Clinopyroxene from an alkali pyroxenite xenolith, Louená-Oberwiesenthal Volcanic Centre, Bohemian Massif: crystal chemistry and structure

• Autorzy: Ulrych D. , Niznansky D. , Pertlik F. , Giester G. , Ertl A. , Brandstätter F.
• Języki publikacji: EN

Abstrakty

EN

Alkali pyroxenite (and ijolite) xenoliths occur in the Tertiary Loučná-Oberwiesenthal Volcanic Centre associated with the Ohře/Eger Rift. The alkali pyroxenite xenoliths represent fragments of an intracrustal complex with Sr-Nd isotope ratios consistent with mantle sources of HIMU-affinity. The crystal structure of diopside from an alkali pyroxenite xenolith with the formula (...) and the lattice parameters a = 9.773(2), b = 8.886(2), c = 5.308(1) [] and = 105.89(3) [°] was refined to an R-value of 0.025 for 1174 reflections. The mean interatomic distances are: within theMe1-O6 octahedron <2.067> , within theMe2-O8 polyhedron <2.498> . The last value reflects the occupation of this atomic position by significant amounts of Fe2+ and Ti4+. The enlargement determined for the bond length to 1.657 is in accordance with the site population for this position: (Si1.69Al0.31). The molar ratio Fe2+/Fe3+ determined by Mössbauer spectroscopy is equal to 0.786. The AlIV deficiency in T-sites of clinopyroxene of rims is negligible (up to 0.019 a.p.f.u.) restricted to sporadic local electronmicroprobe analyses. The presence of Fe3+ in the T-position of Si- and Al-poor clinopyroxenes was not confirmed by X-ray structural analyses because of its low quantity. Nevertheless, the Mössbauer spectroscopy measurements (isomer shift of 0.36 mm/s) imply that Fe3+ is present only in the Me1-O6 positions.

Słowa kluczowe

EN

Krušné hory/Erzgebirge Mts.; lower crust origin; alkali pyroxenite xenoliths; crystal chemistry; crystal structure; clinopyroxene

• Wydawca: Państwowy Instytut Geologiczny - Państwowy Instytut Badawczy
• Czasopismo: Geological Quarterly
• Rocznik: 2006
• Tom: Vol. 50, No. 2
• Strony: 257--264
• Opis fizyczny: tab., wykr., bibliogr. 27 poz.

Twórcy

autor

Ulrych D.

autor

Niznansky D.

autor

Pertlik F.

autor

Giester G.

autor

Ertl A.

autor

Brandstätter F.

• Institute of Geology, Academy of Sciences of the Czech Republic, Rozvojová 135, 165 02 Prague 6, Czech Republic,

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