Podrobnosti záznamu

Název
    EVOLUTION OF THE CINOVEC (ZINNWALD) GRANITE CUPOLA, CZECH REPUBLIC: COMPOSITION OF FELDSPARS AND MICAS, A CLUE TO THE ORIGIN OF W, Sn MINERALIZATION
Autor
    Johan, Vera
    Johan, Zdenek
    Strnad, Ladislav
Jazyk
    anglicky
Typ dokumentu
    článek v periodiku
Zdrojový dokument - seriál
    Canadian Mineralogist
Svazek/č.
    Roč. 50, č. 4
Strany
    18
Rok
    2012
Výraz tezauru
    Cinovec (Zinnwald)
    Czech Republic
    F-rich fluid
    granite cupola
    lithian annite
    lithian annite -> zinnwaldite transformation
    metallogenic model
    Sn, Nb, Ta and W concentrations in micas
    zinnwaldite
Klíčové slovo
    CINOVEC
    CLUE
    COMPOSITION
    CUPOLA
    CZECH
    EVOLUTION
    FELDSPARS
    GRANITE
    MICAS
    MINERALIZATION
    ORIGIN
    REPUBLIC
    Sn
    ZINNWALD
Abstrakt (anglicky)
   A 1596-m-deep borehole (CS-1) located in the central part of the Cinovec (Zinnwald) granite cupola mineralized in Sn and W intersected zinnwaldite granite (ZG) followed by lithian annite ("protolithionite") granite (PG). These two types of granite are separated by a transition zone (TZ). We studied the chemical composition of major mineral phases (plagioclase, K-feldspar, micas) by EPMA and LA-ICP-MS analyses. The plagioclase composition corresponds to albite (Ab(99.6-91.1)) containing 0.09 to 0.18 wt.% Rb2O. Albite crystallized from the magma. K-feldspar is perthitic and shows an increase in Rb concentration (up to 0.83 wt.% Rb2O) in the apical part of the cupola. The partition coefficient K-D-Rb(Mi-Kfs) is constant throughout the cupola, indicating a systematic re-equilibration of these two minerals with fluid. Lithian annite occurs below -735 m. Its F content decreases with depth and from -940.5 m, OH exceeds F. Magnesium and Ti concentrations show a remarkable positive correlation
   with depth. The TZ and adjacent area are characterized by strong variations in the chemical composition of micas, reflecting the fluctuation of saturation-oversaturation of residual liquid by a F-rich fluid phase. The Rb concentration in zinnwaldite (up to 2 wt.% Rb2O) strongly increases in the apical part of the cupola owing to a significant transfer of volatiles. The chemical composition of mica evolves gradually from the TZ to the apical zone. The discovery of lithian annite included in quartz at -97 m indicates the formation of zinnwaldite by interaction of lithian annite with F-rich fluid. The octahedral site of lithian annite allows the incorporation of Sn, Nb, Ta and W, replacing Ti. Because of the lithian annite -> zinnwaldite transformation, these elements with higher ionic charges are expelled from the mica structure, transferred to the fluid phase and concentrated in the apical part of the cupola.
Přispěvatel
    UK Praha, Přírodovědecká fakulta
Kód přispěvatele
    UK, PřF
Zdrojový formát
    R
Datum importu
    27. 4. 2014