral in the miaskitic pegmatites is zirconolite. At low fluoride activity, parakeldyshite, lorenzenite and wöhlerite are stable in mildly agpaitic systems. High fluorine (or HF) activity favours minerals such as låvenite, hiortdahlite, Unauthenticated Download Date | 5/12/18 1:08 PM 62 rosenbuschite and rinkite, and elevated water activity mosandrite and catapleiite. Astrophyllite and aenigmatite are stable over large ranges of Nds activity, at intermediate and low water activities, respectively.

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Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Petrology of nepheline syenite pegmatites in the Oslo Rift, Norway: Zr and Ti mineral assemblages in miaskitic and agpaitic pegmatites in the Larvik Plutonic Complex

et al. 2013

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“…The results of WDS-EMP analyses on eudialytes have been processed in accordance with Johnsen and Grice [23] and Pfaff et al [52] along with common crystal-chemical principles, as applied by Andersen et al [53,54] Naming end-members is less important than understanding the crystal chemistry of the eudialyte-group minerals, however, an attempt was made to determine the dominant end-members in Norra Kärr eudialyte by following the hierarchical guidelines set up by Johnsen et al [19] as far as possible and by distinguishing end-members by the cation occupancy in the M(1), M (2), and M(3) sites. We have only included the major end-members in this study (Tables 2 and 3).…”

Section: Crystal Chemistry Of the Eudialyte-group Mineralsmentioning

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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“…The accessory mineral assemblage from Monte de Trigo, as well as those from Langesundsfjord and North Qôroq, includes complex Na-Ca-Zr-F silicate minerals, such as wöhlerite and låvenite (Coulson 1997, Andersen et al 2010, which is typical of transitional agpaitic rocks (Sørensen 1997, Andersen et al 2010, Marks et al 2011. This assemblage suggests that the miaskitic to agpaitic transition in the Monte de Trigo alkaline suite follows the increasing fluorine trend of Andersen et al (2010). The EGM crystallization along this fluorine trend, according to these authors, can occur if chlorine or HCl activity is sufficiently high.…”

Section: Petrologic Implicationsmentioning

confidence: 99%

“…Since then, EGMs have been recognized in nearly all occurrences of agpaitic rocks, i.e., peralkaline nepheline syenites (and phonolites) that contain complex silicates of Zr, Ti, REE, F, and other volatiles (Sørensen 1997, Le Maitre 2002. EGMs have been described in agpaitic rocks from Khibiny and Lovozero, Kola Peninsula (Khomyakov 1995, Johnsen & Gault 1997, Schilling et al 2011b); Mont Saint-Hilaire, Canada (Johnsen & Gault 1997, Johnsen & Grice 1999, Schilling et al 2011b); Langesundsfjord, Norway (Andersen et al 2010, Schilling et al 2011b); Tamazeght, Morocco (Schilling et al 2009, Schilling et al 2011b); Poços de Caldas, Brazil (Johnsen & Gault 1997, Ulbrich & Ulbrich 2000, Ulbrich et al 2005, Schilling et al 2011b); Cerro Boggiani, Paraguay (Gomes et al 1996, Carbonin et al 2005; Pilanesberg, South Africa (Mitchell & Liferovich, 2006, Schilling et al 2011a); Sushina Hill, India (Mitchell & Chakrabarty, 2012); Agua de Pau volcano, Azores, Portugal (Ridolfi et al 2003); and Kilombe volcano, Kenya Rift Valley (Ridolfi et al 2006). The typical minerals associated with EGMs include alkali feldspar, nepheline, sodalite, aegirine, arfvedsonite, and several complex Zr-, Nb-, Ti-, and REE-bearing silicates, such as astrophyllite, lamprophyllite, rosenbuschite, rinkite, and wöhlerite (e.g., Sørensen 1997, Andersen et al 2010, Marks et al 2011, Schilling et al 2011b).…”

Section: Introductionmentioning

confidence: 99%

Eudialyte-group minerals from the Monte de Trigo alkaline suite, Brazil: composition and petrological implications

et al. 2016

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ABSTRACT:The Monte de Trigo alkaline suite is a SiO 2 -undersaturated syenite-gabbroid association from the Serra do Mar alkaline province. Eudialyte-group minerals (EGMs) occur in one nepheline microsyenite dyke, associated with aegirine-augite, wöhlerite, låvenite, magnetite, zircon, titanite, britholite, and pyrochlore. Major compositional variations include Si (25.09-25.57 apfu), Nb (0.31-0.76 apfu), Fe (1.40-2.13 apfu), and Mn (1.36-2.08 apfu). The EGMs also contain relatively high contents of Ca (6.13-7.10 apfu), moderate enrichment of rare earth elements (0.38-0.67 apfu), and a relatively low Na content (11.02-12.28 apfu), which can be correlated with their transitional agpaitic assemblage. EGM compositions indicate a complex solid solution that includes eudialyte, kentbrooksite, feklichevite, zirsilite-(Ce), georgbarsanovite, and manganoeudialyte components. EGM trace element analyses show low Sr and Ba contents and a negative Eu/Eu* anomaly, which are interpreted as characteristic of the parental magma due to the previous fractionation of plagioclase and/or alkali feldspar. The EGMs from the dyke border have higher contents of Fe, Sr (2,161-2,699 ppm), Mg (1,179-3,582 ppm), and Zn (732-852 ppm) than those at the dyke center. These differences are related to the incorporation of xenoliths and xenocrysts of melatheralitic host rock into the nephelinesyenitic magma followed by crystal-melt diffusive exchange.KEYWORDS: mineral chemistry; agpaitic rocks; Serra do Mar alkaline province. Ca (6,10 apfu), enriquecimento moderado de elementos terras raras (0,67 apfu) e concentrações relativamente baixas de Na (11,(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)28 de Fe, RESUMO: A suíte alcalina do Monte de Trigo é uma associação sienítico-gabroide que pertence à província alcalina da Serra do Mar. Minerais do grupo da eudialita (EGMs) ocorrem em um dique de nefelina microssienito associados a egirina-augita, wöhlerita, lavenita, magnetita, zircão, titanita, britolita e pirocloro. As principais variações composicionais incluem Si (25,09-25,57 apfu), Nb (0,31-0,76 apfu), Fe (1,40-2,13 apfu) e Mn (1,36-2,08 apfu). Os EGMs também contêm concentrações relativamente altas de

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Petrology of Nepheline Syenite Pegmatites in the Oslo Rift, Norway: Zirconium Silicate Mineral Assemblages as Indicators of Alkalinity and Volatile Fugacity in Mildly Agpaitic Magma

Cited by 72 publications

References 21 publications

Petrology of nepheline syenite pegmatites in the Oslo Rift, Norway: Zr and Ti mineral assemblages in miaskitic and agpaitic pegmatites in the Larvik Plutonic Complex

Petrology of nepheline syenite pegmatites in the Oslo Rift, Norway: Zr and Ti mineral assemblages in miaskitic and agpaitic pegmatites in the Larvik Plutonic Complex

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

Eudialyte-group minerals from the Monte de Trigo alkaline suite, Brazil: composition and petrological implications

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