Podrobnosti záznamu

Název
    From explosive breccia to unidirectional solidification textures: magmatic evolution of a phosphorus- and fluorine-rich granite system (Podlesí, Krušné hory Mts., Czech Republic)
Údaj o odpovědnosti
    Karel Breiter
Další názvy
    International workshop "Phosphorus- and Fluorine-rich Fractionated Granites", October 16-19, 2001, Podlesí, Czech Republic (Variant.)
Autor
    Breiter, Karel
    Breiter, Karel, 1956-
Jazyk
    anglicky
Typ dokumentu
    článek v periodiku
Zdrojový dokument - seriál
    Bulletin of the Czech Geological Survey-Věstník Českého geologického ústavu
    Věstník Českého geologického ústavu (Bulletin of the Czech Geological Survey)
Svazek/č.
    Roč. 77, č. 2
Strany
    26
    s. 67-92
Rok
    2002
Poznámky
    12 obr., 4 fot., 6 tab., 2 s. bibl.
    il.
    Zkr. název ser.: Věst. Čes. geol. Úst. (Bull. Czech geol. Surv.)
Předmětová skupina
    brekciace
    chemismus hornin
    fluór
    fosfor
    granit
    intruze stratiformní
    krušnohorský pluton
    složení peraluminické
    vzorek celé horniny
Výraz tezauru
    granite, brecciation, layered intrusion, unidirectional solidification textures, chemical composition, fluorine, phosphorus, Krušné hory Mts, Bohemian Massif
Geografické jméno
    ČR-Čechy
    Krušné hory
    Podlesí (Karlovy Vary)
Klíčové slovo
    Breccia
    Czech
    Evolution
    Explosive
    Fluorine-rich
    Granite
    Hory
    Krušné
    Magmatic
    Mts
    Phosphorus-
    Podlesí
    Republic
    Solidification
    System
    Textures
    Unidirectional
Abstrakt (anglicky)
   The Podlesí granite stock in western Krušné Hory Mts. represents the most highly fractionated part of the late Variscan Nejdek-Eibenstock pluton. Internal fabric of the stock has been studied in several boreholes up to 350 m deep.The granite stock is intercalated with several generally flat-lying dykes of albite-zinnwaldite-topaz granite. A prominent example of layering with unidirectional solidification textures (UST) was found in the upper part of this major dyke.Following evolutionary model was developed: The rapid emplacement of F, P, Li-rich granite melt was accompanied by brecciation of the overlying phyllites. Further fractionation produced a small amount of extreme F,P,Li- and water-rich meltwhich later intruded as system of flat dykes. Nonequilibrium crystallisation of undercooled melt in the dykes produced line rock with unidirectional crystallisation texture.

   The Podlesí granite stock in western Krušné hory Mts. represents the most highly fractionated part of the late Variscan Nejdek-Eibenstock pluton. Internal fabric of the stock has been studied in several boreholes up to 350 m deep. The stock is composed of two tongue-like bodies of albite-protolithionite-topaz granite (stock granite) coalesced at depth, which were emplaced into Ordovician phyllite and biotite granite of younger intrusive complex (YIC) of the Nejdek pluton. The uppermost part of the intrusion is bordered by a layer of marginal pegmatite (stockscheider) up to 50 cm thick. Explosive breccia was found as an isolated block at the southwest contact of the stock. It is comprised of fragments of phyllite several millimetres to 5 cm in size cemented with fine-grained granitic matrix similar to the stock granite, but very fine-grained.
   Within the uppermost 100 m, the stock granite is intercalated with several mostly flat-lying dykes of albite-zinnwaldite-topaz granite (dyke granite). Upper and lower contacts of the dykes are sharp, flat, but in detail slightly uneven. The thickest dyke (about 7 m) outcrops in an old quarry. A prominent example of layering with unidirectional solidification textures (UST) was found in the upper part of this major dyke. Individual Q-Afs laminae are separated by comb quartz layers and/or by layers of oriented fan-like zinnwaldite aggregates. A pegmatite-like layer with oriented megacrysts of Kfs up to 6 cm long was encountered in the uppermost part of the dyke. One thin layer of fine-grained quartz with oriented Kfs-megacrysts was found within the stock granite. Post-magmatic processes, particularly greisenisation, developed only to a limited degree. The uppermost flat dyke of the dyke granite was partly greisenised into white quartz-rich (+topaz, Li-mica, wolframite) greisen.
   Scarce thin, steep stringers of biotite greisen were encountered over the entire outcrop and in drilled parts of the stock granite and surrounding biotite granite. The stock granite is strongly peraluminous (A/CNK 1.15-1.25), enriched in incompatible elements such as Li, Rb, Cs, Sn, Nb, W, and poor in Mg, Ca, Sr, Ba, Fe, Sc, Zr, Pb, and V. The rock is rich in phosphorus (0.4-0.8 wt per cent P2O5) and fluorine (0.6-1.8 wt per cent F). A high degree of magmatic fractionation is demonstrated by low K/Rb and Zr/Hf ratios (22-35 and 12-20, respectively) and high U/Th ratio (4-7). The dyke granite is even more enriched in Al (A/CNK = 1.2-1.4), P (0.6-1.5 wt per cent P2O5), F (1.4-2.4 wt per cent), Na, Rb, Li, Nb, Ta, and depleted in Si, Zr, Sn, W and REE. The K/Rb (14-20) and Zr/Hf (9-13) ratios are lower than in the stock granite.
   Based on all available data, the following evolutionary model was developed: Pronounced fractionation of the YlC-melt (=Younger Intrusive Complex of the Nejdek pluton) produced small amount of residual F, P, Li-rich melt (stock granite melt) which was emplaced at a "shallow depth" as a tongue-like
Přispěvatel
    Česká geologická služba
Kód přispěvatele
    ČGS (RIV)
    ČGS (UNM)
Zdrojový formát
    R
    U
Datum vložení
    5. 2. 2009
Datum importu
    8. 8. 2012
    15. 10. 2014