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15 pages, 4051 KiB

Open AccessFeature PaperArticle

The Solid Solution between NaClO₃ and NaBrO₃ Revisited

by Florent Simon, Nicolas Couvrat, Christelle Bilot, Sylvain Marinel, Sylvie Malo and Gérard Coquerel

Minerals 2023, 13(8), 1006; https://doi.org/10.3390/min13081006 - 28 Jul 2023

Viewed by 737

Abstract

NaClO₃ and NaBrO₃ are believed to form a complete solid solution from RT to fusion. The unique solid phase can thus be written: NaClO_3(1−x)-NaBrO_3(x) with: 0 ≤ x ≤ 1. This study shows that at high temperatures, this [...] Read more.

NaClO₃ and NaBrO₃ are believed to form a complete solid solution from RT to fusion. The unique solid phase can thus be written: NaClO_3(1−x)-NaBrO_3(x) with: 0 ≤ x ≤ 1. This study shows that at high temperatures, this statement might be valid. Nevertheless, up to 50 °C, probably up to 160 °C, and even higher temperatures, this is not true when the system is in thermodynamic equilibrium. A large miscibility gap exists at room temperature (RT). This gap could be reduced up to a complete disappearance by fast crystallization, for instance, spray-drying. The necessary conditions to access equilibrium, including homochirality, are also discussed. Full article

(This article belongs to the Special Issue Isomorphism and Solid Solutions of Minerals and Related Compounds)

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20 pages, 5105 KiB

Open AccessArticle

Alteration of Feldspathoids Changes pH of Late-Magmatic Fluids: A Case Study from the Lovozero Peralkaline Massif, Russia

by Julia A. Mikhailova, Yakov A. Pakhomovsky, Lyudmila M. Lyalina and Ekaterina A. Selivanova

Minerals 2023, 13(1), 39; https://doi.org/10.3390/min13010039 - 26 Dec 2022

Cited by 3 | Viewed by 1385

Abstract

The 360-370-Ma-old Lovozero peralkaline massif (NW Russia) is a layered nepheline syenitic–foidolitic pluton. In the rocks of the massif, late-stage (auto)metasomatic alterations of rock-forming minerals are quite intense. We studied the products of the alteration of nepheline and sodalite via microtextural, microprobe, and [...] Read more.

The 360-370-Ma-old Lovozero peralkaline massif (NW Russia) is a layered nepheline syenitic–foidolitic pluton. In the rocks of the massif, late-stage (auto)metasomatic alterations of rock-forming minerals are quite intense. We studied the products of the alteration of nepheline and sodalite via microtextural, microprobe, and spectroscopic methods. We found that these minerals are extensively replaced by the association between natrolite + nordstrandite ± böhmite ± paranatrolite in accordance with the following reactions: 3Nph + 4H₂O → Ntr + Nsd + NaOH; 6Nph + 9H₂O → Ntr + Pntr + 2Nsd + 2NaOH; Sdl + 4H₂O → Ntr + Nsd + NaOH + NaCl, where Nph is nepheline, Ntr is natrolite, Nsd is nordstrandite, Pntr is paranatrolite, and Sdl is sodalite. As a result, about one-third of the sodium from nepheline (and sodalite) is set free and passes into the fluid. This leads to an increase in the Na/Cl ratio and, hence, the pH of the fluid. An increase in pH stabilizes hyperagpaitic minerals (e.g., ussingite, villiaumite, thermonatrite, and trona), which can crystallize in close proximity to pseudomorphized nepheline and sodalite. Thus, the alteration of feldspathoids increases the pH of late-magmatic fluids, which in turn can lead to the crystallization of hyperagpaitic minerals. Full article

(This article belongs to the Special Issue Isomorphism and Solid Solutions of Minerals and Related Compounds)

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18 pages, 4033 KiB

Open AccessArticle

Iron in Nepheline: Crystal Chemical Features and Petrological Applications

by Julia A. Mikhailova, Sergey M. Aksenov, Yakov A. Pakhomovsky, Bertrand N. Moine, Camille Dusséaux, Yulia A. Vaitieva and Mikhail Voronin

Minerals 2022, 12(10), 1257; https://doi.org/10.3390/min12101257 - 03 Oct 2022

Cited by 4 | Viewed by 1673

Abstract

Nepheline is a nominally anhydrous aluminosilicate that typically contains an impurity of ferric iron replacing aluminum in tetrahedral sites. However, previous researchers noted the constant presence of ferrous iron in the chemical composition of nepheline from the rocks of the Khibiny and Lovozero [...] Read more.

