Sample records for eudialyte

  1. Eudialyte decomposition minerals with new hitherto undescribed phases from the Ilímaussaq complex, South Greenland


    Karup-Møller, Sven; Rose-Hansen, J.; Sørensen, H


    Eudialyte is a distinctive mineral in the agpaitic group of peralkaline nepheline syenites. The paper describes the alteration of eudialyte from the Ilímaussaq complex, South Greenland, which is the type locality for eudialyte, as well as for agpaitic rocks. Two types of alteration are distinguished: alteration of eudialyte to catapleiite is widespread in the complex, whereas alteration to zircon only occurs in strongly altered rocks. additionally, the fol-lowing minerals have been identified...

  2. Paragenesis and decomposition assemblage of a Mn-rich eudialyte from the Sushina peralkaline nepheline syenite gneiss, Paschim Banga, India (United States)

    Mitchell, Roger H.; Chakrabarty, Aniket


    Proterozoic peralkaline nepheline syenite gneiss occurring at Sushina Hill (Paschim Banga, India) consists of minor eudialyte together with potassium feldspar, albite, aegirine, and nepheline. Perthites are absent and the precursor syenite is considered to have been a two feldspar sub-solidus eudialyte aegirine nepheline syenite . The major minerals have near-endmember compositions and are not altered. In contrast, eudialyte is partially-to-completely altered to a decomposition assemblage consisting principally of hilairite and members of the pectolite-serandite solid solution series together with minor ceriothorianite, pyrochlore, and perraultite. Rinkite occurs as early-forming prismatic inclusions in eudialyte. The eudialyte occurs as an interstitial late-forming magmatic phase with hydrothermal eudialyte overgrowths. Eudialytes from Sushina are characterized by low-to-negligible Fe and high Mn and Nb contents relative to most eudialyte from other localities. Late magmatic eudialyte has relatively high CaO (12-14 wt.%) and low MnO (5.5-7 wt.%) relative to the hydrothermal variety (7-8.5 wt.% CaO; 9.5-10.5 wt.% MnO). The late magmatic Ca-Mn-Nb-rich eudialytes are principally solid solutions between Ce-zirsilite, Mn-taseqite, kentbrooksite, and possibly hydrated eudialyte or aqualite. The Mn-Sr-rich hydrothermal eudialyte is also a solid solution between these end members, although the presence of significant concentrations of Mn at the M(1) site and Sr at the N-site suggests that the mineral could be a new member of the eudialyte group; possibly a Mn analog of taseqite or a Sr analog of manganoeudialyte. The mineralogy of the decomposition assemblage of Sushina eudialyte is unlike those found for other eudialytes and in particular lacks zircon, fergusonite, fluorite and bastnaesite. The deuteric/hydrothermal fluids responsible for the alteration are considered as not buffered by the coexisting silicate assemblage and to be water-rich with very high Na/Cl and Na

  3. Eudialyte decomposition minerals with new hitherto undescribed phases from the Ilímaussaq complex, South Greenland

    DEFF Research Database (Denmark)

    Karup-Møller, Sven; Rose-Hansen, J.; Sørensen, H.


    Eudialyte is a distinctive mineral in the agpaitic group of peralkaline nepheline syenites. The paper describes the alteration of eudialyte from the Ilímaussaq complex, South Greenland, which is the type locality for eudialyte, as well as for agpaitic rocks. Two types of alteration are distinguis......Eudialyte is a distinctive mineral in the agpaitic group of peralkaline nepheline syenites. The paper describes the alteration of eudialyte from the Ilímaussaq complex, South Greenland, which is the type locality for eudialyte, as well as for agpaitic rocks. Two types of alteration...... are distinguished: alteration of eudialyte to catapleiite is widespread in the complex, whereas alteration to zircon only occurs in strongly altered rocks. additionally, the fol-lowing minerals have been identified in the altered eudialyte: aegirine, K-feldspar, albite, analcime, fluorite, monazite, apatite...... in the complex. Alteration to zircon is caused by fluids of external origin or by fluids expelled from intersecting lujavrite and pegmatite dykes. Alteration to catapleiite is caused by late-magmatic interstitial fluids. The alteration has resulted in distinct fractionation of some elements; Zr is, for instance...

