Pyroxenoids of pyroxmangite–pyroxferroite series from xenoliths of Bellerberg paleovolcano (Eifel, Germany): Chemical variations and specific features of cation distribution


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Аннотация

The pyroxferroite and pyroxmangite from xenoliths of aluminous gneisses in the alkaline basalts of Bellerberg paleovulcano (Eifel, Germany) have been studied by electron-probe and X-ray diffraction methods and IR spectroscopy. The parameters of the triclinic unit cells are found to be a = 6.662(1) Å, b = 7.525(1) Å, c = 15.895(2) Å, α = 91.548(3)°, β = 96.258(3)°, and γ = 94.498(3)° for pyroxferroite and a = 6.661(3) Å, b = 7.513(3) Å, c = 15.877(7) Å, α = 91.870(7)°, β = 96.369(7)°, and γ = 94.724(7)° for pyroxmangite; sp. gr. \(P\overline 1 \). The crystallochemical formulas (Z = 2) are, respectively, M(1–2)(Mn0.5Ca0.4Na0.1)2M(3–6)(Fe, Mn)4M7[Mg0.6(Fe, Mn)0.4][Si7O21] and M(1–3)(Mn, Fe)3M(4–6)[(Fe, Mn)0.7Mg0.3]3M7[Mg0.5(Fe, Mn)0.5][Si7O21]. For these and previously studied representatives of the pyroxmangite structural type, an analysis of the cation distribution over sites indicates wide isomorphism of Mn2+, Fe2+, and Mg in all cation M(1–7) sites and the preferred incorporation of Сa and Na into large seven-vertex M1O7 and M2O7 polyhedra and Mg into the smallest five-vertex M7O5 polyhedron.

Авторлар туралы

N. Shchipalkina

Moscow State University; Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics,”

Хат алмасуға жауапты Автор.
Email: estel58@yandex.ru
Ресей, Moscow; Moscow, 119333

S. Aksenov

Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics,”; Nesmeyanov Institute of Organoelement Compounds

Email: estel58@yandex.ru
Ресей, Moscow, 119333; Moscow

N. Chukanov

Institute of Problems of Chemical Physics

Email: estel58@yandex.ru
Ресей, Chernogolovka, Moscow oblast, 142432

I. Pekov

Moscow State University

Email: estel58@yandex.ru
Ресей, Moscow

R. Rastsvetaeva

Moscow State University

Email: estel58@yandex.ru
Ресей, Moscow

C. Schäfer

Südwestdeutsche Salzwerke AG

Email: estel58@yandex.ru
Германия, Heilbronn, 74076

B. Ternes

Aff6

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Германия, Bahnhofstrasse 45, Mayen, 56727

W. Shüller

Aff7

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Германия, Im Straussenpesch 22, Adenau, 53518

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