Nepheline is a nominally anhydrous aluminosilicate that typically contains an impurity of ferric iron replacing aluminum in tetrahedral sites. However, previous researchers noted the constant presence of ferrous iron in the chemical composition of nepheline from the rocks of the Khibiny and Lovozero massifs (Kola Peninsula, Russia). We have carried out microprobe, spectroscopic, chemical and crystal chemical studies of nepheline from the Lovozero massif. We have established the presence of molecular water in nepheline, and also that the incorporation of ferrous iron into nepheline crystal structure is associated with the simultaneous increasing of the coordination number from four to five (or six) due to the inclusion of the ‘additional’ water molecules that form point [FeO₄(H₂O)_n]-defects (where n = 1, 2) in the tetrahedral framework. The nepheline iron content is closely related to the presence of small needle-like aegirine inclusions. The total iron content in nepheline saturated with aegirine needles is approximately an order of magnitude lower than in nepheline free from aegirine inclusions. Most likely the aegirine inclusions in nepheline are formed as a result of the decomposition of the nepheline–“iron nepheline” solid solution. We propose that this process is triggered by the oxidation of ferrous iron in the crystal structure of nepheline. Full article

(This article belongs to the Special Issue Isomorphism and Solid Solutions of Minerals and Related Compounds)

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27 pages, 12243 KiB

Open AccessArticle

Fluorine Controls Mineral Assemblages of Alkaline Metasomatites

by Julia A. Mikhailova, Yakov A. Pakhomovsky, Natalia G. Konopleva, Andrey O. Kalashnikov and Victor N. Yakovenchuk

Minerals 2022, 12(9), 1076; https://doi.org/10.3390/min12091076 - 25 Aug 2022

Cited by 1 | Viewed by 1529

Abstract

In the Khibiny and Lovozero alkaline massifs, there are numerous xenoliths of the so-called ‘aluminous hornfelses’ composed of uncommon mineral associations, which, firstly, are ultra-aluminous, and secondly, are highly reduced. (K,Na)-feldspar, albite, hercynite, fayalite, minerals of the phlogopite-annite and cordierite-sekaninaite series, corundum, quartz, [...] Read more.

In the Khibiny and Lovozero alkaline massifs, there are numerous xenoliths of the so-called ‘aluminous hornfelses’ composed of uncommon mineral associations, which, firstly, are ultra-aluminous, and secondly, are highly reduced. (K,Na)-feldspar, albite, hercynite, fayalite, minerals of the phlogopite-annite and cordierite-sekaninaite series, corundum, quartz, muscovite, sillimanite, and andalusite are rock-forming minerals. Fluorite, fluorapatite, ilmenite, pyrrhotite, ulvöspinel, troilite, and native iron are characteristic accessory minerals. The protolith of these rocks is unknown. We studied in detail the petrography, mineralogy, and chemical composition of these rocks and believe that hornfelses were formed as a result of the metasomatic influence of foidolites. The main reason for the formation of an unusual aluminous association is the high mobility of aluminum promoted by the formation of fluid expelled from foidolites of the Na-Al-OH-F complexes. Thus, it is fluorine that controls the mobility of aluminum in the fluid and, consequently, the mineral associations of alkaline metasomatites. The gain of alkalis and aluminum to rocks of protolith was the reason for the intense crystallization of (K,Na)-feldspar. As a result, a SiO₂ deficiency was formed, and Si-poor, Al-rich silicates and/or oxides crystallized. Full article

(This article belongs to the Special Issue Isomorphism and Solid Solutions of Minerals and Related Compounds)

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10 pages, 1369 KiB

Open AccessArticle

On the Isomorphism of Sodium at the M(2) Site in Eudialyte-Group Minerals: The Crystal Structure of Mn-Deficient Manganoeudialyte and the Problem of the Existence of the ^M⁽²⁾Na-Dominant Analogue of Eudialyte

by Sergey M. Aksenov, Nikita V. Chukanov, Igor V. Pekov, Yulia V. Nelyubina, Dmitry A. Varlamov and Lia N. Kogarko

Minerals 2022, 12(8), 949; https://doi.org/10.3390/min12080949 - 28 Jul 2022

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Abstract

Sodium plays an important role in the crystal structures of eudialyte-group minerals given that it can occupy different crystallographic sites. Predominantly, it distributes between the N(1–5) sites situated in the large cavities of the heteropolyhedral framework. Rarely, Na occupies split sites of [...] Read more.

