Podrobnosti záznamu

Název
    Geochemistry of agates: a trace element and stable isotope study
Údaj o odpovědnosti
    J. Götze, M. Tichomirova, H. Fuchs, J. Pilot, Z.D. Sharp
Autor
    Fuchs, H.
    Götze, J.
    Pilot, J.
    Sharp, Z. D.
    Tichomirova, M.
Jazyk
    anglicky
Zdrojový dokument - seriál
    Chemical geology (including isotope geoscience)
Svazek/č.
    Vol. 175, no. 3-4
Strany
    p. 523-541
Rok
    2001
Poznámky
    8 obr., 2 fot., 4 tab., 2 s.bibl.
    il.
    Zkr. název ser.: Chem. Geol. (Isotope Geosci.)
Předmětová skupina
    achát
    andezit
    bazalt
    hydrotermální alterace
    izotopy C
    izotopy H
    izotopy stabilní
    kalcit
    paleozoikum-svrchní
    podkrkonošská pánev
    prvky stopové
    přesycení
    roztok vodný
    ryolit
    skupina SiO2
    vzácné zeminy
Geografické jméno
    Brazílie-Rio Grande do Sul
    ČR-Čechy
    Frýdštejn (Jablonec nad Nisou)
    Kanada
    Kyje (Jičín)
    Mexiko
    Namibie
    Nová Paka (Jičín)
    SRN
    Velká Británie-Scotland
Klíčové slovo
    Agates
    Element
    Geochemistry
    Isotope
    Stable
    Study
    Trace
Abstrakt (anglicky)
   Agate samples of acidic, intermediate and basic volcanics from 18 localities around the world and of different age (Precambrian to tertiary) were studied by trace element and stable isotope analysis to provide information about the process of agate formation and the origin of mineral-forming fluids. trace element data are similar for agates from acidic and basic volcanics. The general chondrite-normalized REE distribution pattern is characterized by a slope from La to Lu with enriched LREE and a positive Eu anomaly in some samples. The similarity in the shape of the REE patterns between agates and the parent volcanic rocks suggests that the element are mobilized by circulating fluids during syn- and postvolcanoc alteration of the volcanic wall rocks. Observed positive Eu anomalies in agates probably originate from feldspar alteration. Deuterium and oxygen isotope analyses of agates and associated quartz incrustations (delta: -44%. to -130%.;delta18O: +16.4%.
   to 33.4%.) reveal variations in isotopic composition between samples of different localities but also within single agate samples (up to 10% for delta18O). In general, oxygen isotope compositions become heavier as volcanic host rocks grow more acidic. Furthermore, agates have higher delta18O values than associated quartz incrustations. Variations within single agate samples can be explained either by kinetic effects during isotope fractionation (e.g. the formation of agate from a noncrystalline precursor) or by mixing processes of meteoric and magmatic fluids
Přispěvatel
    Česká geologická služba
Kód přispěvatele
    ČGS (UNM)
Zdrojový formát
    U
Datum vložení
    23. 8. 2007
Datum importu
    8. 8. 2012