Journal articles: 'Spinelle'

1

Rheinboldt, Heinrich. "Konstitutionsformeln der Spinelle." Recueil des Travaux Chimiques des Pays-Bas 51, no. 4 (September 3, 2010): 356–60. http://dx.doi.org/10.1002/recl.19320510408.

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Verger, Louisiane, Olivier Dargaud, and Laurent Cormier. "Couleurs et émaux. Des décors de la Manufacture de Sèvres à la réactivité des pigments." Reflets de la physique, no. 63 (October 2019): 26–29. http://dx.doi.org/10.1051/refdp/201963026.

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Un décor de porcelaine est obtenu à l’aide de mélanges de pigments et de composants incolores qui, en se vitrifiant, fixent l’émail à la surface de l’objet et révèlent ainsi la couleu. Cet article s’intéresse à la stabilité d’un pigment de type spinelle au cours de la cuisson du décor. La caractérisation d’un grain de ce pigment par microscopie électronique, spectroscopie optique et absorption des rayons X, a permis de montrer que le changement de couleur parfois observé après cuisson résulte d’un enrichissement en chrome de la périphérie des grains de spinelle.

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Krutzsch, B., and S. Kemmler-Sack. "Spinelle im System Li1−zCuzRhRu1−xMnxO4." Journal of the Less Common Metals 132, no. 1 (April 1987): 37–42. http://dx.doi.org/10.1016/0022-5088(87)90171-8.

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CHEMLA, S., M. SGHYAR, M. RAFIQ, A. LARBOT, and L. COT. "Elaboration de membranes de spinelle de cobalt CoAlOO et de spinelle de manganèse MnAlOO pour l'ultrafiltration." Annales de Chimie Science des Matériaux 25, no. 7 (November 2000): 577–82. http://dx.doi.org/10.1016/s0151-9107(01)80012-x.

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Feltz, A., and A. Seidel. "Untersuchungen an elektronenleitenden Oxidsystemen. XXI. Stabile spinelle ZnzNiMn2?zO4 und Vergleich mit Spinellen MgzNiMn2?zO4." Zeitschrift f�r anorganische und allgemeine Chemie 608, no. 2 (February 1992): 166–72. http://dx.doi.org/10.1002/zaac.19926080225.

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6

CHASSAING, I., L. PRESMANES, Ph TAILHADES, A. ROUSSET, and P. MOLLARD. "Propriétés magnétiques de ferrites CoMnxFe2-xO4 (0ࣘxࣘ1) à structure spinelle." Le Journal de Physique IV 02, no. C3 (December 1992): C3–127—C3–131. http://dx.doi.org/10.1051/jp4:1992319.

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7

Kleinert, P. "Über die Darstellung kristallisierter Spinelle, besonders Ferrite, mit chemischen Transportreaktionen." Zeitschrift für Chemie 3, no. 9 (September 2, 2010): 353–54. http://dx.doi.org/10.1002/zfch.19630030914.

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8

Chassagneux, F., A. Rousset, and J. P. Redoules. "Elaboration et caracterisation de chromites de fer(III) a structure spinelle lacunaire." Journal of Solid State Chemistry 56, no. 1 (January 1985): 74–83. http://dx.doi.org/10.1016/0022-4596(85)90254-3.

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9

Schnick, Wolfgang. "Die ersten Nitrid-Spinelle – neue Synthesewege für binäre Nitride der 4. Hauptgruppe." Angewandte Chemie 111, no. 22 (November 15, 1999): 3511–12. http://dx.doi.org/10.1002/(sici)1521-3757(19991115)111:22<3511::aid-ange3511>3.0.co;2-j.

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10

Diouri, A., L. Ouichou, and A. Boukhari. "Interaction charge-briques réfractaires en magnésie spinelle dans un four industriel à ciment." Journal de Chimie Physique 88 (1991): 2341–46. http://dx.doi.org/10.1051/jcp/1991882341.

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11

OSTORÉRO, J., H. LE GALL, M. ESCORNE, F. SOULETTE, and A. PERCHERON-GUEGAN. "Nouvelle méthode de synthèse et propriétés de ferrite spinelle pour enregistrement magnétooptique réinscriptible." Le Journal de Physique IV 02, no. C3 (December 1992): C3–23—C3–28. http://dx.doi.org/10.1051/jp4:1992303.

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12

Putiš, Marián, Ondrej Nemec, Samir Ustalić, Elvir Babajić, Peter Ružička, Friedrich Koller, Sergii Kurylo, and Petar Katanić. "Mineralogical-Petrographical Record of Melt-Rock Interaction and P–T Estimates from the Ozren Massif Ophiolites (Bosnia and Herzegovina)." Minerals 12, no. 9 (August 30, 2022): 1108. http://dx.doi.org/10.3390/min12091108.

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The Dinaride Ophiolite Belt formed from the Jurassic part of the Neotethys. The investigated Ozren ophiolite complex in Bosnia and Herzegovina consists of peridotites, plagioclase peridotites, plagiogranites, troctolites and other gabbroic rocks, and fewer basalts. Lherzolites and harzburgites contain corroded ortho- and clinopyroxene1 porphyroclasts enclosed in the olivine matrix. The boundaries between olivine aggregates and pyroxene1 and spinel1 are infilled by medium-grained undeformed aggregates of clinopyroxene2, less orthopyroxene2, spinel2, and often clinopyroxene3-spinel3 symplectites. These textures indicate the final crystallization of peridotite in subsolidus conditions. Partial dissolution of deformed pyroxene1 porphyroclasts and coarse-grained spinel1 most likely occurred due to their reaction with the rest melt present in the grain boundaries. The Al decrease from pyroxene1 to pyroxene2 and 3, or the Cr decrease and Al increase from spinel1 to spinel2 and 3 is characteristic. Peridotites are associated with inferred remnants of a gabbro-dolerite layer, whereas basalts and radiolarites occur as rare dm-size fragments in an ophiolitic breccia. Troctolites display interstitial crystallization of plagioclase, clinopyroxene, less Na-Ti-rich amphiboles, and phlogopite in the olivine-spinel matrix, indicating the replacive character of impregnating melt within the dunite layers. Clinopyroxene-plagioclase-ilmenite-±amphibole gabbroic and fewer basaltic dykes in peridotites formed due to subridge extension, mantle thinning, and the deeper mantle melting. Iron-enriched olivines occur in the peridotite-dyke interfaces and troctolites. Hydrated ultramafics and mafics contain amphiboles, biotite, phlogopite, clinozoisite, epidote, and chlorite aggregates. Estimated magmatic to subsolidus T from peridotite two-pyroxene thermometry are 1000–850 °C, for the spinel facies. Ca-in-orthopyroxene1 thermometry provided T of 1028–1068 °C, and Ca-in-orthopyroxene2 thermometry gave 909–961 °C at estimated P of 1.1–0.9 GPa. However, the gabbroic dyke magmatic crystallization T was constrained to 1200–1100 °C at P of 0.45–0.15 GPa by single clinopyroxene thermobarometry. The obtained P–T conditions constrained the deeper mantle environment for the formation of peridotites than troctolites and crosscutting dykes. The ophiolitic thrust-sheet hanging wall conditions in an obduction-related accretionary wedge were estimated from amphibolites at 620 °C and 0.85 GPa by Ti-in-amphibole thermometry and amphibole-plagioclase thermobarometry. 300 °C and 0.5 GPa were determined from an exhumation shear zone using a combination of chlorite thermometry and Si-in-phengite barometry.