Sodium plays an important role in the crystal structures of eudialyte-group minerals given that it can occupy different crystallographic sites. Predominantly, it distributes between the N(1–5) sites situated in the large cavities of the heteropolyhedral framework. Rarely, Na occupies split sites of the M(2) microregion where it can predominate over other elements (predominantly Mn, Fe²⁺, and Fe³⁺). The crystal structure of the Mn-deficient manganoeudialyte from the Lovozero alkaline complex (Kola Peninsula, Russia) has been refined. The trigonal unit–cell parameters are: a = 14.1848(2) Å, c = 30.4726(3) Å, V = 5309.90(11) Å³. The sample is a rare example of a high-sodium and high-calcium representative of the eudialyte group with Fe + Mn < 2 apfu. The idealized formula is Na₁₄Ca₆[(Mn,Fe)₂Na]Zr₃Si₂[Si₂₄O₇₂]O(OH)·2H₂O with bivalent components, Mn²⁺ and Fe²⁺, dominating at the M(2) site. The regularities of isomorphism involving ^M⁽²⁾Na in EGMs and the problem of the existence of the ^M⁽²⁾Na-dominant analogue of eudialyte are discussed. The new data obtained in this work confirm the previous conclusion that the complete isomorphism between Ca-deficient and Ca-rich members of the eudialyte group cannot be realized in frames of a single-space group (R3m, R-3m or R3). Thus, the existence of the ^M⁽²⁾Na analogue of eudialyte remains questionable. Full article

(This article belongs to the Special Issue Isomorphism and Solid Solutions of Minerals and Related Compounds)

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25 pages, 4421 KiB

Open AccessArticle

Nature and Isomorphism of Extra-Framework Components in Cancrinite- and Sodalite-Related Minerals: New Data

by Nikita V. Chukanov, Marina F. Vigasina, Roman Yu. Shendrik, Dmitry A. Varlamov, Igor V. Pekov and Natalia V. Zubkova

Minerals 2022, 12(6), 729; https://doi.org/10.3390/min12060729 - 07 Jun 2022

Cited by 6 | Viewed by 1732

Abstract

New data on the isomorphism of extra-framework components (including chromophores) in two- and multilayer minerals belonging to the cancrinite and sodalite groups, are obtained using chemical and single-crystal X-ray diffraction data as well as infrared, Raman, ESR, UV–Vis–near IR absorption and photoluminescence spectroscopy [...] Read more.

New data on the isomorphism of extra-framework components (including chromophores) in two- and multilayer minerals belonging to the cancrinite and sodalite groups, are obtained using chemical and single-crystal X-ray diffraction data as well as infrared, Raman, ESR, UV–Vis–near IR absorption and photoluminescence spectroscopy methods. It is shown that the blue color of these minerals may be due to CO₃^•− or S₃^•− radical anions, whereas yellow and pink shadings are typically due to the presence of S₂^•− radical anions and S₄^•− or S₄, respectively. Two kyanoxalite varieties are distinguished: (1) with predominantly acid oxalate groups and (2) predominantly neutral oxalate groups. Zundel cation H₅O₂+ and CO₂ molecules are shown to be typical impurities in nosean. The Zundel cation is also detected in kyanoxalite and in the 12-layer, cancrinite-related mineral marinellite. Wide isomorphic series involving substitutions of SO₄⁻ for SO₃²⁻ and CO₃²⁻, as well as OH⁻ for H₂O and F⁻, are common for eight-layer, cancrinite-group minerals with an afghanite-type framework. Full article

(This article belongs to the Special Issue Isomorphism and Solid Solutions of Minerals and Related Compounds)

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17 pages, 4954 KiB

Open AccessArticle

Textures and Chemical Compositions of Nb-Bearing Minerals and Nb Mineralization in the Shuangshan Nepheline Syenite Pluton, East Qinling, China

by Hong Wang, Yong Tang, Yu-Sheng Xu, Hui Zhang, Zheng-Hang Lv, Shan-Xian Qin and Ying-Wei Song

Minerals 2021, 11(11), 1163; https://doi.org/10.3390/min11111163 - 21 Oct 2021

Viewed by 1572

Abstract

The Shuangshan alkaline complex located in the Henan province of China is a newly discovered, potentially giant niobium (Nb) deposit. A variety of Nb-bearing minerals including pyrochlore, zircon, and titanite have been identified in this deposit. Distinct textural and chemical differences of pyrochlore [...] Read more.

