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V. V. Yarmolyuk D. A. Lykhin T. N. Shuriga A. A. Vorontsov A. M. Sugorakova 《Geology of Ore Deposits》2011,53(5):390-400
The Snezhnoe phenakite-beryl deposit is one of the highest-grade deposits in the Altai-Sayan beryllium province. This deposit
is spatially associated with the alkali granite of the Ognit Complex and localized in the apical part of the granitic pluton.
The trace element composition of granite, as well as of Be and Ta-Nb ores was studied. The Rb-Sr age of Be mineralization
estimated at 305 Ma is consistent with the time of formation of numerous rare-metal alkali granitic plutons in the Eastern
Sayan and the eastern Tuva. The region of these granitic plutons is outlined as the Late Paleozoic East Sayan rare-metal metallogenic
zone specialized for Nb, Ta, Be, Li, Zr, Th, and REE mineralization. The East Sayan zone is localized in the marginal part
of the Barguzin igneous province and is similar to the marginal zone of this province in composition of igneous associations
and metallogenic specialization. The formation of the Barguzin igneous province and the East Sayan metallogenic zone is related
to the evolution of the Late Carboniferous-Early Permian mantle plume. 相似文献
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The paper proposes pioneering data on the polarized optical absorption spectra of Li-Fe micas: intermediate members of the siderophyllite-zinnwaldite-polylithionite and annite-protolithionite-zinnwaldite-trilithionite series with variable Fe and Li proportions and Li- and Fe-bearing muscovite (phengite). Based on the analysis of structural data, the complicated structure of the Fe2+ → Fe3+ charge transfer band in the mica structures is explained, and arguments are presented to justify the ascribing of its shortwave component (CTB-1, ν = 17200-14900 cm?1) to charge transfer in the pair Fe2+(M2) → Fe3+(M2) and the longwave component (CTB-2, ν = 14200-13600 cm?1) to charge transfer in the pair Fe2+(M1) Fe3+(M2). It is demonstrated that the anomalous shift of the superposition of two-component CTB toward the shortwave region, to 17000 cm?1, results from a decrease in the length of oxygen edges between adjacent M2M2 and M1M2 tetrahedrons when Li is accommodated in the mica structure. The first data are presented on the spectrum of Fe2+ ions in large distorted M3(M1) tetrahedrons (OAC Fe2+ II) in hetero-octahedral Li micas (zinnwaldite), and the behavior of the corresponding absorption bands at 11400 and 8000 cm?1 is determined. It is proved that characteristics of the optical spectra of Fe2+ ions can be used as an indicator of the structure of the octahedral layer in the mica structures. Results of the comparative analyses of spectral parameters of the Fe2+ → Fe3+ charge transfer, crystal field spectra of Fe2+ ions, and the crystal-chemical characteristics controlling them in micas of the polylithionite-siderophyllite series are completely consistent with the character of cation ordering in the crystal structures of these micas determined by X-ray diffraction analysis. 相似文献
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A reliable criterion of quartz genesis is proved to be ratios of the concentrations of structural defects in this mineral,
which are a function of its structural dynamic state. Within the scope of the theory of sparring defects, theoretical dependences
were derived for concentrations of various minor components accommodated in the quartz structure during two stages of isomorphism.
It was determined that structurally dynamic equilibrium may be established in quartz with time and this equilibrium “obliterates”
genetic information on the crystallization conditions. The conclusions obtained in this research are confirmed by data on
pervasively occurring relations between the distributions of isomorphous components in quartz samples from rare-metal deposits
of various genetic types. 相似文献
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