  4. Environmental Impacts of Rare Earth Mining and Separation Based on Eudialyte: A New European Way

    Directory of Open Access Journals (Sweden)

    Andrea Schreiber


    Full Text Available Neodymium and dysprosium are two rare earth elements (REEs, out of a group of 17 elements. Due to their unique properties, REEs gained increasing importance in many new technologies, like wind turbines, batteries, etc. However, the production of REEs requires high material and energy consumption and is associated with considerable environmental burdens. Due to the strong dependency of European industry on Chinese REE exports, this paper presents a possible European production chain of REEs based on the mineral eudialyte found in Norra Kärr (Sweden. This European production is compared to a Chinese route, as China produces more than 85% of today’s REEs. Bayan Obo as the largest REE deposit in China is considered as the reference system. Using the life cycle assessment method, the environmental impacts of both production lines are assessed. This study presents newly-estimated data of a possible Swedish eudialyte-based production route for Europe. Results for the new eudialyte process route show reduced environmental burdens, although the total REE content in eudialyte is much smaller than in the Bayan Obo deposit. Especially, the results for dysprosium from eudialyte outreach those for Bayan Obo due to the higher content of heavy rare earth elements.

  5. Alteration of Eudialyte and implications for the REE, ZR, and NB resources of the layered Kakortokites in the ILÍMAUSSAQ intrusion, South West Greenland

    DEFF Research Database (Denmark)

    Borst, Anouk Margaretha; Waight, Tod Earle; Smit, Matthijs Arjen


    The layered kakortokites in the southern part of the Ilímaussaq Intrusion are of great economic interest due to their high concentrations of REE, Zr, Nb and Ta. The prospective metals are largely contained in eudialyte, a complex sodium‐zirconosilicate and one of the major cumulus phases. Eudialy...

  6. New data on eudialyte decomposition minerals from kakortokites and associated pegmatites of the Ilimaussaq complex, South Greenland

    DEFF Research Database (Denmark)

    Karup-Møller, Sven; Rose-Hansen, John


    apatite structure, and Ca-poor A1 with composition (Fe,Mn,Ca)1.5REE6Si6FO22 and unknown structure. Mineral A2 with composition (Ca,Fe)1.2 REE4Si6O19-y(OH)2y.nH2O is indistinguishable from A1 in EMP-backscattered light and has only been found at a limited number of localities. Mineral A2 also occurs...

  7. Recovery of waste and side products of apatite-nepheline and eudialyte ores processing in manufacture of heat-insulating foam glassy-crystalline materials

    Directory of Open Access Journals (Sweden)

    Suvorova O. V.


    Full Text Available Overburden and dressing tailings accumulated in the Murmansk region in impressive volumes represent serious challenges of both economic and ecological character. Maintenance of overburden dumps and dressing tailings involves considerable capital and material expenses. Therefore reprocessing of mining waste and manufacture of building materials, including heat-insulating foam-glass materials, is a promising trend. The work discusses the feasibility of recovering silica-containing waste and ore processing byproducts on the Kola Peninsula. Compositions and techniques for producing blocks and pellets from foam-glass crystalline materials have been developed. The effect of modifying agents on the foam-silicate materials' mechanical properties has been investigated. The production conditions for high-quality foam-silicate blocks have been identified. The foam silicates obtained under optimal conditions have featured a relatively low viscosity (0.3–0.5 g/cm³, high strength (up to 5 MPa and heat conductivity (0.09–0.107 Wt/m·K. Methods of improving the operating characteristics of foam silicates based on structure perfecting have been proposed. It has been found that as a result of shorttime baking of grainy samples the product has a grain strength of 5–6 MPa, density of 0.25–0.35 g/cm3 and a resistance to crushing in cylinder of 2.2–3 MPa, which is 2–3 times higher than that of a material subjected to one-stage thermal treatment. The water absorption of the material is 5–6 %, which is by a half lower compared to a one-stage treated material. The thermal conduction coefficient is 0.091–0.096 Wt/m·K. The obtained materials are recommended for use as heat-insulating surfacing and filling material for garrets, floors and roofs in construction and renovation of industrial and civic buildings

  8. Minerals in nature and "on Paper": History of the commissions on new minerals in Russia and IMA and principles of classification and nomenclature of minerals (United States)

    Bulakh, A. G.


