PUMA
Istituto di Geoscienze e Georisorse     
Raade G., Bernhard F., Ottolini L. Remplacement textures involving four scandium silicate minerals in the Heftetjern granitic pegmatite, Norway. In: European Journal of Mineralogy, vol. 16 (6) pp. 945 - 950. Schweizerbart, 2004.
 
 
Abstract
(English)
Four late-hydrothermal scandium silicate minerals, related by replacement textures, were studied by EMPA and SIMS. Textural evidence shows that early-formed thortveitite is broken up by bazzite and scandian milarite, which seem to occur in equilibrium. Thortveitite is also partly replaced by kristiansenite. The two steps of alteration involve first the introduction of fluids rich in Be, K, Ca and Cs to form bazzite and milarite and then Ca and Sn for the formation of kristiansenite. Addition of water accompanies both steps. Thortveitite is unusually rich in SnO₂ (up to 5.67 wt. %). The amount of Sn is balanced by Mn according to the substitution scheme 2Scł⁺ ⇔ Sn⁴⁺ + MnČ⁺. Bazzite is strongly zoned with respect to Cs and has up to 8.55 wt. % Cs₂O. The alkali content in the structural channels is balanced by FeČ⁺ and MnČ⁺ substituting for Sc. Scandian milarite is close to the end-member formula K(CaSc)Be₃(Si₁₂O₃₀) with nearly all Al replaced by Be and half of the Ca atoms by Sc. Kristiansenite is very near to the ideal formula Ca₂ScSn(Si₂O₇)(Si₂O₆OH).
URL: http://www.schweizerbart.de/j/ejm/
DOI: 10.1127/0935-1221/2004/0016-0945
Subject thortveitite
kristiansenite
scandian milarite
cesian bazzite
chemical analysis
Norway


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