Record details

    A tale of two orogens: the contrasting T-P-t history and geochemical evolution of mantle in high- and ultrahigh-pressure metamorphic terranes of the Norwegian Caledonides and the Czech Variscides
Statement of responsibility
    Hannes K. Brueckner, L. Gordon jr. Medaris
Other titles
    Fifth International Eclogite Conference 1997 (Variant.)
    Brueckner, Hannes K.
    Medaris, L. Gordon, jr.
Source title - serial
    Schweizerische mineralogische und petrographische Mitteilungen
    Roč. 78, č. 2
    8 obr., 3 s.bibl.
    Zkr. název ser.: Schweiz. mineral. petrogr. Mitt.
Subject group
    Český masiv
    datování Sm/Nd
    kolize desek
    metamorfóza vysokotlaká
    podmínky P-T
    vrásnění kaledonské
    vrásnění variské
Geographical name
    Bečváry (Kolín)
    Biskupice (Třebíč)
    Česká republika
    Mohelno (Třebíč)
    Níhov (Žďár nad Sázavou)
    Úhrov (Havlíčkův Brod)
Abstract (in english)
   arnet peridotite (GP) massif within collisional orogenic belts provide windows into deeper levels of the mantle (100 to possibly 400 km) than do spinel peridotites. A geochemical, isotopic and petrological study of GP from high- and ultrahigh-pressure metamorphic terranes in the Western Gneiss Region, Northwegian Caledonides, and the Gföhl Nappe, Bohemian Massif, Czech Variscides, suggest that more than one type of mantle can be involved in continentinent collision. GP from the Western Gneiss Region are chemically, give consistent LT-HP estimates of garnet equilibration, and define old (Pre-Caledonian) Sm-Nd mineral crystallization and recrystallization ages. These ages match similarly old ages in the associated crust, implying that the mantle and crust were coupled.
   The Norwegian peridotites apparently sat in a cold, static mantle environment for a long time before they were incorporated into the Caledonian orogen and are excellent examples of cold, melt-depleted, LIL-poor, buoyant lithosphere of the type that would be expected beneath the Baltic or Laurentian Shield prior to Caledonian collision. GP from the Gföhl Nappe in the Bohemian Massif are more complex than the Norwegian peridotites. Relative to Norwegian GP, they are chemically and mineralogically more heterogenous, some are much more depleted, others are more metasomatized, TP equilibration estimates are much more variable but all formed at significantly pre-Variscan. They seem to represent hot, active mantle that was depleted, metasomatised, recrystallized and stirred by convenction shortly before and during the Variscan Orogeny.
   Some GP (sensu stricto) are believed to represent the lithospheric mantle metasomatized by at least two stages of melt migration that presumably occurred above a subduction zone during the closure of the sea or seas that separed Gondwana and Laurussia. Other "transitional" (i.e. spinel-bearing) GR are believed to represent hot asthenosphere that penetrated the lithosphere and rose to the base of the orogen during the colli
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
Entered date
    18. 2. 2008
Import date
    8. 8. 2012