Podrobnosti záznamu

Název
    Fluorine variation in hambergite from granitic pegmatites
Údaj o odpovědnosti
    Milan Novák, Peter C. Burns, George B. Morgan VI
Další názvy
    Granitic pegmatites: The Černý - Foord volume (Variant.)
Autor
    Burns, Peter C.
    Morgan VI, George B.
    Novák, Milan, 1952-
Jazyk
    anglicky
Zdrojový dokument - seriál
    Canadian mineralogist
Svazek/č.
    Vol. 36, no. 2
Strany
    p. 441-446
Rok
    1998
Poznámky
    1 obr., 4 tab., 22 bibl.
    Francouzské resumé
    il.
    Zkr. název ser.: Canad. Mineralogist
Předmětová skupina
    boráty
    chemismus minerálů
    fluor
    krystalizace
    lithium
    mineralogie topografická
    moldanubikum
    pegmatit
    textura miarolitická
    vlastnosti optické
Geografické jméno
    Ctidružice (Znojmo)
    Česká republika
    Kracovice (Třebíč)
    Sušice (Klatovy)
    USA-California
Klíčové slovo
    Fluorine
    Granitic
    Hambergite
    Pegmatites
    Variation
Abstrakt (anglicky)
   Considerable F-for-OH substitution can occur in the structure of hambergite, Be2(BO3)(OH,F). The substitution results in a nnear reduction of the indices of refraction. This relation can be used to estimate the F content of hambergite, subject to the constraint that samples may be compositionally heterogeneous. Previous X-ray-diffraction studies of five crystals of hambergite showed that increasing amounts of F for OH lead to a decrease in the a dimension and an expansion of the b dimension. The F content of hambergite may be readily estimated if the unit-cell dimensions are known. Although originally described from an alkaline syenitic pegmatite, the majority of hambergite occurrences are in complex Li-rich granitic pegmatites of the elbaite or transitional elbaite-lepidolite subtypes. Hambergite occurs as a comparatively early phase in massive pegmatites from several localities in the Czech Republic.
   More commonly, hambergite is a late-crystallizing phase produced in miarolitic pockets as the hishly evolved magma approaches its solidus. The F content of hambergite from pegmatites appears to reflect the F activity of the medium (melt or fluid) from which it crystallizes. Hambergite found in miarolitic pockets is typically more homogeneous in composition and commonly has a lower F content than that found in a massive pegmatite, although F-rich examples from pegmatitic pockets also are observed. It is unclear whether the lower F content of hambergite from miarolitic pockets, is strictly a result of crystallization in lower-F systems, or involves precipitation in equilibrium with exsolved aqueous fluids
Přispěvatel
    Česká geologická služba
Kód přispěvatele
    ČGS (UNM)
Zdrojový formát
    U
Datum vložení
    16. 4. 2008
Datum importu
    8. 8. 2012