    This paper reviews the history of the foundation of the Commission on New Minerals in Russia (1956) and the same Commission of the International Mineral Association (IMA). The terms mineral species, subspecies, and variety are considered. The nomenclature of mineral groups of lovozerite, eudialyte, and apatite is given as examples of using a root name and its suffixes.

  9. Crystal mat-formation as an igneous layering-forming process: Textural and geochemical evidence from the 'lower layered' nepheline syenite sequence of the Ilímaussaq complex, South Greenland (United States)

    Lindhuber, Matthias J.; Marks, Michael A. W.; Bons, Paul D.; Wenzel, Thomas; Markl, Gregor


    The lower layered nepheline syenite sequence (kakortokites) of the Mesoproterozoic alkaline to peralkaline Ilímaussaq complex, South Greenland shows spectacular rhythmic meter-scale igneous layering. The 29 exposed units have sharp contacts against each other and each of these units consists of three modally graded layers dominated by arfvedsonitic amphibole, eudialyte-group minerals, and alkali feldspar, respectively. This study uses field observations on changes in mineral orientation, recurrent mineral textures, compositional data from eudialyte-group minerals and amphibole, and settling rate calculations based on a modified Stokes' equation to explain the igneous layering of the kakortokites. We propose that the three major cumulus minerals (amphibole, eudialyte s.l., and alkali feldspar) were separated from each other by density contrasts, resulting in modally graded layers within each unit. The densest of these three minerals (amphibole) formed crystal mats within the cooling magma body. These crystal mats acted as barriers that inhibited large-scale vertical migration of melts and crystals with increasing effectiveness over time. The sub-volumes of magma captured in between the crystal mats evolved largely as geochemically independent sub-systems, as indicated by the observed trends in mineral composition.

  10. Singular value decomposition approach to the yttrium occurrence in mineral maps of rare earth element ores using laser-induced breakdown spectroscopy (United States)

    Romppanen, Sari; Häkkänen, Heikki; Kaski, Saara


    Laser-induced breakdown spectroscopy (LIBS) has been used in analysis of rare earth element (REE) ores from the geological formation of Norra Kärr Alkaline Complex in southern Sweden. Yttrium has been detected in eudialyte (Na15 Ca6(Fe,Mn)3 Zr3Si(Si25O73)(O,OH,H2O)3 (OH,Cl)2) and catapleiite (Ca/Na2ZrSi3O9·2H2O). Singular value decomposition (SVD) has been employed in classification of the minerals in the rock samples and maps representing the mineralogy in the sampled area have been constructed. Based on the SVD classification the percentage of the yttrium-bearing ore minerals can be calculated even in fine-grained rock samples.

  11. Exploration of dysprosium: the most critical element for Japan (United States)

    Watanabe, Y.


    Dysprosium (Dy), one of the heavy rare earth elements, is used mainly as an additive for NdFeB permanent magnets which are installed in various modern industrial products such as voice coil motors in computers, factory automation machinery, hybrid and electric vehicles, home electronics, and wind turbine, to improve heat resistance of the magnets. Dy has been produced about 2,000t per year from the ores from ion adsorption type deposits in southern China. However, the produced amount of Dy was significantly reduced in 2011 in China due to reservation of heavy rare earth resources and protection of natural environment, resulting in soaring of Dy price in the world. In order to respond the increasing demand of Dy, unconventional supply sources are inevitably developed, in addition to heavy rare earth enriched ion adsorption type deposits outside China. Heavy rare earth elements including Dy are dominantly hosted in xenotime, fergusonite, zircon, eudialyte, keiviite, kainosite, iimoriite, etc. Concentration of xenotime is found in placer deposits in Malaysia and India, hydrothermal deposits associated with unconformity-type uranium mineralization (Athabasca basin in Canada, Western Australia), iron-oxide fluorite mineralization (South Africa) and Sn-bearing alkaline granite (Brazil). Zircon and fergusontie concentration is found as igneous and hydrothermal products in peralkaline syenite, alkaline granite and pegmatite (e.g., Nechalacho in Canada). Eudialyte concentration is found in some peralkaline syenite bodies in Greenland, Canada, Sweden and Russia. Among these sources, large Dy resources are estimated in the deposits hosted in peralkaline rocks (Nechalacho: 79,000t, Kvanefjeld: 49,000t, Norra Karr: 15,700t, etc.) compared to the present demand of Dy. Thus, Dy will be supplied from the deposits associated with peralkaline and alkaline deposits in future instead of ion adsorption type deposits in southern China.