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13

Py, Francçoise, Josette Olivier-Fourcade, and Jean-Claude Jumas. "Caracte´risation du domaine de solution solide de structure spinelle dans le systeme In2S3Cu2SCuS." Journal of Solid State Chemistry 99, no. 2 (August 1992): 319–28. http://dx.doi.org/10.1016/0022-4596(92)90320-u.

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14

ALEKSEEV, Aleksandr Valer’evich, and Tat’yana Andreevna SHERENDO. "Composition, structure and magnetic properties of ore chrome spinels of the Klyuchevsky massif (Middle Urals)." NEWS of the Ural State Mining University 1, no. 1 (March 23, 2020): 73–85. http://dx.doi.org/10.21440/2307-2091-2020-1-73-85.

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The overall objective was to create a geological and geophysical field test site for chromite mineralization and detailed works in order to determine and test the main search criteria for disseminated mineralization. To create a field test site, an area was selected in the southern part of the Klyuchevsky massif characterized by abundant development of disseminated mineralization in the banded dunite-clinopyroxenite complex and strong processes of superimposed metamorphism. This paper gives a piece of research on the composition of chrome spinel from disseminated ores that underwent metamorphism of different stages. The composition of chrome spinelide, the evolution of its metamorphism and the related changes in its magnetic properties are examined in detail. It was established that all chrome spinels are of a high-chromium type, to one degree or another, they were subject to secondary changes, leading to the appearance of magnetic phases. The degree and nature of the change in chrome spinels in dunites directly depends on the degree of metamorphism of the rocks. The formation of the magnetic phase begins with the formation of nuclei consisting of single magnetic dipoles, groups of 2-3 dipoles or chains of magnetic dipoles, which was first discovered by us in chrome spinel grains. Then there is an increase in the number of such phases, the appearance of optically diagnosed secondary changes in chrome spinelide. A comparison of the degree of variation of chrome spinel and its reflection in the pattern of recorded anomalies of geomagnetic fields allows us to identify some criteria for the search for disseminated chromite ores of this type.

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15

Gerardin, R., A. Alebouyeh, J. F. Brice, O. Evrard, and J. P. Sanchez. "Distribution cationique dans les ferrites d'indium de type spinelle InMFeO4 (M = Ni, Mn, Co, Mg)." Journal of Solid State Chemistry 76, no. 2 (October 1988): 398–406. http://dx.doi.org/10.1016/0022-4596(88)90234-4.

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16

Cabanes, Nelly, and Jean-Claude Mercier. "Chimie des phases minérales et conditions d'équilibre des enclaves de lherzolite à spinelle de Montferrier (Hérault, France)." Bulletin de Minéralogie 111, no. 1 (1988): 65–77. http://dx.doi.org/10.3406/bulmi.1988.8071.

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17

Masson, O., Z. Oudjedi, A. Fillon, R. Guinebretière, and A. Dauger. "Détermination des microdéformations dans des matériaux composites spinelle-zircone par diffractométrie X haute résolution en réflexion asymétrique." Le Journal de Physique IV 08, PR5 (October 1998): Pr5–437—Pr5–443. http://dx.doi.org/10.1051/jp4:1998555.

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18

Gillot, B., and A. Rousset. "Sur la relation entre la distribution des cations dans la structure spinelle et leur réactivité dans l'oxygène." Journal of Solid State Chemistry 65, no. 3 (December 1986): 322–30. http://dx.doi.org/10.1016/0022-4596(86)90104-0.

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19

Largeteau, A., J. M. Reau, and J. Ravez. "Dispersions diélectrique et d'impédance et énergies d'activation de céramiques á couches d'arrêt de type spinelle non stoechiométrique." physica status solidi (a) 121, no. 2 (October 16, 1990): 627–34. http://dx.doi.org/10.1002/pssa.2211210235.

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20

Xu, Qian, Bo Xu, Yujie Gao, and Siying Li. "Characterization of Red, Pink, Orange, and Purple Gem-Quality Spinel from Four Important Areas." Crystals 14, no. 1 (December 29, 2023): 50. http://dx.doi.org/10.3390/cryst14010050.

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Spinel is a precious stone with a long history. In ancient societies spinel was considered to be an imitation of ruby. With the depletion of ruby mineral resources, gem—grade spinel has attracted more and more attention from consumers. In the last decade, as the popularity of spinel in the global colored gem market continues to rise, plenty of domestic and foreign jewelry brands have launched spinel based jewelry. This study takes spinels from Burma, Vietnam, Sri Lanka, and Tanzania as its research objects and performs a series of tests to obtain their gemological characteristics, spectral characteristics, and chemical composition, with the aim of comparing the differences between spinels with different colors from different areas and exploring the chromogenic mechanism of spinels. Only Burmese red spinels have a typical Cr spectrum. The types of inclusions and the contents of trace elements are the main differences between spinels from the four areas. Burmese spinel is characterized by an octahedral negative crystal filled with dolomite or a mixture of dolomite and calcite. Magnesite is present in Sri Lankan spinels, and dolomite is present in Tanzanian spinel. Dislocation systems and the presence of titanite and talc inclusions are strongly indicative features of Vietnamese spinel. Sri Lankan spinel is characterized by abundant gas–liquid inclusions, such as the beaded healing fissure. The trace element contents of the four areas are different. Burmese spinel is poor in Fe and Zn (Fe: 135.68–3925 ppm; Zn: 338.58–1312 ppm), while Burmese red spinel is rich in Cr (up to 7387 ppm). Vietnamese spinel is rich in Fe (3669.63–19,425 ppm) and poor in Ti content (<89 ppm), while Tanzanian spinel is rich in Zn (5129.96–7008 ppm). High content of Cr + V can lead to the red color in spinel, and the contents of Cr and V change obviously with color. Spinels appear red when Cr content is higher than V, while spinels appear orange when V content is higher than Cr. The red, pink, and orange spinels are colored by Cr3+ and V3+, showing a wide absorption band centered at 400 nm and 550 nm. Fe plays a dominant role in purple spinels. The purple spinel is colored by Fe3+ and Fe2+.

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21

Riedel, E., D. Prick, and E. Wolska. "Mößbauer-Untersuchung ferrimagnetischer Spinelle des Systems CdϰNi1-ϰFe2O4 / Mößbauer Investigation of Ferrimagnetic Spineis in the System CdϰNi1-ϰFe2O4." Zeitschrift für Naturforschung B 49, no. 8 (August 1, 1994): 1067–70. http://dx.doi.org/10.1515/znb-1994-0810.

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Room temperature Mößbauer spectra of ferrimagnetic spinels in the system Cdϰ2+Fe1-ϰ3+[Ni1-ϰ2+Fe1-ϰ3+]O4 have been interpreted using the polyhedron model which is based on six different environments at the A-site for the B-site Fe3+-ions. To each environment belongs one sextet with a characteristic magnetic splitting. An additional sextet is due to Fe3+-ions at the A-site.

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22

Feltz, A., J. T�pfer, and B. Neidnicht. "Untersuchungen an elektronenleitenden Oxidsystemen. XXIII. Struktur und Eigenschaften stabiler Spinelle in den Reihen MzNiMn2?ZO4 (M=Li, Fe)." Zeitschrift f�r anorganische und allgemeine Chemie 619, no. 1 (January 1993): 39–46. http://dx.doi.org/10.1002/zaac.19936190108.

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23

Arai, Shoji. "Chemistry of chromian spinel in volcanic rocks as a potential guide to magma chemistry." Mineralogical Magazine 56, no. 383 (June 1992): 173–84. http://dx.doi.org/10.1180/minmag.1992.056.383.04.

