scholarly journals Eudialyte Group Minerals from the Lovozero Alkaline Massif, Russia: Occurrence, Chemical Composition, and Petrogenetic Significance

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1070
Author(s):  
Julia A. Mikhailova ◽  
Yakov A. Pakhomovsky ◽  
Taras L. Panikorovskii ◽  
Ayya V. Bazai ◽  
Victor N. Yakovenchuk
Keyword(s):  
Chemical Composition ◽  
Nepheline Syenite ◽  
Granite Gneiss ◽  
Lovozero Massif ◽  
Eudialyte Group ◽  
Magmatic Stage ◽  
Late Magmatic Stage ◽  
Volcaniclastic Rocks ◽  
Layered Complex ◽  
Alkaline Massif

The Lovozero Alkaline Massif intruded through the Archean granite-gneiss and Devonian volcaniclastic rocks ca. 360 Ma ago and formed a large laccolith-type body. The lower part of the massif (the Layered complex) is composed of regularly repeating rhythms: melanocratic nepheline syenite (lujavrite, at the top), leucocratic nepheline syenite (foyaite), foidolite (urtite). The upper part of the massif (the Eudialyte complex) is indistinctly layered, and lujavrite enriched with eudialyte-group minerals (EGM) prevails there. In this article, we present the results of a study of the chemical composition and petrography of more than 400 samples of the EGM from the main types of rock of the Lovozero massif. In all types of rock, the EGM form at the late magmatic stage later than alkaline clinopyroxenes and amphiboles or simultaneously with it. When the crystallization of pyroxenes and EGM is simultaneous, the content of ferrous iron in the EGM composition increases. The Mn/Fe ratio in the EGM increases during fractional crystallization from lujavrite to foyaite and urtite. The same process leads to an increase in the modal content of EGM in the foyaite of the Layered complex and to the appearance of primary minerals of the lovozerite group in the foyaite of the Eudialyte complex.

scholarly journals Petrogenesis of the Eudialyte Complex of the Lovozero Alkaline Massif (Kola Peninsula, Russia)

Minerals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 581 ◽  
Author(s):  
Julia A. Mikhailova ◽  
Gregory Yu. Ivanyuk ◽  
Andrey O. Kalashnikov ◽  
Yakov A. Pakhomovsky ◽  
Ayya V. Bazai ◽  
...  
Keyword(s):  
Water Solution ◽  
Granite Gneiss ◽  
Gradual Transition ◽  
Eudialyte Group ◽  
Fine Grained ◽  
Phosphorus Mineralization ◽  
Volcaniclastic Rocks ◽  
Layered Complex ◽  
Alkaline Massif ◽  
Fractionation Path

The Lovozero Alkaline Massif intruded through the Archaean granite-gneiss and Devonian volcaniclastic rocks about 360 million years ago, and formed a large (20 × 30 km) laccolith-type body, rhythmically layered in its lower part (the Layered Complex) and indistinctly layered and enriched in eudialyte-group minerals in its upper part (the Eudialyte Complex). The Eudialyte Complex is composed of two groups of rocks. Among the hypersolvus meso-melanocratic alkaline rocks (mainly malignite, as well as shonkinite, melteigite, and ijolite enriched with the eudialyte-group minerals, EGM), there are lenses of subsolvus leucocratic rocks (foyaite, fine-grained nepheline syenite, urtite with phosphorus mineralization, and primary lovozerite-group minerals). Leucocratic rocks were formed in the process of the fractional crystallization of melanocratic melt enriched in Fe, high field strength elements (HFSE), and halogens. The fractionation of the melanocratic melt proceeded in the direction of an enrichment in nepheline and a decrease in the aegirine content. A similar fractionation path occurs in the Na2O-Al2O3-Fe2O3-SiO2 system, where the melt of the “ijolite” type (approximately 50% of aegirine) evolves towards “phonolitic eutectic” (approximately 10% of aegirine). The temperature of the crystallization of subsolvus leucocratic rocks was about 550 °C. Hypersolvus meso-melanocratic rocks were formed at temperatures of 700–350 °C, with a gradual transition from an almost anhydrous HFSE-Fe-Cl/F-rich alkaline melt to a Na(Cl, F)-rich water solution. Devonian volcaniclastic rocks underwent metasomatic treatment of varying intensity and survived in the Eudialyte Complex, some remaining unchanged and some turning into nepheline syenites. In these rocks, there are signs of a gradual increase in the intensity of alkaline metasomatism, including a wide variety of zirconium phases. The relatively high fugacity of fluorine favored an early formation of zircon in apo-basalt metasomatites. The ensuing crystallization of aegirine in the metasomatites led to an increase in alkali content relative to silicon and parakeldyshite formation. After that, EGM was formed, under the influence of Ca-rich solutions produced by basalt fenitization.