  12. Magma emplacement and metasomatic processes at the margins of an alkaline intrusion: new insights from the Ilímaussaq intrusion, South Greenland (United States)

    Martin, Craig; Finch, Adrian A.; Hutchison, William; Whyte, Andrew J.; Lynch, Jordan; Meakins, Max


    The Ilímaussaq alkaline complex in south Greenland is one of the largest multiple element resources of REE and U in the world. It is the type locality for agpaitic nepheline syenites (peralkaline rocks, with molar (Na+K)/Al > 1.2, rich in Na-Ca- (Ti, Zr) silicates such as eudialyte group minerals) and an exceptionally well preserved example of extremely evolved alkaline magmatism. Most of the mineral exploration at Ilímaussaq has focused on the upper levels and roof zone of the intrusion (e.g. Kvanfeld, U-mine) where volatiles and highly evolved melts concentrate. However, significant mineralization is also reported around the edge of the intrusion. Here we present new geological and geochemical observations from the eastern contact of the intrusion to evaluate the mechanisms of dyke emplacement and the processes of metasomatism/mineralization at the border of an alkaline igneous intrusion. New geological mapping has allowed us to address the nature of interaction between the agpaitic melts and the adjacent Eriksfjord country rocks, emplacement mechamisms of lujavrites (laminated - arfvedsonite or aegirine - eudialyte nepheline microsyenites) and how they have been emplaced adjacent to the walls of the chamber, in contact the interbedded clastic sediments and lavas of the Eriksfjord formation. Our new detailed geological map, reveals cross-cutting relationships within the complex, between aegirine lujavrite and arfvedsonite lujavrite, that are consistent with multiple stages of magma injection in the emplacement of the agpaitic rocks. Structural and petrological observations show the dimensions and composition of peralkaline dykes that extend up to 300 m from the edges of the intrusion. Mineralisation, interpreted to be caused by late-stage fluids, along a fault that extends over 3 km from the intrusion is used to assess the efficiency of faults and fractures as conduits for fluids to propagate away from the Ilímaussaq complex. Our findings will put one of the

  13. Emplacement and geochemical evolution of highly evolved syenites investigated by a combined structural and geochemical field study: The lujavrites of the Ilímaussaq complex, SW Greenland (United States)

    Ratschbacher, Barbara C.; Marks, Michael A. W.; Bons, Paul D.; Wenzel, Thomas; Markl, Gregor


    Structural mapping and the combined study of magmatic to solid-state deformation textures and mineral compositions in highly evolved nepheline syenites (lujavrites) of the alkaline to peralkaline Ilímaussaq complex (South Greenland) reveal detailed insight into the emplacement and geochemical evolution of the melts they crystallized from. Based on magmatic to solid-state flow textures such as foliations and lineations, we propose that the investigated rock sequence forms a sill-like structure with a steep feeder zone that flattens out over a short distance and intrudes into less evolved overlying units as sub-horizontal sheets by roof uplift. Systematic compositional variation of early-magmatic eudialyte-group minerals (EGM) in the investigated rock sequence monitors the geochemical evolution of the lujavrite-forming melt(s). The chlorine contents of EGM decrease successively upwards within the rock sequence, which probably indicates a successive increase of water activity during differentiation, consistent with a change from sodic pyroxene (aegirine) to sodic amphibole (arfvedsonite) in the mineral assemblage. Both REE contents and Fe/Mn ratios of EGM are promising differentiation indicators, which increase and decrease, respectively, upwards within the sequence due to fractional crystallization. This closed-system evolution is interrupted by a shift towards less evolved melt compositions in one lujavrite unit, for which we assume magma recharge. Our study demonstrates the strength of a combined structural and petrological approach to understand the petrogenesis of an igneous body in more detail and highlights their close connection.