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AbstractChromian spinel in volcanic rocks is a potential discriminant for magma chemistry. The TiO2 content of spinel, compared at similar Fe3+/(Cr + Al + Fe3+) ratios, can distinguish island arc basalts from intraplate basalts. MORB spinels are low in this ratio and are intermediate for the TiO2 level at comparable Fe3+ ratios. Spinels from back-arc basin basalts, although similar in TiO2/Fe3+ ratio, are more enriched in Fe3+ than the MORB spinels. Spinels in the oceanic plateau basalts are distinctly lower in TiO2 than other intraplate basalt spinels and even slightly lower in TiO2 than the MORB spinels. The data were successfully applied to estimate the kind of the magma from which spinelbearing cumulates, especially dunites, were formed. Original magma chemistry of altered or metamorphosed volcanics in which spinels survive can also be estimated by the chemistry of relict spinel alone. It is possible to estimate the magma type of source volcanics for detrital spinel particles of volcanic derivation.

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IBHI, A., H. NACHIT, D. KHATIB, E. ABIA, and J. HERNANDEZ. "La loi de fick adaptee a la diffusion cationique dans un solide semi-infini : Application aux megacristaux de spinelle." Annales de Chimie Science des Mat�riaux 24, no. 2 (February 1999): 117–24. http://dx.doi.org/10.1016/s0151-9107(99)80056-7.

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25

Kubovics, Imre, Zsolt Bendő, Kamilla Gál-Sólymos, Zuárd Ditrói-Puskás, Dóra Georgina Miklós, and Balázs Ivanics. "A kabai meteorit újravizsgálatának fontosabb eredményei." Földtani Közlöny 148, no. 3 (August 31, 2018): 205. http://dx.doi.org/10.23928/foldt.kozl.2018.148.3.205.

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A kabai meteoritban többféle eredetű és összetételű hőálló (refraktorikus) ásvány, hőállóásvány-társulás mutatható ki. Legtöbbet és legjellegzetesebbeket a fehérzárványhalmazok, továbbá a kerekded–ovális kondrumszerű képződmények, valamint a 100–200 μm átmérőjű „kondrumok” tartalmaznak. A meteorit felszínén is látható – általában 10–18 mm hosszú – sárgásfehér „zárványokat” a mikroszkópi vizsgálatok szerint többnyire teljesen szabálytalan alakú, „szaggatott” szerkezetű, szemcsés halmazok alkotják. Helyenként egymás közvetlen közelében több különböző méretű halmazból álló csoport alakult ki, valószínűleg egy nagyobb darab széttöredezése eredményeképpen. A halmazok mozaikos szerkezete is ezzel magyarázható. Az uralkodóan 100–400 μm méretű, gyakran különböző összetételű, részben alapanyagot is tartalmazó szemcsék általában bonyolult zónás szerkezetűek. Leggyakoribb, illetve legnagyobb mennyiségű összetevője a magot alkotó, de kisebb mennyiségben rendszerint a többi övben is megjelenő közönséges spinell. A következő öveket részben gehlenit, de uralkodó mennyiségben, titánban és alumíniumban gazdag monoklin piroxének alkotják. Egyes szemcsék körül záró övként a forsterit is megjelenik. A kerekded–ovális megjelenésű, kondrumszerű képződmények, valamint a kis méretű kondrumok az előzőekkel megközelítőleg, illetve részben azonos ásványi összetételűek, az alkotók mennyiségi arányában, valamint a képződési sorrendben azonban jelentős különbségek mutatkoznak. Az uralkodó magalkotó fázisok általában változó mennyiségű zárványt tartalmaznak. Például a gehlenitben rendszerint kevés perovszkit és részben spinell, a közönséges spinellben pedig többnyire sok perovszkit mutatható ki. Külön kiemelkedő a kerek „felhőszerű” halmaz magjának túlnyomó részét alkotó magnéziumtartalmú gehlenit nagy mennyiségű, mégpedig 72% platinát, továbbá — többek között — irídiumot és kevés hafniumot is tartalmazó „zárványa”. A kerekded–ovális képződményeken belül az alakzat, a szerkezet, valamint a jellemző ásványok alapján gehlenitet, közönséges spinellt, valamint normatív hercinitet és korundot tartalmazó változatot különböztethetünk meg. A jellemző uralkodó ásványok rendszerint az adott változat magját alkotják, és általában jelentős mennyiségű „zárványt” — főleg kerekded perovszkitot tartalmaznak. A mag körüli övezetet főleg spinell és monoklin piroxének alkotják. Egyes változatokban azonban az 5–7% Na2O-t tartalmazó — esetenként önálló övet alkotó — amorf anyag („mezosztázis”) is jelentős mennyiséget képvisel. Ez az öv valószínűleg a Mokoia-meteoritban kimutatott (MACPHERSON et al. 1983) filloszilikátokhoz hasonló összetételű (normatív) rétegszilikátokat is tartalmaz.

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Dautria, Jean-Marie, and Michel Girod. "Les enclaves de lherzolite à spinelle et plagioclase du Volcan de Dibi (Adamaoua, Cameroun) : des témoins d'un manteau supérieur anormal." Bulletin de Minéralogie 109, no. 3 (1986): 275–88. http://dx.doi.org/10.3406/bulmi.1986.7934.

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Saveliev, D. E. "Morphological and Compositional Features of Chromian Spinel from Mantle Ultramafic Rocks of The Nurali Massif (South Urals)." МИНЕРАЛОГИЯ (MINERALOGY) 5 (December 27, 2019): 3–18. http://dx.doi.org/10.35597/2313-545x-2019-5-4-1.

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Accessory chromian spinels of lherzolites and dunites from a mantle section of the Nurali ophiolite massif are described in the paper. Lherzolites typically host anhedral chromian spinel grains associated with olivine, pyroxenes and plagioclase. The compositions of silicates and chromian spinels are typical of those from ophiolite mantle sections. Olivine and orthopyroxene are characterized by high Mg content (forsterite and enstatite); clinopyroxene is diopside. The compositions of chromian spinel on the Al–Cr–Fe+3 plot occur close to the Al–Cr side. The #Cr and #Mg values of chromian spinels increase from lherzolites to dunites. Both vermicular spinels trapping olivine and orthopyroxene fragments (type I) and symplectite-like intergrowths of chromian spinel and plagioclase (type II) are most genetically interesting. Type I formed during synkinematic growth in deformed silicate matrix. Type II possibly formed as a result of decompression breakdown of a high-P mineral phase enriched in Cr, Al and Ca (a knorringite-type garnet?). In dunites, numerous tiny chromian spinel rods (type IV) in plastic deformed olivine are observed along with typical euhedral chromian spinel (type III) with inclusions of olivine and pargasite. Latter ones locally occur closely to fne pargasite grains. The formation of chromian spinel rods is explained as a result deformation-induced segregation of trace elements on the structural defects of the olivine lattice. Figures 7. Tables 4. References 48.

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Agnoli, Fabrice, Boris Albouy, Philippe Tailhades, and Abel Rousset. "Manganites de fer de structure spinelle déformée à très fort champ coercitif. Exemple de l'oxyde lacunaire à valence mixte Mn1,7Fe1,3O4+δ." Comptes Rendus de l'Académie des Sciences - Series IIC - Chemistry 2, no. 9-10 (September 1999): 525–30. http://dx.doi.org/10.1016/s1387-1609(00)86438-5.