scholarly journals Agpaitic Alkaline Rocks in Southern Brazilian Platform: A Review

Minerals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 934
Author(s):  
Celso de Barros Gomes ◽  
Rogério Guitarrari Azzone ◽  
Gaston Eduardo Enrich Rojas ◽  
Vincenza Guarino ◽  
Excelso Ruberti
Keyword(s):  
South America ◽  
General Information ◽  
Early Triassic ◽  
Southern Brazil ◽  
Fine Grained ◽  
Mineral Assemblages ◽  
Magmatic Stage ◽  
Poços De Caldas ◽  
Late Magmatic Stage ◽  
Alkaline Massif

General information is presented on ten agpaitic occurrences located in southern Brazil and at the border between Brazil and Paraguay. All the Brazilian agpaitic rocks are Late Cretaceous in age, whereas the Paraguayan ones are older than Early Triassic. The most significant occurrence is Poços de Caldas, the largest alkaline massif in South America. In general, these agpaitic rocks contain mineral assemblages that indicate presence of typical halogen-bearing Na–Ca–HFSE phases, eudialyte-, rinkite- and wöhlerite-group minerals being the most frequent ones. However, these associations are indeed more complex in terms of composition, with accessory phases in some cases consisting of various minerals, including U–Th oxides/silicates, Nb oxides, REE–Sr–Ba bearing carbonates–fluorocarbonates–phosphates–silicates and Zr–Na rich silicates. They usually form late magmatic stage to hydrothermal/deuteric assemblages linked with coarse and fine-grained, mainly silica-undersaturated evolved rocks. Data also indicate significant differences in type, amount and composition of agpaitic minerals in all investigated occurrences.

scholarly journals Review on the Compositional Variation of Eudialyte-Group Minerals in the Ilímaussaq Complex (South Greenland)

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1011
Author(s):  
Michael A.W. Marks ◽  
Hans G.M. Eggenkamp ◽  
Petya Atanasova ◽  
Felicitas Mundel ◽  
Sascha Kümmel ◽  
...  
Keyword(s):  
Large Scale ◽  
Compositional Variation ◽  
Local Phase ◽  
Magma Evolution ◽  
Data Set ◽  
Secondary Alteration ◽  
Eudialyte Group ◽  
Magmatic Stage ◽  
Late Magmatic Stage ◽  
Alkaline Complexes

We review the compositional variation of eudialyte-group minerals (EGM) from the Ilímaussaq complex in South Greenland. Investigated samples cover all major rock units and associated pegmatites and aplites. The whole data set (>3000 analyses from >250 samples) exhibits variable XMn (0.1–0.5), REE (0.2–1.7 apfu), Nb (0.1–0.4), and Cl contents (0.4–1.6 apfu). Most EGM compositions are Na-rich (13–15 apfu), while deviations to Na-rich but also to Na-poor compositions occur because of a combination of primary features (peralkalinity, water activity) and secondary alteration. During magma evolution, REE contents in EGM cores generally increase and reach their highest contents in the most evolved rock units of the complex. This points to the moderate compatibility of REE in EGM and a bulk D (cEGM/cmelt) value of <1 during magma differentiation. Chlorine contents in EGM cores continuously decrease, and are lowest at the rims of individual crystals, suggesting a continuous decrease of Cl activity in the magmas by large-scale EGM and sodalite extraction during the orthomagmatic stage and water enrichment during the late-magmatic stage. The overall variations of XMn across stratigraphy are only minor and likely influenced by the co-crystallization of sodic pyroxene and amphibole (c.f. aegirine, arfvedsonite) and local phase proportions. Similarly, Nb and Ti contents are influenced by co-crystallizing aenigmatite, rinkite, and others. Their presence buffers Ti and Nb contents to rather constant and low values, while their absence may cause variable enrichment on a local scale. Very low Sr contents (<0.1 apfu) in magmatic EGM from Ilímaussaq are related to the basaltic nature of the parental magmas of the complex, as large-scale plagioclase fractionation occurred prior to the formation of the Ilímaussaq magmas, effectively removing Sr from the system. This is in line with very strong negative Eu anomalies in EGM from Ilímaussaq. Consistently, Sr contents in EGM from alkaline complexes, for which foiditic parental magmas are assumed, are much higher and, in such cases, negative Eu anomalies are generally absent.