  14. Zr and REE mineralization in sodic lujavrite from the Saima alkaline complex, northeastern China: A mineralogical study and comparison with potassic rocks (United States)

    Wu, Bin; Wang, Ru-Cheng; Yang, Jin-Hui; Wu, Fu-Yuan; Zhang, Wen-Lan; Gu, Xiang-Ping; Zhang, Ai-Cheng


    The Triassic Saima alkaline complex on the Liaodong Peninsula, northeastern China, consists mainly of potassic phonolite, nepheline syenite, and sodic lujavrite. The lujavrite shows significant Zr-REE mineralization, which is present in the form of early magmatic, Zr-REE-enriched clinopyroxene (30%-40%), titanite (5%), and loparite-(Ce), and late magmatic to hydrothermal wadeite, widespread eudialyte group minerals (5%-10%), and catapleiite. Ultimately, the fractionation of the alkaline magma leads to the crystallization of mosandrite and hezuolinite. Textural relations and compositional variation among the characteristic Zr-REE-bearing minerals record that both Zr and REEs were strongly incompatible in the sodic melt, but that Zr mineralization preceded REE mineralization. The main Zr-REE mineralization in the Saima lujavrite resulted from the high peralkalinity, Na/K ratio and HFSE content, low oxygen fugacity, and the intensive activity of water and volatiles of its evolving magma. The discontinuous and abrupt changes in melt composition and mineral assemblage from the potassic nepheline syenite of the complex to the sodic lujavrite suggest that their magma was derived from different episodes of magmatic activity with different physico-chemical characteristics, rather than from the continuous evolution of a single magmatic event.

  15. Layering in peralkaline magmas, Ilímaussaq Complex, S Greenland (United States)

    Hunt, Emma J.; Finch, Adrian A.; Donaldson, Colin H.


    The peralkaline to agpaitic Ilímaussaq Complex, S. Greenland, displays spectacular macrorhythmic (> 5 m) layering via the kakortokite (agpaitic nepheline syenite), which outcrops as the lowest exposed rocks in the complex. This study applies crystal size distribution (CSD) analyses and eudialyte-group mineral chemical compositions to study the marker horizon, Unit 0, and the contact to the underlying Unit - 1. Unit 0 is the best-developed unit in the kakortokites and as such is ideal for gaining insight into processes of crystal formation and growth within the layered kakortokite. The findings are consistent with a model whereby the bulk of the black and red layers developed through in situ crystallisation at the crystal mush-magma interface, whereas the white layer developed through a range of processes operating throughout the magma chamber, including density segregation (gravitational settling and flotation). Primary textures were modified through late-stage textural coarsening via grain overgrowth. An open-system model is proposed, where varying concentrations of halogens, in combination with undercooling, controlled crystal nucleation and growth to form Unit 0. Our observations suggest that the model is applicable more widely to the layering throughout the kakortokite series and potentially other layered peralkaline/agpaitic rocks around the world.

  16. The age and petrogenesis of alkaline magmatism in the Ampasindava Peninsula and Nosy Be archipelago, northern Madagascar (United States)

    Cucciniello, C.; Tucker, R. D.; Jourdan, F.; Melluso, L.; Morra, V.


    The Ampasindava alkaline province consists of a series of circular and elliptical intrusions, lava flows, dyke swarms and plugs of Cenozoic age emplaced into the Mesozoic-Cenozoic sedimentary rocks of the Antsiranana basin (NW Madagascar) and above the crystalline basement. The magmatism in the Ampasindava region is linked to a NW-SE trending extensional tectonic setting. New 40Ar/39Ar age determinations on feldspar separate of alkali granites and basaltic dykes yielded ages of 18.01 ± 0.36 Ma and 26 ± 7 Ma, respectively. Alkali basalts and basanites, nepheline syenites and phonolites, and silica saturated-to-oversaturated syenites, trachytes, granites and rhyolites are the main outcropping lithologies. These rocks have sodic affinity. The felsic rocks are dominant, and range from peraluminous to peralkaline. The mantle-normalized incompatible element patterns of the mafic lavas match those of Na-alkaline lavas in within-plate rift settings. The patterns are identical in shape and absolute concentrations to those of the Bobaomby (Cap d'Ambre) and Massif d'Ambre primitive volcanic rocks. These geochemical features are broadly compatible with variable degrees of partial melting of incompatible element-enriched mantle sources. The mineralogical and geochemical variations are consistent with fractional crystallization processes involving removal of olivine, feldspar, clinopyroxene, amphibole, Fe-Ti oxides and apatite. Removal of small amount of titanite explains the concave upward lanthanide pattern in the evolved nepheline syenites and phonolites, which are additionally rich in exotic silicates typical of agpaitic magmas (eudialyte, F-disilicates).