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Pownceby, M., and P. Bourne. "Detrital chrome-spinel grains in heavy-mineral sand deposits from southeast Africa." Mineralogical Magazine 70, no. 1 (February 2006): 51–64. http://dx.doi.org/10.1180/0026461067010312.

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AbstractDetrital chrome-spinels are contaminant grains within ilmenite concentrates produced from heavy-mineral deposits along the coast of southeast Africa. The presence of even minor levels of chromia in the predominantly ilmenite-rich concentrates, downgrades their market value as potential feedstocks for the production of titania pigment. An understanding of their composition can assist in their removal from the ilmenite concentrates.Compositions from a database of close to 900 chrome-spinel analyses shows the major element components and their ranges (in wt.%) are: Cr: 0.4-45.3, Al: 0.0-31.0, Fe: 8.5-69.6 and Mg: 0.0-12.2. Minor components include Ti: 0.1-11.4 and Zn: 0.0-13.7.The chrome-spinel data fall into two compositionally distinct groups. The first group of spinels is dominated by a strong trend reflecting the mutual substitution between Al3+ and Cr3+ in the spinel structure. The second group of spinels is characterized by compositions containing abundant Fe3O4 magnetite component. The clear division between chrome-spinel compositional types indicates the grains are derived from at least two chemically dissimilar provenances.The compositional differences between the chrome-spinel groups has a positive impact on subsequent ilmenite upgrading treatments as the spinels which contain the highest magnetite component are easily removed via low-intensity magnetic separation procedures.

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Kepezhinskas, Pavel K., Rex N. Taylor, and Hisao Tanaka. "Geochemistry of plutonic spinels from the North Kamchatka Arc: comparisons with spinels from other tectonic settings." Mineralogical Magazine 57, no. 389 (December 1993): 575–89. http://dx.doi.org/10.1180/minmag.1993.057.389.02.

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AbstractUltramafic to marie plutons in the Olyutor Range, North Kamchatka, represent the magmatic roots of a late Eocene arc, related to the westward subduction of the Komandorsky Basin beneath the Asian continental margin. Olyutor Range plutons are concentrically zoned with cumulate dunite cores mantled by a wehrlite-pyroxenite transitional zone and, in turn, by a narrow gabbroic rim.Spinel is a common accessory mineral in these arc plutonics, and we present analyses of spinels from a range of lithologies. A continuous compositional trend is observed from Cr-spinel in the ultramafics to Cr-rich magnetite in marginal gabbros. Complex chemical zoning patterns within individual spinel grains suggest an interplay between fO2, fractionation, volatile content and subsequent sub-solidus reequilibration of spinel with co-existing silicates (mainly olivine).In general, the spinels from magmatic arc environments are characterised by high total Fe and high Fe3+ contents compared to MORB and boninitic spinels and higher Cr-values relative to oceanic basin spinels. These differences imply a high oxygen fugacity during arc petrogenesis. Differences are also observed between plutonic spinels from arcs and low-Ti supra-subduction zone ophiolites. Low-Ti ophiolitic spinels are generally poorer in iron and richer in Cr, and hence are similar in composition and perhaps tectonic setting to fore-arc boninitic spinels.

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Pokhilenko. "Formation Sequence of Different Spinel Species in Megacrystalline Peridotites of the Udachnaya-East Kimberlite Pipe (Yakutia): Evidence for the Metasomatism of Depleted Mantle." Minerals 9, no. 10 (October 3, 2019): 607. http://dx.doi.org/10.3390/min9100607.

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The large compositional variations in spinels from extremely depleted, megacrystalline harzburgite–dunites in the Udachnaya-East kimberlite pipe, Yakutia, apparently reflect multistage metasomatism. Changes in the redox regime are reflected in the compositions of different parts of mineral grains. From most reduced to most oxidized, spinel compositions divide into: (1) primary (rock-forming) Cr-spinel and spinel from the central parts of sulfide grains, (2) spinel from microcracks in olivine, (3) spinel in kelyphitic rim around garnet between garnet and olivine (Rim1 and Rim2 spinel), and (4) spinel in transformed kelyphitic rim around garnet between garnet and kimberlite (Rim3 spinel). P-T conditions for the vast majority of samples, calculated using the composition of primary Cr-spinel, fall in the diamond stability field. A change in the composition of spinels of different generations occurs along the sides of the classical triangle of spinel compositions Al–Сr–Fe3+: (1) Rim2 to Rim1 spinel—Al–Cr trend, (2) primary Cr-spinel to magnetite rim in the edge—Cr–Fe3+ (kimberlite) trend, (3) replacing Rim1 to Rim3—Al–Fe3+ trend.

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32

Zhang, Zhibin, Fei Huang, Yongli Li, Kaijun Liu, and Fude Zhao. "Nano-Micron Exsolved Spinels in Titanomagnetite and Their Implications for the Formation of the Panzhihua Fe–Ti–V Oxide Deposit, Southwest China." Journal of Nanoscience and Nanotechnology 21, no. 1 (January 1, 2021): 326–42. http://dx.doi.org/10.1166/jnn.2021.18448.

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The nano-micron exsolved spinels with various mineralogical characteristics in titanomagnetite from Fe–Ti oxide gabbros in the Panzhihua Fe–Ti–V oxide deposit, SW China, have been studied by field emission scanning electron microscopy (FE-SEM) and electron probe microanalysis (EPMA) based on comparisons of physical and chemical conditions at different stratigraphic heights to investigate the compositional inheritance between titanomagnetite and exsolved spinel and further explore the relationship between the morphology and growth of exsolved spinels. Restored chemical data for titanomagnetite combined with evidence from petrography and whole-rock geochemistry imply fractional crystallization of the Panzhihua Fe–Ti–V oxide deposit, where the titanomagnetite of thick massive oxides at the bottom of the No. VIII orebody represents the early crystallizing phase characterized by high temperature and oxygen fugacity. The chemical variation in the exsolved spinel, which has the same trend as the restored composition of titanomagnetite, represents inheritance from the parent rock within the Panzhihua deposit. Exsolved spinel continuously adjusts morphology and grain size to decrease the total energy of the manganate-spinel system from fine-grained spinels parallel to the {100} plane of titanomagnetite to spinels with complex stellate morphology to bulky granular spinels with high degrees of idiomorphism. The unusual multiple magma replenishment during the mineralizing process and at different stratigraphic heights in the Panzhihua intrusion had an important influence on the thermal evolution history of the orebody, resulting in the identifiable spatial distribution patterns of spinel morphology and grain size. Using spinel exsolution as a discriminator for the provenance of magmatic ore deposits may provide intuitive and easy mineralogical evidence to qualitatively discuss the evolution of the metallogenetic environment and the ore-forming conditions for similar large mafic intrusions.

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Bouloton, Jacky, Philippe Goncalves, and Christian Pin. "Le pointement de péridotite à grenat-spinelle de La Croix-Valmer (Maures centrales): un cumulat d'affinité océanique impliqué dans la subduction éohercynienne ?" Comptes Rendus de l'Académie des Sciences - Series IIA - Earth and Planetary Science 326, no. 7 (April 1998): 473–77. http://dx.doi.org/10.1016/s1251-8050(98)80073-6.

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34

ASWAD, KHALID J. A., NABAZ R. H. AZIZ, and HEMIN A. KOYI. "Cr-spinel compositions in serpentinites and their implications for the petrotectonic history of the Zagros Suture Zone, Kurdistan Region, Iraq." Geological Magazine 148, no. 5-6 (July 11, 2011): 802–18. http://dx.doi.org/10.1017/s0016756811000422.