scholarly journals Pre-Pegmatite Stage in Peralkaline Magmatic Process: Insights from Poikilitic Syenites from the Lovozero Massif, Kola Peninsula, Russia

Minerals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 974
Author(s):  
Julia A. Mikhailova ◽  
Yakov A. Pakhomovsky ◽  
Olga F. Goychuk ◽  
Andrey O. Kalashnikov ◽  
Ayya V. Bazai ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Kola Peninsula ◽  
Hydrothermal Solution ◽  
Rare Metal ◽  
Lovozero Massif ◽  
Accessory Minerals ◽  
Rare Elements ◽  
Hydrothermal Stage ◽  
Magmatic Stage ◽  
Residual Solution

The Lovozero peralkaline massif (Kola Peninsula, Russia) is widely known for its unique mineral diversity, and most of the rare metal minerals are found in pegmatites, which are spatially associated with poikilitic rocks (approximately 5% of the massif volume). In order to determine the reasons for this relationship, we have investigated petrography and the chemical composition of poikilitic rocks as well as the chemical composition of the rock-forming and accessory minerals in these rocks. The differentiation of magmatic melt during the formation of the rocks of the Lovozero massif followed the path: lujavrite → foyaite → urtite (magmatic stage) → pegmatite (hydrothermal stage). Yet, for peralkaline systems, the transition between magmatic melt and hydrothermal solution is gradual. In the case of the initially high content of volatiles in the melt, the differentiation path was probably as follows: lujavrite → foyaite (magmatic stage) → urtitization of foyaite → pegmatite (hydrothermal stage). Poikilitic rocks were formed at the stage of urtitization, and we called them pre-pegmatites. Indeed, the poikilitic rocks have a metasomatic texture and, in terms of chemical composition, correspond to magmatic urtite. The reason for the abundance of rare metal minerals in pegmatites associated with poikilitic rocks is that almost only one nepheline is deposited during urtitization, whereas during the magmatic crystallization of urtite, rare elements form accessory minerals in the rock and are less concentrated in the residual solution.

scholarly journals Pyrochlore-Group Minerals in the Granite-Hosted Katugin Rare-Metal Deposit, Transbaikalia, Russia

Minerals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 490
Author(s):  
Anastasia E. Starikova ◽  
Ekaterina P. Bazarova ◽  
Valentina B. Savel’eva ◽  
Eugene V. Sklyarov ◽  
Elena A. Khromova ◽  
...  
Keyword(s):  
Nepheline Syenite ◽  
Rare Metal ◽  
Granitic Rocks ◽  
Ore Deposit ◽  
Metal Deposit ◽  
Pyrochlore Group ◽  
Magmatic Stage ◽  
Rare Metal Deposit ◽  
Late Magmatic Stage ◽  
High Concentrations

Pyrochlore group minerals are the main raw phases in granitic rocks of the Katugin complex-ore deposit that stores Nb, Ta, Y, REE, U, Th, Zr, and cryolite. There are three main types: Primary magmatic, early postmagmatic (secondary-I), and late hydrothermal (secondary-II) pyrochlores. The primary magmatic phase is fluornatropyrochlore, which has high concentrations of Na2O (to 10.5 wt.%), F (to 5.4 wt.%), and REE2O3 (to 17.3 wt.%) but also low CaO (0.6–4.3 wt.%), UO2 (to 2.6 wt.%), ThO2 (to 1.8 wt.%), and PbO (to 1.4 wt.%). Pyrochlore of this type is very rare in nature and is limited to a few occurrences: Rare-metal deposits of Nechalacho in syenite and nepheline syenite (Canada) and Mariupol in nepheline syenite (Ukraine). It may have crystallized synchronously with or slightly later than melanocratic minerals (aegirine, biotite, and arfvedsonite) at the late magmatic stage when Fe from the melt became bound, which hindered the crystallization of columbite. Secondary-I pyrochlore follows cracks or replaces primary pyrochlore in grain rims and is compositionally similar to the early phase, except for lower Na2O concentrations (2.8 wt.%), relatively low F (4 wt.%), and less complete A- and Y-sites occupancy. Secondary-II pyrochlore is a product of late hydrothermal alteration, which postdated the formation of the Katugin deposit. It differs in large ranges of elements and contains minor K, Ba, Pb, Fe, and significant Si concentrations but also low Na and F. Its composition mostly falls within the field of hydro- and keno-pyrochlore.