  17. Geology and genesis of the Toongi rare metal (Zr, Hf, Nb, Ta, Y and REE) deposit, NSW, Australia, and implications for rare metal mineralization in peralkaline igneous rocks (United States)

    Spandler, Carl; Morris, Caitlin


    The Toongi Deposit, located in central NSW, Australia, hosts significant resources of Zr, Hf, Nb, Ta, Y and REE within a small (ca. 0.3 km2), rapidly cooled trachyte laccolith. Toongi is part of regional Late Triassic to Jurassic alkaline magmatic field, but is distinguished from the other igneous bodies by its peralkaline composition and economically significant rare metal content that is homogenously distributed throughout the trachyte body. The primary ore minerals are evenly dispersed throughout the rock and include lueshite/natroniobite and complex Na-Fe-Zr-Nb-Y-REE silicate minerals dominated by a eudialyte group mineral (EGM). The EGM occurs in a unique textural setting in the rock, commonly forming spheroidal or irregular-shaped globules, herein called "snowballs", within the rock matrix. The snowballs are often protruded by aegirine and feldspar phenocrysts and contain swarms of fine aegirine and feldspar grains that often form spiral or swirling patterns within the snowball. Secondary ore minerals include REE carbonates, Y milarite, catapleiite and gaidonnayite that fill fractures and vesicles in the rock. Based on bulk-rock geochemical and Nd isotope data, and thermodynamic modelling of magma fractionation, the alkaline rocks of the region are interpreted to represent extrusive to hyperbyssal products of mantle-derived magma that ponded at mid-crustal levels (ca. 0.3 GPa) and underwent extensive fractionation under low-oxygen fugacity conditions. The high Na2O, peralkaline nature of the Toongi Deposit trachyte developed via extensive fractionation of an alkali olivine basalt parental magma initially in the mid-crust and subsequently at shallow levels (ca. 0.1 GPa). This extended fractionation under low fO2 and relatively low H2O-activity conditions limited volatile release and allowed build-up of rare metal contents to ore grades. We speculate that the ore minerals may have originally formed from rare metal-rich sodic-silicate melt that formed immiscible

  18. Fractionation of Zr and Hf during the differentiation of peralkaline magmatic system (Lovozero rare metal deposit, Kola Peninsula) (United States)

    Kogarko, Liya


    Zirconium and hafnium are valuable strategic metals. We assessed principal features of the distribution of these elements in peralkaline rocks, ores and rock-forming and accessory minerals of Lovozero complex. The accumulation of these elements during the evolution of alkaline magma of Lovozero deposit up to extremely high concentrations in eudialyte ores (5-8% ZrO2 and 1200-1800 ppm Hf) has been established. These ores represent valuable complex raw material not only for Zr and Hf, but for REE as well. We evaluated partition coefficients of these elements in alkaline pyroxenes (aegirines) from porphyry-like agpaitic lujavrites of Lovozero massif which are 0.40 for zirconium and 0.58 for hafnium. We assessed variations of Zr/Hf ratio for all the rocks of Lovozero alkaline massif. The growth of this ratio in the course of the evolution of alkaline magma has been observed from 38 in the earliest magmatic phase, to 44 in the second phase and to 51-53 in the latest manifestation of alkaline magmatsm. On the basis of the obtained data and equations of equilibrium and fractional crystallization the model of the fractionation of zirconium and hafnium during the evolution of Lovozero intrusion has been constructed. We have demonstrated that the source of strongly enriched magmatic systems similar to Lovozero rare metal deposit is short-lived enriched reservoir - metasomatized and carbonatized mantle substrate. We investigated the fractionation of zirconium and hafnium in carbonatized mantle xenoliths from East Antarctica. The elevated Zr/Hf ratios (up to 125) in metasomatized xenoliths by comparison with the chondritic value have been found. The main reactions of carbonate metasomatism lead to the replacement of primary orthopyroxene by clinopyroxene 2Mg2Si2O6 + CaMg(CO3)2 = 2Mg2SiO4 + CaMgSi2O6 + 2CO2 3CaMg(CO3)2 + CaMgSi2O6 = 4CaCO3 + 2Mg2SiO4 + 2CO2 The substantial expansion of the clinopyroxene crystallization field results in increase of Zr/Hf ratio in equilibrium

  19. Lead isotopic evidence for interaction between plume and lower crust during emplacement of peralkaline Lovozero rocks and related rare-metal deposits, East Fennoscandia, Kola Peninsula, Russia (United States)

    Zartman, R. E.; Kogarko, L. N.