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AbstractAccessory chrome spinels are scattered throughout the serpentinite masses in two allochthonous thrust sheets belonging to the Penjween–Walash sub-zone of the northwestern Zagros Suture Zone in Kurdistan. Based on field evidence, the serpentinites are divided into two groups: (1) highly sheared serpentinites (110–80 Ma), which occupy the lower contact of the ophiolitic massifs of the Upper Allochthonous sheet (Albian–Cenomanian age), and (2) ophiolitic mélange serpentinites of mixed ages (150 and 200 Ma) occurring along thrust faults on the base of the volcano-sedimentary segment (42–32 Ma) of the Lower Allochthonous sheet. The Cr-spinels of both groups show a wide range of YCr (Cr/(Cr + Al) atomic ratio) from 0.37 to 1.0, while the XMg (Mg/(Mg + Fe2+) atomic ratio) ranges from 0.0 to 0.75. Based on the Cr-spinel compositions of the entire dataset and in conjunction with back-scattered electron imaging, from core to rim, three spinel stages have been recognized: the residual mantle stage, a Cr-rich stage and a third stage showing a very narrow magnetite rim. These three stages are represented by primary Cr-spinel, pre-serpentinization metamorphosed spinel and syn- or post-serpentinization spinel, respectively. The chemical characteristics of primary (first-stage) Cr-spinels of both serpentinite groups indicate a tectonic affinity within a fore-arc setting of peridotite protoliths. The second stage indicates that Cr-spinels have undergone subsolidus re-equilibration as a result of solid–solid reaction during pre-serpentinization cooling of the host rock. Here the primary Cr-spinel compositions have been partly or completely obscured by metamorphism. During the third stage, the Cr-spinels have undergone solid–fluid re-equilibration during syn- or post-serpentinization processes. Both the second and third stages point to diachronous metamorphic paths resulting from continuous tectonic evolution influenced by either slow or fast uplift of mantle protoliths. In the fast metamorphic paths, the primary chrome spinels are flanked by a very narrow magnetite rim. The presence of two groups of distally separated serpentinites with different emplacement ages and fore-arc tectonic affinity could indicate that the closure of the Tethys Ocean culminated in two fortuitous subduction processes.

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35

Mekhonoshin, Aleksey S., Tatiana B. Kolotilina, Artemy A. Doroshkov, and Evgeniya E. Pikiner. "Compositional Variations of Cr-Spinel in High-Mg Intrusions of the Primorsky Ridge (Western Baikal Region, Russia)." Minerals 10, no. 7 (July 7, 2020): 608. http://dx.doi.org/10.3390/min10070608.

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Composition variations of Cr-spinel in high-Mg rocks of the Primorsky Ridge (Western Baikal region, Russia) are reported here. A specific feature of Cr-spinels in ultramafic rocks of the Primorsky Ridge is their noticeably high Ti content (up to 6.5 wt.%) compared to spinels in mantle peridotites. The presence of high TiO2 content in Cr-spinels enclosed in olivine crystals may be a clear indication of the primary magmatic nature of Ti enrichment. Two types of Cr-spinel were identified in ultramafic rocks from all intrusions. Cr-spinels of Type I are enclosed in the inner part of olivine crystals and are homogeneous Al-rich chromites and Fe2+-rich chromites. They are characterized by variable content of TiO2 (1.0–5.3 wt.%), moderately high Cr# (0.7–0.83), and low Fe3+# (0.20–0.34). Cr-spinels of type II occur in the interstitial space and occur as homogeneous and zoned grains with Al-rich chromite and Fe2+-rich chromite cores. Al-rich chromite cores have a composition similar to that of the Cr-spinel enclosed in olivine crystals. Fe2+-rich chromite cores have relatively high MgO (3.8–6.2 wt.%), Al2O3 (8–9 wt.%), and TiO2 (2.6–2.8 wt.%) content, low MnO (0.34–0.52 wt.%) content, and a low Fe3+# (0.25–0.27) ratio.

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36

Zhang, Lei, Kui He, and Qingfeng Guo. "Spectroscopic Characteristics and Coloring Mechanisms of Different Colored Spinels from Myanmar." Crystals 13, no. 4 (March 28, 2023): 575. http://dx.doi.org/10.3390/cryst13040575.

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Spinel is a common gemstone that has attracted the attention of gemologists worldwide because of its high refractive index, rich colors and brilliant hues. Myanmar is an important source of spinel. The present paper provides a systematic characterization of the gemological features of different color spinels from Myanmar, with a discussion and analysis of their color causes. The results show that complete octahedral crystal forms can be seen in Myanmar spinel, with the appearance of dissolution, growth motifs and cross-growth of crystals visible on the crystal surfaces. The XRF results show that the Myanmar red and orange spinel samples contain high levels of Cr, with the magenta sample having significant levels of Cr and the orange sample having more V. The blue and purple samples have high levels of Fe. The peaks of the infrared spectrum mainly appear around 841 cm−1, 690 cm−1 and 532 cm−1. Raman spectra have peaks mainly around 310 cm−1, 405 cm−1, 663 cm−1 and 764 cm−1. According to the UV-Vis spectrum, the color of Myanmar red and orange spinels is mainly due to Cr3+ and V3+. When the Cr3+ content is higher than the V3+ content, the spinels show a red hue; when the V3+ content is higher than Cr3+, the spinels have an orange hue. Blue color is due to the charge transfer between Fe2+ and Fe3+. The research in this paper has enriched the gemological characteristics of Myanmar spinel and can provide a theoretical basis for its investigation, marketability, design and utilization.

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37

Zhao, Yi, Bo Xu, Zheyi Zhao, Qian Xu, and Zhaoyi Li. "Gemological and Chemical Characterization of Varicolored Gem-Grade Spinel from Mogok, Myanmar." Crystals 13, no. 3 (March 4, 2023): 447. http://dx.doi.org/10.3390/cryst13030447.

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Spinel is a precious gem with a long history, but people are far less familiar with it. Previous studies on Mogok spinel from Myanmar focused on inclusion analysis, chromogenic mechanism with a single-color gemstone and heat treatment, whereas systematic studies on varicolored gem-grade spinel are lacking. In this study, the gemological and geochemical analysis of four colors of spinel samples from Mogok were carried out for basic gemology, inclusion morphology and identification, spectroscopy and geochemistry. The aim was to explore the occupation of elements of spinels in the crystal structure, as well as the chromogenic mechanism of varicolored spinels and the geological and geodynamic conditions of the formation. Mogok spinel samples are characterized by octahedral negative crystals filled with calcite and chondrodite inclusions, indicating that they are derived from a marble metamorphic-type deposit. The spinel samples of four colors are magnesia–alumina spinel (MgAl2O4). The contents of V and Cr in Mogok spinel are generally high, with a significant high content of Zn being the most characteristic, and trace elements vary greatly. The infrared spectra of spinel samples in different colors are basically similar. According to the UV–Vis spectrum, pink and red samples are mainly colored by Cr and/or V, whereas orange samples are mainly colored by V. Two wide absorption bands in the range 300~600 nm are mainly attributed to the spin-allowed transition and spin-forbidden transition of Cr3+ and/or V3+. The purple samples are mainly colored by Fe and the UV–Vis spectrum is mainly attributed to the spin-forbidden transition of TFe2+. This study is a favorable supplement to the research on Mogok spinels of various colors from multiple perspectives.