Eudialyte-group minerals in rocks of Lovozero layered complex at Mt. Karnasurt and Mt. Kedykvyrpakhk

2015 ◽  
Vol 57 (7) ◽  
pp. 600-613 ◽  
Author(s):  
G. Yu. Ivanyuk ◽  
Ya. A. Pakhomovsky ◽  
V. N. Yakovenchuk
Keyword(s):  
Eudialyte Group ◽  
Layered Complex

Geochemistry and geochronology of alkaline dykes from the Finero Phlogopite Peridotite (Ivrea-Verbano Zone): insights into the Triassic-Jurassic tectono-magmatic events of the Southern Alps

2021 ◽  
Author(s):  
Abimbola Chris Ogunyele ◽  
Tommaso Giovanardi ◽  
Mattia Bonazzi ◽  
Maurizio Mazzucchelli ◽  
Alberto Zanetti
Keyword(s):  
Continental Crust ◽  
Southern Alps ◽  
Coarse Grained ◽  
Dyke Swarm ◽  
Fine Grained ◽  
Sector Zoning ◽  
Magmatic Stage ◽  
Late Magmatic Stage ◽  
Mesozoic Magmatism ◽  
Peridotite Mantle

&lt;p&gt;The Ivrea-Verbano Zone (IVZ, westernmost sector of the Southern Alps) represents a unique opportunity to investigate the Paleozoic to Mesozoic geodynamic evolution of the Gondwana and Laurasia boundary from the perspective of the lower continental crust. Only recently, the petrochemical record of Triassic-Jurassic magmatism has been recognized. It mainly affected the northernmost tip, the Finero Complex, where the continental crust was tectonically thinned before opening of Alpine Tethys. However, the Mesozoic magmatism in the Finero Complex is still poorly-constrained. Firstly, its extent is largely unknown, because the mantle and crustal intrusives were already enriched by Paleozoic processes. Secondly, Mesozoic melts migration started when the Finero Complex was still placed at P-T conditions typical of a continental crust-mantle transition (1 GPa): this has promoted the reopening of the geochronological clocks in both Paleozoic and Mesozoic rocks, which usually provides wide time intervals. Lastly, the finding of Mesozoic magmatism as composite veins/pods and metasomatised layers has not allowed an exhaustive reconstruction of the primitive melts geochemistry. To place further constraints on such issue, a new dyke swarm cropping out in the Finero Phlogopite Peridotite mantle unit has been investigated. Dykes usually cut at high angle the mantle foliation and are up to 60 cm thick. They are composed by coarse-grained hornblendite to anorthosite, both phlogopite/biotite-bearing. Many dykes are composite, showing variable proportions of hornblendite and anorthosite. In places, the dyke swam was affected by volatiles overpressure as late magmatic stage, which produced plastic flow and development of a porphyroclastic structure by deformation of the early cumulates, with widespread segregation of a fine-grained mica matrix.&lt;/p&gt;&lt;p&gt;Dykes mainly consist of pargasite, phlogopite/biotite, albite (An 8-10), in association with apatite, monazite, ilmenite, zircon, Nb-rich oxides, carbonates. Enrichments in Fe (amphibole and biotite) and Na (plagioclase) suggest segregation from evolved melts, strongly enriched in H&lt;sub&gt;2&lt;/sub&gt;O, P, C. The large LILE and LREE contents in amphiboles, sometimes associated to high Nb, Ta, Zr and Hf concentrations, as well as the mineral assemblage, support an alkaline affinity of the melts. The strongly positive &amp;#949;Hf&lt;sub&gt;t &lt;/sub&gt;(+10) of zircons and the isotopic Sr composition of amphiboles (0.7042) point to a derivation of the melts from mildly enriched sources, possibly located at the crust-mantle interface.&lt;/p&gt;&lt;p&gt;Zircons from anorthosite layers are mostly anhedral fragments. They show homogenous internal structure or sector zoning. Concordant &lt;sup&gt;206&lt;/sup&gt;Pb/&lt;sup&gt;238&lt;/sup&gt;U zircon ages vary from 221 &amp;#177; 9 Ma to 192 &amp;#177; 8 Ma. The results of this study confirm that mantle input to the Southern Alps magmatism was of alkaline affinity from Norian to Sinemurian. A widespread fluids circulation induced by such magmatism at high P-T conditions was likely the main cause of the diffuse geochronological reset towards Mesozoic ages of the northern IVZ.&lt;/p&gt;