    The Lovozero alkaline massif—an agpaitic nepheline syenite layered intrusion—is located in the central part of the Kola Peninsula, Russia, and belongs to the Kola ultramafic alkaline and carbonatitic province (KACP) of Devonian age. Associated loparite and eudialyte deposits, which contain immense resources of REE, Nb, Ta, and Zr, constitute a world class mineral district. Previous Sr, Nd, and Hf isotope investigations demonstrated that these rocks and mineral deposits were derived from a depleted mantle source. However, because the Sr, Nd, and Hf abundances in the Kola alkaline rocks are significantly elevated, their isotopic compositions were relatively insensitive to contamination by the underlying crustal rocks through which the intruding magmas passed. Pb occurring in relatively lower abundance in the KACP rocks, by contrast, would have been a more sensitive indicator of an acquired crustal component. Here, we investigate the lead isotopic signature of representative types of Lovozero rocks in order to further characterize their sources. The measured Pb isotopic composition was corrected using the determined U and Th concentrations to the age of the crystallization of the intrusion (376 ± 28 Ma, based on a 206Pb/204Pb versus 238U/204Pb isochron and 373 ± 9 Ma, from a 208Pb/204Pb versus 232Th/204Pb isochron). Unlike the previously investigated Sr, Nd, and Hf isotopes, the lead isotopic composition plot was well outside the FOZO field. The 206Pb/204Pb values fall within the depleted MORB field, with some rocks having lower 207Pb/204Pb but higher 208Pb/204Pb values. Together with other related carbonatites having both lower and higher 206Pb/204Pb values, the combined KACP rocks form an extended linear array defining either a 2.5-Ga secondary isochron or a mixing line. The projection of this isotopic array toward the very unradiogenic composition of underlying 2.4-2.5-Ga basaltic rocks of the Matachewan superplume and associated Archean granulite facies

  20. Petrogenesis of peralkaline granite dykes of the Straumsvola complex, western Dronning Maud Land, Antarctica (United States)

    Harris, Chris; Dreyer, Tanya; le Roux, Petrus


    Peralkaline syenite and granite dykes cut the Straumsvola nepheline syenite pluton in Western Dronning Maud Land, Antarctica. The average peralkalinity index (PI = molecular Al/[Na + K]) of the dykes is 1.20 ( n = 29) and manifests itself in the presence of the Zr silicates eudialyte, dalyite and vlasovite, and the Na-Ti silicate, narsarsukite. The dykes appear to have intruded during slow cooling of the nepheline syenite pluton, and the petrogenetic relationship of the dykes and the pluton cannot be related to closed-system processes at low pressure, given the thermal divide that exists between silica-undersaturated and oversaturated magmas. Major and trace element variations in the dykes are consistent with a combination of fractional crystallization of parental peralkaline magma of quartz trachyte composition, and internal mineral segregation prior to final solidification. The distribution of accessory minerals is consistent with late-stage crystallization of isolated melt pockets. The dykes give an Rb-Sr isochron age of 171 ± 4.4 Ma, with variable initial 87Sr/86Sr ratio (0.7075 ± 0.0032), and have an average ɛ Nd of - 12.0. Quartz phenocrysts have δ18O values of 8.4-9.2‰, which are generally in O-isotope equilibrium with bulk rock. Differences in the δ18O values of quartz and aegirine (average Δquartz-aegirine = 3.5‰) suggest aegirine formation temperatures around 500 °C, lower than expected for a felsic magma, but consistent with poikilitic aegirine that indicates subsolidus growth. The negative ɛ Nd (values averaging 8.6‰ (assuming Δquartz-magma = 0.6‰) are inconsistent with a magma produced by closed-system fractional crystallization of a mantle-derived magma. By contrast, the nepheline syenite magma had mantle-like δ18O values and much less negative ɛ Nd (average - 3.1, n = 3). The country rock has similar δ18O values to the granite dykes (average 8.0‰, n = 108); this means that models for the petrogenesis of the granites by