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38

Ahmad, S., M. A. Rhamdhani, M. I. Pownceby, and W. J. Bruckard. "Exploratory Study of Separation of Sulphidised Chrome Spinels from Reduced Ilmenite." Minerals 12, no. 10 (September 30, 2022): 1252. http://dx.doi.org/10.3390/min12101252.

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The removal of chromium-containing impurities, such as chrome spinel (ZCr2O4 where Z = Fe, Mg, Mn) from ilmenite (FeTiO3) concentrates through selective sulphidation, has been investigated by the authors. Laboratory experimental studies using sulphur added to ilmenite concentrates under Becher-type reduction conditions showed it is possible to selectively sulphidise chrome spinels from different ilmenite deposits. In this paper, processes to remove the sulphidised chrome spinels from the bulk ilmenite concentrates were investigated using flotation and magnetic separation techniques. Clustering or fusing of the reduced ilmenite (RI) and sulphidised chrome spinel grains was found to have a detrimental effect on flotation performance and made it difficult to have clear separation. A light wet grind was effective for breaking the clustering, but it caused the sulphide rim to spall off from chrome spinel surfaces, which reduces flotation efficiency. The preliminary results obtained after a magnetic separation (0.7 A) of a demetallised sulphidised RI sample show that the sulphidised chrome spinels preferentially report to the magnetic fraction. Additional magnetic separation of the non-magnetic fraction at a lower current (0.3 A) improved the recovery of sulphidised chrome spinels. The demetallisation process followed by a magnetic separation provided insights into a potential route for the removal of chrome spinels from reduced ilmenite concentrates. These two steps simulate the aeration stage of the Becher process. Further studies are required to optimise the process parameters.

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39

Abbou-Kebir, Khadidja, Shoji Arai, Ahmed Hassan Ahmed, and Georges Ceuleneer. "Spinel-free and spinel-poor dunite veins crosscutting the Wadi Rajmi ophiolite chromitite (northern Oman ophiolite)." Bulletin de la Société Géologique de France 184, no. 3 (March 1, 2013): 261–66. http://dx.doi.org/10.2113/gssgfbull.184.3.261.

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Abstract Peculiar dunitic veins almost or totally free of spinels crosscut a podiform chromitite ore body in the Wadi Rajmi, northern Oman ophiolite. They probably originated from a komatiitic melt which was oversaturated in Fo≤94 olivines and which evolved to precipitate simultaneously both chromian spinels, with Cr# ranging from 0.6 to 0.8, and Fo91-93 olivines. The absence or the low modal amounts of spinels are possibly governed by a Cr-undersaturation state of the involved melt which crystallized under relatively low cooling rates to generate the spinel-free and the spinel-poor dunites. A shallow and highly depleted mantle source for this komatiitic melt was envisaged during a converging tectonic regime, initiated earlier in the dynamic history of the Oman ophiolite.

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40

Zhao, Longpei, Geng Li, and Liqun Weng. "Gemological and Spectroscopic Characteristics of “Jedi” Spinel from Man Sin, Myanmar." Minerals 12, no. 11 (October 26, 2022): 1359. http://dx.doi.org/10.3390/min12111359.

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The price of spinel has sharply risen in recent years, and its market acceptance is extending. Among the many sources of spinel, Man Sin in Myanmar is the most famous for its bright neon pinkish red to reddish pink color, named “Jedi” spinel commercially. In this paper, spinel samples with the bright neon pinkish red to reddish pink from Man Sin in Myanmar were studied non-destructively with X-ray fluorescence spectrometer (EDXRF), Fourier transform infrared spectrometer (FTIR), fluorescence spectroscopy, a UV-Vis spectrophotometer and Raman spectroscopy. The results show that the samples from Man Sin in Myanmar are the magnesia-alumina spinels. The high content of the red-chromogenic element Cr, an intermediate content of V and Zn, and a low content of the chromogenic element Fe may be responsible for the distinctive neon color of the spinel samples. The presence of Ti may also serve as a basis for the identification of its origin in Man Sin in Myanmar. The fluorescence spectrum analysis of spinels shows them to have multiple excitation peaks in the region 600–800 nm, which are caused by the jump of Cr3+ between the 2E→4A2 inter-energy band lattice. The amount of Zn affects the fluorescence spectrum intensity of spinels. The higher the Zn content, the stronger the fluorescence intensity. The spinel structure is uncomplicated and four more obvious absorption peaks appear in the IR spectrum, and the direction of the absorption peaks is shifted if a homogeneous substitution of the AB2O4 structure occurs; the Raman spectra of spinel samples have four vibrational peaks at 100–2000 cm−1, 310 cm−1, 407 cm−1, 665 cm−1 and 763 cm−1, which has spinel species-identification significance.

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41

Gilewicz-Wolter, Jolanta, Zbigniew Żurek, J. Dudala, Jerzy Lis, Martah Homa, and Marcin Wolter. "Diffusion Rates of⁵¹Cr,⁵⁴Mn and ⁵⁹Fe in MnCr₂O₄ and FeCr₂O₄ Spinels." Advances in Science and Technology 46 (October 2006): 27–31. http://dx.doi.org/10.4028/www.scientific.net/ast.46.27.

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As the result of oxidation of Cr-Mn steels in SO2 the three layer scale is formed. The intermediate layer of this scale is composed mainly of MnCr2O4 spinel whereas FeCr2O4 spinel is present in small amount. MnO dominates in the outer layer. The inner, very thin scale layer contains oxides/sulfides mixture. The aim of this study was to examine self-diffusion processes in both spinels by multitracer method of diffusion measurements to know which of the transport processes during oxidation is the smallest one and deciding on the corrosion rate. In diffusion experiments the radioisotopes 54Mn, 51Cr and 59Fe were used. The serial sectioning method was applied to simultaneous evaluation of diffusion rates of chromium, manganese and iron in both spinels at 1073 K and 1173 K under the pressure of 105 Pa in SO2 containing 10 Pa O2. These spinels were obtained by modified sol-gel method from nitrates. Structures of the spinels were examined by X-ray spectrometry. It was found, that the diffusion rates of metals are higher in MnCr2O4 spinel. Moreover the dominant mechanism of manganese transport (the highest one) in studied samples is the volume diffusion while chromium and iron are transported mainly through the high diffusivity paths.

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42

Heneralova, Larysa, Oleg Hnylko, Nataliya Bilyk, and Volodimir Stepanov. "Evolution of mesozoic peridotites of the coal ophiolite complex (marmara rock zone, inner Ukrainian Carpathians)." Visnyk of the Lviv University. Geology Series 35, no. 35 (2021): 53–71. http://dx.doi.org/10.30970/vgl.35.06.

