and jinshajiangite from the Gremyakha-Vyrmes alkaline complex,
Lykova I.S.*, Pekov I.V.*,*, Kononkova N.N.**, Shpachenko A.K.***
**Vernadsky Institute of Geochemistry and Analytical Chemistry RAS,
The layered titanosilicates bafertisite,
Áand jinshajiangite, NaBaFe4Ti2O(Si2O7)2(OH)
Minerals of the bafertisite group were not reported from
Gremyakha-Vyrmes before. For jinshajiangite, it is first find in
The described minerals were found in a pegmatite
related to alkaline granites at northern coast of the Gremyakha lake. Jinshajiangite occurs
as needle-shaped crystals up to
Bafertisite and jinshajiangite have been identified by chemical, X-ray diffraction and infrared spectroscopy data.
The X-ray powder patterns of bafertisite and jinshajiangite from Gremyakha-Vyrmes are similar to ones of these minerals studied earlier (Kuan Ya-Hsien et al., 1963; Hong Wenxing, Fu Pinqiu, 1982). The main basal reflection (002) of Kola jinshajiangite is characterized by the interplanar spacing 10.40 Å, the 001 reflex of Kola bafertisite is 10.95 Å.
The chemical composition of bafertisite and jinshajiangite was studied using the electron microprobe. Formulae were calculated basing on 4(Si+Al). All iron was considered as bivalent, the O/OH ratio was calculated by charge balance. The empirical formulae (cations have groupped according to structural data for the minerals) are:
The Kola jinshajiangite differs from the original Chinese sample in higher value of the Mn/Fe ratio and lower value of the Nb/Ti ratio and lower F content. The Swedish mineral occupies intermediate position in its Mn/Fe ratio.
In its chemical composition, bafertisite
from Gremyakha-Vyrmes is similar to bafertisite from its type locality, the
Bayan Obo alkaline complex,
Chemically, bafertisite and jinshajiangite from Kola differ one from other not only in part of species-defining sodium and barium cations but also in subordinate constituents. Bafertisite is characterized by higher content of fluorine and lower content of niobium. Concentration of calcium in Kola bafertisite is below detection limit whereas in our jinshajiangite, Ca, undoubtedly replacing Na, is significant admixture.
Barium minerals were not found in the Gremyakha-Vyrmes alkaline granites and their derivatives before (Polkanov et al., 1967; Bulakh, 1997). Ba was accumulated probably because of its mobilization from potassium feldspar as a result of albitization of granite interacted with feldspathoid rocks, namely nepheline syenites and ijolites.
This study was supported by grant of President of Russain Federation No. 863.2008.5 and grant of Russian Science Support Foundation (I.V.P.).
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