Sergevanite, Na15(Ca3Mn3)(Na2Fe)Zr3Si26O72(OH)3·H2O, a new eudialyte-group mineral from the Lovozero alkaline massif, Kola Peninsula

2020 ◽  
Vol 58 (4) ◽  
pp. 421-436 ◽  
Author(s):  
Nikita V. Chukanov ◽  
Sergey M. Aksenov ◽  
Igor V. Pekov ◽  
Dmitriy I. Belakovskiy ◽  
Svetlana A. Vozchikova ◽  
...  
Keyword(s):  
Kola Peninsula ◽  
Structural Data ◽  
New Mineral ◽  
X Ray Diffraction ◽  
Calculated Density ◽  
Eudialyte Group ◽  
Group Mineral ◽  
X Ray ◽  
Mohs Hardness ◽  
Alkaline Massif

ABSTRACT The new eudialyte-group mineral sergevanite, ideally Na15(Ca3Mn3)(Na2Fe)Zr3Si26O72(OH)3·H2O, was discovered in highly agpaitic foyaite from the Karnasurt Mountain, Lovozero alkaline massif, Kola Peninsula, Russia. The associated minerals are microcline, albite, nepheline, arfvedsonite, aegirine, lamprophyllite, fluorapatite, steenstrupine-(Ce), ilmenite, and sphalerite. Sergevanite forms yellow to orange-yellow anhedral grains up to 1.5 mm across and the outer zones of some grains of associated eudialyte. Its luster is vitreous, and the streak is white. No cleavage is observed. The Mohs' hardness is 5. Density measured by equilibration in heavy liquids is 2.90(1) g/cm3. Calculated density is equal to 2.906 g/cm3. Sergevanite is nonpleochroic, optically uniaxial, positive, with ω = 1.604(2) and ε = 1.607(2) (λ = 589 nm). The infrared spectrum is given. The chemical composition of sergevanite is (wt.%; electron microprobe, H2O determined by HCN analysis): Na2O 13.69, K2O 1.40, CaO 7.66, La2O3 0.90, Ce2O3 1.41, Pr2O3 0.33, Nd2O3 0.64, Sm2O3 0.14, MnO 4.15, FeO 1.34, TiO2 1.19, ZrO2 10.67, HfO2 0.29, Nb2O5 1.63, SiO2 49.61, SO3 0.77, Cl 0.23, H2O 4.22, –O=Cl –0.05, total 100.22. The empirical formula (based on 25.5 Si atoms pfu, in accordance with structural data) is H14.46Na13.64K0.92Ca4.22Ce0.27La0.17Nd0.12Pr0.06Sm0.02Mn1.81Fe2+0.58Ti0.46Zr2.67Hf0.04Nb0.38Si25.5S0.30Cl0.20O81.35. The crystal structure was determined using single-crystal X-ray diffraction data. The new mineral is trigonal, space group R3, with a = 14.2179(1) Å, c = 30.3492(3) Å, V = 5313.11(7) Å3, and Z = 3. In the structure of sergevanite, Ca and Mn are ordered in the six-membered ring of octahedra (at the sites M11 and M12), and Na dominates over Fe2+ at the M2 site. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 7.12 (70) (110), 5.711 (43) (202), 4.321 (72) (205), 3.806 (39) (033), 3.551 (39) (220, 027), 3.398 (39) (313), 2.978 (95) (), 2.855 (100) (404). Sergevanite is named after the Sergevan' River, which is near the discovery locality.

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