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The paper presents the results of the study of peridotites of the Ugolka ophiolite complex of the Inner Ukrainian Carpathians. The work is based on the data of prior research and original materials of geological observations from the middle course of the Tereblya River, and on new laboratory analyzes of peridotites. Middle Triassic – Lower Cretaceous (?) Peridotites of the Ugolka ophiolite complex form olistolites in the Lower Cretaceous olistostrome-conglomerates of Soimul formation. Petrographic data make it possible to classify disparate olistolites of the ophiolite complex, and peridotites in particular, into two types of ophiolite associations, which were formed in different conditions according to indicator minerals (including spinelides). Results of the study of spinelites form two groups that correlate with two equilibrium mineral associations: first – olivine + spinel + orthorhombic pyroxene + monoclinic pyroxene; and second – amphibole + talc. Larger isometric or xenomorphic individuals of chromium spinels are found in harzburgites and lherzolites. Smaller chromium spinel individuals form elongated and elliptical grains, stretched along the structure of the rock, and are found in the interstices of pyroxene and olivine crystals. X-ray microprobe analysis revealed that the composition of chromium spinel grains of the first group contains more magnesium and less chromium. chromium spinels of the second group are smaller, and contain less magnesium and more chromium. On the binary diagram Cr#–Mg# chromium spinels from the peridotites of the Ugolka complex are concentrated in two areas: abyssal peridotites and suprasubduction peridotites. chromium spinel grains from the first group crystallized at a low degree of partial melting (Dmelt up to 14 %), which is typical for abyssal peridotites. chromium spinels of the second group crystallized at a higher degree of melting (Dmelt up to 30 %), which is characteristic of peridotites of suprasubduction zones. On the correlation diagram of the average chromium spinel and the total spreading speed, the chromium spinel compositions of the first group of the Ugolka complex corresponds to the peridotites of ultra-slow spreading zones. Small grains from the second group of chromium spinels of the Ugolka complex are associated with peridotites of fast spreading zones. The temperature of metamorphism of rocks of the first mineral association is estimated by spinel and olivine-spinel geothermometers, and is contained within range of 900–1 290 ºС, at pressure aprox. 15 kbar. The temperature of metamorphism of rocks forming the second mineral association, I estimated at 430–450 °C, at pressure of 4.0–4.5 kbar. The study of peridotites of the Ugolka complex is informative for reconstruction of the geological evolution of the original sediments and determining the stages of formation of thrust-nappe structures.

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43

Scoon, R. N., and H. V. Eales. "Unusual Fe-Ti-Cr spinels from discordant bodies of iron-rich ultramafic pegmatite at the Amandelbult Platinum mine, northwestern Bushveld Complex." Mineralogical Magazine 66, no. 6 (December 2002): 857–79. http://dx.doi.org/10.1180/0026461026660064.

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Abstract Spinels associated with discordant bodies of iron-rich ultramafic pegmatite are described from the Amandelbult Platinum mine in the northwestern part of the Bushveld Complex. The spinels are divided into three groups, disseminated Ti-magnetite, disseminated Fe-Ti-Cr spinel and massive Fe-Ti-Cr spinel. The Fe-Ti-Cr spinels show a range of unusual compositions intermediate between chromite and Ti-magnetite. A relationship was found between stratigraphic height and spinel-type, with the Fe-Ti-Cr spinels restricted to pegmatites from the Upper Critical zone and Ti-magnetite to pegmatites from the Lower Main zone. Ilmenite is a ubiquitous component of all of the pegmatites examined here. The massive Fe-Ti-Cr oxide pegmatites are found only where earlier-formed chromitite layers are juxtaposed with sheet-like bodies of olivine-clinopyroxene pegmatite. A distinct thickening of the original chromitite layers in this situation, and compositional gradients within them, points to accretion of Fe-Ti-Cr spinels onto them prior to partial sub-solidus re-equilibration. Analytical data are presented for these spinels and for the Ti-magnetite. The composition of the Fe-Ti-Cr spinels is not duplicated by cumulus spinels in the Bushveld Complex, but the compositions and microtextures of the disseminated Ti-magnetite are very similar to cumulus Ti-magnetite from the Upper zone. Accordingly, it is deduced that the Ti-magnetite in the pegmatites from the Lower Main zone, together with the ilmenite, crystallized at magmatic temperatures from a suitable Fe-Ti-rich silicate-oxide melt. No evidence has been found to link the pegmatites to hydrothermal fluids. The Cr-rich nature of the disseminated spinels in pegmatites from the Upper Critical zone suggests that the pegmatite melt was richer in chromium at this stratigraphic height, although re-equilibration with earlier-formed cumulus chromite also occurred. Formation of the Fe-Ti-Cr oxide pegmatites reflects a complex process that is incompletely understood and why new oxides plate onto pre-existing chromitite layers that are juxtaposed with Fe-rich ultramafic pegmatites is a matter of conjecture.

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44

Reimann, T., J. Töpfer, and S. Barth. "Low-temperature sintered NTC ceramics for thick film temperature sensors." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2012, CICMT (September 1, 2012): 000536–41. http://dx.doi.org/10.4071/cicmt-2012-wp42.

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Printed thick film NTC thermistors and multilayer devices are frequently used for temperature control in hybrid circuits. NiMn2O4 and substituted spinels are the most established materials for this application. For low-temperature sintering at 900 °C the shrinkage behavior of the thermistor material has to be adjusted by the addition of proper sinter additives. We investigated the chemical stability of NiMn2O4 and substituted spinels in air between 25 °C and 1200 °C. The compound NiMn2O4 is stable from 700 °C to 970 °C only and interacts with the sinter additives. Stable cubic spinels were found in the system ZnxNi0,5Co0,5Mn2-zO4. Addition of liquid phase sintering additives to the spinel powders results in complete densification at 900 °C. No chemical interaction between spinel and additive was observed. The effect of Cu-substitution into the spinel was also investigated. Functional NTC pastes were printed on alumina substrates and post-fired at 900 °C. The NTC thermistor films have a sheet resistivity of about 300 kOhm/sq and B = 3300 K. The firing behavior, microstructure formation and electric properties of NTC thick films will be reported.

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45

BLADES, MORGAN L., JOHN FODEN, ALAN S. COLLINS, TADESSE ALEMU, and GIRMA WOLDETINSAE. "The origin of the ultramafic rocks of the Tulu Dimtu Belt, western Ethiopia – do they represent remnants of the Mozambique Ocean?" Geological Magazine 156, no. 1 (October 30, 2017): 62–82. http://dx.doi.org/10.1017/s0016756817000802.

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AbstractThe East African Orogen contains a series of high-strain zones that formed as Gondwana amalgamated. The Tulu Dimtu shear belt is one of these N–S structures within the Barka–Tulu Dimtu zone in western Ethiopia, and contains ultramafic bodies of equivocal origin. Identifying the petrogenetic origin of these enigmatic rocks provides evidence for the geodynamic significance of these shear zones. Owing to their altered state, these ultramafic rocks’ well-preserved chrome spinels provide the only reliable evidence for their source and tectonic affiliation. Chrome spinels have high Cr2O3 (30.04–68.76 wt %), while recalculated Fe2O3 (< 2 %) and TiO2 (0.01–0.51 %) values are low. The Cr# (molar Cr3+/Cr3+ + Al2+) and Mg# (Mg2+/Mg2+ + Fe2+) have averages of 0.88 and 0.22, respectively. Based on olivine–spinel equilibria, the calculated fO2 values (FMQ +3.03) for the dunites reveal a highly oxidized environment. This spinel chemistry (high Cr# > 0.6 and low Ti) supports a supra-subduction origin, with an oxidized mantle source more refractory than depleted MORB mantle (DMM). These spinel compositions indicate that some ultramafic bodies in western Ethiopia, including those from Daleti, Tulu and Dimtu, are serpentinized peridotites emplaced as obducted ophiolite complexes. By contrast, the ultramafic rocks from the Yubdo locality have a different spinel chemistry, with strong affiliation with igneous spinels formed in Alaskan-style mafic intrusions. These collective results suggest that regardless of their origin as supra-subduction ophiolites or as Alaskan-type intrusions, these spinels were formed on a convergent-subduction margin.

