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Browsing by Subject "Buntsandstein"

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    Item type:Article, Access status: Open Access ,
    Fasetowane ziarna granatów z pstrego piaskowca monokliny przedsudeckiej okolicy Głogowa (SW Polska)
    (Wydawnictwa AGH, 2007) Muszyński, Marek; Gaweł, Adam; Skowroński, Andrzej
    The authors studied (optical microscopy, SEM/EDS, XRD, IR) the so-called faceted garnets found in heavy mineral fractions, separated out from the sandstones of the Buntsandstein on the Fore-Sudetic Monocline. The garnets represent almandine members of the almandine-pyrope series (almandine prevails over pyrope) and usually contain a subordinate admixture of the grossular member, whereas are devoid of the spessartine member. An alimentation area of these minerals was probably situated in the Sudetes, where garnets with a similar composition occur in some exposed rocks of the eclogite and granulite facies. The authors agree with currently prevailing opinions that the faceted garnets (co-occurring with rounded grains of zircon, tourmaline, rutile, apatite, and even mica flakes) were formed due to their selective diagenetic leaching by porous solutions. The process must have proceeded slowly in an alkaline or, possibly, neutral environment (it is proved by the presence of unleached apatite and domination of smectites in the bounding mass of the sandstones), under conditions approaching chemical equilibrium between garnets and the porous solutions.