The Shuangshan alkaline complex located in the Henan province of China is a newly discovered, potentially giant niobium (Nb) deposit. A variety of Nb-bearing minerals including pyrochlore, zircon, and titanite have been identified in this deposit. Distinct textural and chemical differences of pyrochlore and zircon indicate that both have different origins. The magmatic pyrochlore and zircon both have euhedral grains with small sizes. On the other hand, hydrothermal pyrochlore is mainly intergrown on the edge or inside of hydrothermal zircon in the form of an aggregate. Compared with magmatic pyrochlore, the contents of F, Ca, and Na in hydrothermal pyrochlore are obviously high. The texture and composition of hydrothermal pyrochlore and zircon indicate that Ca-bearing hydrothermal alteration resulted in the migration of Nb from Nb-bearing zircon and the reprecipitation of Nb to form aggregate pyrochlore. However, the quantitative calculation shows that the amount of Nb migrated from zircon is very small. Therefore, this study suggests that hydrothermal alteration plays a certain role in the redistribution of Nb, but the enrichment of Nb is limited. Full article

(This article belongs to the Special Issue Isomorphism and Solid Solutions of Minerals and Related Compounds)

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Review

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25 pages, 2885 KiB

Open AccessReview

Texture and Trace Element Geochemistry of Quartz: A Review

by Sajjad Ahmad Shah, Yongjun Shao, Yu Zhang, Hongtao Zhao and Lianjie Zhao

Minerals 2022, 12(8), 1042; https://doi.org/10.3390/min12081042 - 19 Aug 2022

Cited by 4 | Viewed by 4700

Abstract

Quartz is one of the most abundant minerals. Used in a variety of materials, it preserves geological history and reflects alteration conditions. Data were collected (>2400 data points) from more than 40 ore deposits to understand its internal texture and geochemistry. Cathodoluminescence imaging [...] Read more.

Quartz is one of the most abundant minerals. Used in a variety of materials, it preserves geological history and reflects alteration conditions. Data were collected (>2400 data points) from more than 40 ore deposits to understand its internal texture and geochemistry. Cathodoluminescence imaging is a technique for examining the internal texture of quartz that may reveal information about the crystal’s origin and evolution. The dominant trace elements in quartz lattice are Al, P, Li, Ti, Ge, K, and Na. These, combined with internal texture, can distinguish quartz from different origins and can differentiate between different types of ore deposits, as each type of ore deposit has its own unique CL characteristics. Therefore, Al did not correlate with cathodoluminescence (CL) in epithermal Au-Sb-Hg, Carlin-type Au, epithermal Ag, or shale-hosted Zn deposits. Epithermal base metal and porphyry-Cu-type deposits were intermediate, and Mississippi-Valley-type, epithermal Au-Ag, and porphyry Cu-Mo deposits were characterized for Al correlation with CL. Furthermore, Gigerwald, Rohdenhaus, and Westland deposits had Li/Al ratios less than one, suggesting that H (as hydroxyl substituting for oxygen) completed the charge. However, trace elements (i.e., Ge, Sb, Ti, and Al), sector zoning, and resorption surfaces were vital parameters to differentiate between magmatic and hydrothermal quartz. Additionally, titanium and aluminum were the most important trace elements. Their values could be used to differentiate between different quartz types. Among them, hydrothermal and pegmatitic quartz were characterized by lower temperatures and Ti concentrations. Rhyolitic quartz was characterized by the lowest Al, the highest temperatures, and lower Al/Ti ratios. Aluminum, Li, and H were most important in hydrothermal and metamorphic quartz, but magmatic quartz was generally enriched with Ti. Full article

(This article belongs to the Special Issue Isomorphism and Solid Solutions of Minerals and Related Compounds)

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