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46

ÖZDEMİR, Evren Görkem. "Comparison of Electronic and Magnetic Properties of 4d Transition Metals Based NbAl2F4 and TcAl2F4 Spinels." Gazi University Journal of Science Part A: Engineering and Innovation 9, no. 4 (December 31, 2022): 452–60. http://dx.doi.org/10.54287/gujsa.1185023.

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Half-metallic properties of NbAl2F4 spinel and semiconductor characteristics of TcAl2F4 spinel were investigated with the help of the WIEN2k program. NbAl2F4 spinel shows a metallic character in the up-electron states, while it has a semiconductor nature in the down-electron states. In NbAl2F4 spinel, the Eg bandgaps were calculated in GGA and GGA+mBJ 1.551 eV and 1.622 eV, respectively. The EHM half-metallic bandgaps were obtained 0.410 eV and 0.422 eV, respectively. In the up-spin states of TcAl2F4 spinel, Eg values were obtained 1.199 eV and 1.447 eV for the GGA and GGA+mBJ methods, respectively, while they were obtained 1.281 eV and 1.519 eV in the down-spin states, respectively. When GGA+mBJ is used, it is easily observed that the semiconductor characters increase. Total magnetic moments of NbAl2F4 and TcAl2F4 spinels were calculated 6.00 µB/cell and 10.0 µB/cell, respectively. When both electronic and magnetic moment values are carefully examined, NbAl2F4 and TcAl2F4 spinels can be used as alternative compounds in spintronic applications.

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47

Arai, S., Y. Shimizu, S. A. Ismail, and A. H. Ahmed. "Low-T formation of high-Cr spinel with apparently primary chemical characteristics within podiform chromitite from Rayat, northeastern Iraq." Mineralogical Magazine 70, no. 5 (October 2006): 499–508. http://dx.doi.org/10.1180/0026461067050353.

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AbstractChemical modification of chromian spinel at low-T alteration was examined in detail for a podiform chromitite from a Tethyan ophiolitic mélange belt at Rayat, northeastern Iraq. The chromitite is highly brecciated and the matrix has been completely altered, producing chlorite and carbonate (dolomite and calcite). High-Cr, low-Fe3+ spinel has formed along the margins and cracks of chromian spinel grains throughout the alteration, associated with unaltered primary spinel and magnetite without ferritchromite. In associated harzburgites, only ferritchromite is found instead of the high-Cr, low-Fe3+ spinel. The high-Cr, low-Fe3+ secondary spinel apparently has chemical properties of mantle origin, plotted at the extension of ordinary mantle spinels on compositional spaces. The character is due to subtraction of Al as chlorite with the addition of an amount of magnetite component from the silicate matrix, which is small in volume relative to peridotite and composed of highly magnesian olivine (up to Fo97). We should treat high-Cr chromian spinels with caution in highly altered mantle-derived rocks, especially chromitite and other rocks with highly magnesian olivine, as well as in detrital particles for provenance study.

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48

Allen, Geoffrey C., and Michael Paul. "Chemical Characterization of Transition Metal Spinel-Type Oxides by Infrared Spectroscopy." Applied Spectroscopy 49, no. 4 (April 1995): 451–58. http://dx.doi.org/10.1366/0003702953964372.

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Standard spinels of the type formed during the oxidation of stainless steel surfaces have been analyzed by infrared techniques. Comparison of the spectra for each series of spinels shows that it is possible to identify the stoichiometry and structure of the spinel from its infrared spectrum.

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49

Andronikov, Alexandre V., Irina E. Andronikova, and Ondrej Pour. "Major and Trace-Element Chemistry of Cr-Spinel in Upper Mantle Xenoliths from East Antarctica." Minerals 12, no. 6 (June 4, 2022): 720. http://dx.doi.org/10.3390/min12060720.

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Cr-spinels in the upper mantle peridotite xenoliths from two Late Mesozoic intrusions of alkaline-ultramafic rocks in Jetty Peninsula (East Antarctica) were studied in situ for their major and trace-element compositions by SEM and LA-ICP-MS. The upper mantle xenoliths were collected from the magmatic bodies “sampled” from different upper mantle domains. One domain was represented by mostly lherzolites (Cpx-poor Spl, Cpx-rich Spl and Spl-Grt) and another one by Spl harzburgites and dunites. Spinels occur as grains of different shapes, sizes and origins. Three main textural types of spinel were identified: primary spinel represented by clean homogeneous grains, a rim of recrystallization/resorption surrounding primary spinel grains and irregular interstitial resorbed grains. Primary spinels are characterized by the concentrations of Al2O3 21–51 wt%, MgO 15–20 wt%, FeO 10–24 wt% and Cr2O3 14–37 wt% with the Cr# of 0.16–0.54. Most trace elements are present in spinels in very low amounts. Only Ti, V, Mn, Co, Ni, Zn and Ga display concentrations in the range of tens to hundreds (up to thousands) ppm. Concentrations of other trace elements vary from below the detection limit to <10 ppm. Spinel major oxide and trace element features allowed the suggestion that the studied upper mantle peridotites represent both simple melt residues and residues strongly influenced by the MORB-like and the SSZ-related melts. The MORB-like melts may be related to the beginning of the Lambert–Amery rift system development, whereas SSZ-like melts could be related to reactivation of SSZ material buried during much earlier amalgamation of East Antarctica.

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50

Zhou, Mei-Fu, Reid R. Keays, Peter C. Lightfoot, Gordon G. Morrison, and Michelle L. Moore. "Petrogenetic significance of chromian spinels from the Sudbury Ignecus Complex, Ontario, Canada." Canadian Journal of Earth Sciences 34, no. 10 (October 1, 1997): 1405–19. http://dx.doi.org/10.1139/e17-113.

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Chromian spinels occur in mafic–ultramafic inclusions in the Sublayer of the Sudbury Igneous Complex (SIC) as well as in mafic–ultramafic rocks in the immediate footwall of the Sublayer. The host rocks are pyroxenite and melanorite with minor dunite, harzburgite, and melatroctolite. As common accessory phases in these rocks, the chromian spinels display euhedral or subhedral forms and are included in olivine and orthopyroxene. Chromian spinel grains generally have ilmenite lamellae and contain abundant inclusions (zircon, olivine, diopside, plagioclase, biotite, and sulfide). All the chromian spinels have similar trace element abundances and are rich in TiO2 (0.5–15 wt.%). They have constant Cr# (100Cr/(Cr + Al)) (55–70) and exhibit a continuum in composition that traverses the normal fields of spinels in a Al–(Fe3+ + 2Ti)–Cr triangular diagram. This continuum extends to that of the composition of chromian magnetite in the host norite matrix to the mafic–ultramafic inclusions. This continuum in composition of the spinels suggests that the noritic matrix to the Sublayer formed from the same magma as the inclusions. A positive correlation between the Cr and Al contents of the spinels was probably produced by dilution of these elements by Fe3+ contributed, perhaps, by a plagioclase-saturated melt. Zircon inclusions in a chromian spinel grain reflect incorporation of crustal, felsic materials into the magma before crystallization of chromian spinel. The chemical characteristics and mineral inclusions of the spinels suggest that the Sublayer formed in response to magma mixing. It is suggested that subsequent to the formation of the crustal melt, mantle-derived high-Mg magmas mixed vigourously with this and generated the magmatic sulfides that eventually formed the Ni – Cu – platinum-group elements sulfide ore deposits. Some of the early crystallization products of the high-Mg magma settled to the chamber floor, where they partially mixed with the crustal melt and formed the mafic–ultramafic inclusions and footwall complexes.

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Journal articles on the topic 'Spinelle'

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