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N. V. Sorokhtina N. V. Chukanov A. V. Voloshin Ya. A. Pakhomovsky A. N. Bogdanova M. M. Moiseev 《Geology of Ore Deposits》2008,50(7):620-628
Cymrite, BaAl2Si2O8 · nH2O, is a rare mineral formed during low-grade dynamothermal metamorphism (T = 250–300°C, P = 1–3 kbar). Cymrite has been described from many metasedimentary ores and hydrothermal rocks. In carbonatites, it has been found for the first time. Cymrite has been identified in the Kovdor and Seblyavr massifs, Kola Peninsula. In Kovdor, this mineral has been described from one of the hydrothermal veins cutting the pyroxenite-melilitite-ijolite complex at the Phlogopite deposit; cymrite is associated with thomsonite, calcite, and stivensite. In the Seblyavr pluton, cymrite occurs in thin veins of calcite carbonatite that cut pyroxenite contacting with ijolite. Cymrite from the Seblyavr pluton is associated with calcite, natrolite, pyrite, and chalcopyrite. The mineral is optically negative and uniaxial, with extinction parallel to elongation; ω ～ 1.607(1). According to X-ray diffraction data, cymrite from Seblyavr is monoclinic, space group P1m1; unit-cell dimensions are: a = 5.33, b = 36.96, c = 7.66 Å, β = 90°, V = 1510.55 Å3. According to the results of IR spectroscopy, in the series of samples from different massifs (in the running order Kovdor-Voishor-Seblyavr), the double-layer deformation is enhanced and accompanied by a decrease in the Si-O-Si angle and weakening of hydrogen bonds of interlayer water. The empirical formulas of cymrite calculated from electron microprobe analyses are Ba0.93–0.95Ca0.01–0.02K0.00–0.05Na0.02–0.04Al1.97–2.01Si1.99–2.03O8(H2O) and Ba1.00–1.02Ca0.00–0.01Sr0.00–0.01Fe0.00–0.01Al1.94–2.00Si1.98–2.03O8(H2O) at Seblyavr and Kovdor, respectively. Cymrite from the carbonatite massifs of the Kola Peninsula was formed under hydrothermal conditions at low temperature (200–300°C), high activity of Ba and Si, and high water pressure. At Kovdor, the mineral crystallized directly from the residual solution enriched in Ba. The sequence of mineral deposition is as follows: thomsonite-cymrite-calcite-stevensite. Cymrite from the Seblyavr pluton is a product of hydrothermal alteration of primary Na-K-Ba silicates of ijolite: nepheline, feldspar, and probably celsian. Natrolite replaces cymrite indicating high alkalinity of late hydrothermal fluids. 相似文献
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At the Petropavlovsk-Kamchatsky geodynamic test site the instrumental complex has operated for the registration of subsurface gas concentration since 2006. In this paper the main components of the complex and their capabilities are described. To illustrate the work of the complex the dynamics of subsurface gas concentrations in the period from February to March 2011 (before and after the earthquake off the coast of Japan, March 11, 2011, M = 9.0) in one of the registration points was analyzed. These data indicate geodynamic processes during this period in the considered area at the point of subsurface gas registration. Selected dynamics anomalies of the subsurface gas concentrations can be regarded as a short-term remote precursor of the earthquake off the coast of Japan. 相似文献
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Geology of Ore Deposits - Many massive sulfide ore occurrences and deposits in the Kola region are located within the Paleoproterozoic Pechenga–Imandra–Varzuga rift belt (2.5–1.7... 相似文献
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I. V. Pekov N. V. Chukanov N. N. Kononkova O. V. Yakubovich W. Massa A. V. Voloshin 《Geology of Ore Deposits》2009,51(7):595-607
Tveitite-(Y) as pods up to 10 cm across has been found at Mt. Rovgora, the Western Keivy, Kola Peninsula, Russia, in an albite-quartz-amazonite pegmatite vein related to alkaline granite. Tveitite-(Y) grains (up to 4 cm) are parallel microintergrowths of two isostructural varieties, Ca9.5Na1.7Y5.2Ln2.0F42.6 and Ca11.4Na1.9Y4.4Ln1.4F42.0. The idealized structural formula (Z = 3) is (Y, Na)6(Ca, LREE)6(Ca, Na, HREE)6(Ca, Na)F42; the simplified formula is (Ca, REE, Na)13(Y, Na)6F42; space group R \(\bar 3\) a = 17.020, c = 9.679 Å. [Lanthanoides are abbreviated in this paper as Ln, whereas Ln + Y as REE]. Nine fluorite samples containing from 0 to 18 mol % (REE)F3 were examined by electron microprobe, X-ray powder diffraction, and IR spectroscopy. The crystal structure of natural yttrofluorite has been determined for the first time (R aniso = 1.47 %): Fm3m, a = 5.493 Å; the structural formula is (Ca0.82Y0.12Ln0.06)F2.15. Earlier published and new data show that yttrofluorite containing (REE)F3 > 20 mol % and REE-enriched fluorite with LREE > Y (HREE) are metastable under room conditions. In nature, tveitite-(Y) is a product of solid-state transformation of metastable yttrofluorite with (REE)F3 > 20 mol %. Inferred protophases could have been exsolved into tveitite-(Y) variable in composition or tveitite-(Y) + yttrofluorite stable under normal conditions. The formation of tveitite-(Y) requires the erichment of a protophase not only in Y but also in LREE and HREE as stabilizing admixtures regularly distributed by different types of Ca-dominant structural sites. Tveitite-(Y) and yttrofluorite are geochemical indicators of a medium that is not only enriched in Y, Ln, and F, but also depleted in Na, Ca, CO2 and P. 相似文献
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