  1. Barents Tour for Geotourists (United States)

    Pihlaja, Jouni; Johansson, Peter; Lauri, Laura


    Barents Tour for Geotourists is a guidebook for a circular route locating in northern Finland, northern Norway and north-western Russia. The targets along the route are all connected with different aspects of geology: there are localities presenting rare rock types and minerals, potholes, gorges, eskers, raised beaches and palsa mires. Total number of sites along the route is 26, 14 of them are locating in Finland, 4 in Norway and 8 in the Kola Peninsula, Russia. In addition to geological information on the sites, the guidebook features directions and information on local tourism services in four languages: English, Finnish, Russian and Norwegian. Good examples of the geological sites in northern Finland are the potholes at Aholanvaara, Salla. The largest pothole is called the "Drinking pot". With a diameter of 15.5 m and a depth of 9.5 m it is the largest known pothole in Finland. One famous target in northern Finland is also the Gold Prospector Museum and geological nature trail at Tankavaara, Sodankylä. The museum has an impressive mineral and jewellery stone collection and it is the only international museum in the world displaying past and present items of gold panning and prospecting. The Khibiny Tundra is the largest mountain massif on the Kola Peninsula, Russia. These mountains are best known for their unique landscapes, geology and mineralogy. With an experienced guide, minerals like apatite, nepheline, titanite, eudialyte and lamprophyllite can be found there. In north-eastern Norway, the palsas at Øvre Neiden and Færdesmyra are examples of a specific mire type in the cold climate area. The palsa mires are characterized by the presence of 2-5 m high peat mounds that consist of interleaved peat and ice layers. The route was planned and implemented in the ABCGheritage project (Arctic Biological, Cultural and Geological Heritage) partly funded by the Kolarctic ENPI CBC program of the European Union. The guidebook was written by researchers of the

  2. Genesis of rare-metal pegmatites and alkaline apatite-fluorite rocks of Burpala massi, Northern Baikal folded zone (United States)

    Sotnikova, Irina; Vladykin, Nikolai


    Burpalinsky rare metal alkaline massif in the Northern Baikal folded zone in southern margin of Siberian Platform, is a of intrusion central type, created 287 Ma covering area of about 250 km2. It is composed of nepheline syenites and pulaskites grading to quartz syenites in the contacts. Veines and dykes are represented by shonkinites, sodalite syenite, leucocratic granophyres, alkali granites and numerous rare metal alkaline syenite pegmatites and two dykes of carbonatites. All rocks except for granites are cut by a large apatite-fluorite dyke rocks with mica and magnetite, which in turn is cut by alaskite granites dyke. The massif has been studied by A.M. Portnov, A.A. Ganzeev et al. (1992) Burpalinsky massif is highly enriched with trace elements, which are concentrated in pegmatite dykes. About 70 rare-metal minerals we found in massif. Zr-silicates: zircon, eudialyte, lovenite, Ti-lovenite, velerite, burpalite, seidozerite, Ca- seidozerite, Rosenbuschite, vlasovite, katapleite, Ca-katapleite, elpidite. Ti- minerals:- sphene, astrophyllite, ramsaite, Mn-neptunite bafertisite, chevkinite, Mn-ilmenite, pirofanite, Sr-perrerit, landauite, rutile, anatase, brookite; TR- minerals - loparite, metaloparite, britolite, rinkolite, melanocerite, bastnesite, parisite, ankilite, monazite, fluocerite, TR-apatite; Nb- minerals - pyrochlore, loparite. Other rare minerals leucophanite, hambergite, pyrochlore, betafite, torite, thorianite, tayniolite, brewsterite, cryolite and others. We have proposed a new scheme massif: shonkinites - nepheline syenites - alkaline syenite - quartz syenites - veined rocks: mariupolites, rare-metal pegmatites, apatite, fluorite rock alyaskite and alkaline granites and carbonatites (Sotnikova, 2009). Apatite-fluorite rocks are found in the central part of massif. This is a large vein body of 2 km length and a 20 m width cutting prevailing pulaskites. Previously, these rocks were regarded as hydrothermal low-temperature phase. New geological and