2019
Monazite Behaviour during Metamorphic Evolution of a Diamond-bearing Gneiss: a Case Study from the Seve Nappe Complex, Scandinavian Caledonides
PETRIK, Igor; Marian JANAK; Iwona KLONOWSKA; Jaroslaw MAJKA; Nikolaus FROITZHEIM et al.Základní údaje
Originální název
Monazite Behaviour during Metamorphic Evolution of a Diamond-bearing Gneiss: a Case Study from the Seve Nappe Complex, Scandinavian Caledonides
Autoři
PETRIK, Igor; Marian JANAK; Iwona KLONOWSKA; Jaroslaw MAJKA; Nikolaus FROITZHEIM; Kenta YOSHIDA; Vlasta SASINKOVA; Patrik KONECNY a Tomáš VACULOVIČ
Vydání
Journal of Petrology, Oxford, Oxford University Press, 2019, 0022-3530
Další údaje
Jazyk
angličtina
Typ výsledku
Článek v odborném periodiku
Obor
10403 Physical chemistry
Stát vydavatele
Velká Británie a Severní Irsko
Utajení
není předmětem státního či obchodního tajemství
Odkazy
Impakt faktor
Impact factor: 3.451
Označené pro přenos do RIV
Ano
Kód RIV
RIV/00216224:14310/19:00117920
Organizační jednotka
Přírodovědecká fakulta
UT WoS
EID Scopus
Klíčová slova anglicky
monazite; diamond; subduction; UHP metamorphism; Scandinavian Caledonides
Štítky
Příznaky
Mezinárodní význam, Recenzováno
Změněno: 20. 1. 2021 11:36, Mgr. Marie Novosadová Šípková, DiS.
Anotace
V originále
Monazite is a common mineral in metapelitic rocks including those that underwent ultrahigh-pressure (UHP) metamorphism. During metamorphic evolution monazite adapts its composition to the changing mineral assemblage, especially in its heavy rare earth element contents. We studied this process in diamond-bearing gneiss containing monazite, from Saxnas in the Seve Nappe Complex of the Scandinavian Caledonides. Although the rock has been re-equilibrated under granulite-facies and partial melting conditions, it still preserves minerals from the UHP stage: garnet, kyanite, rutile, and especially diamond. Microdiamonds occur in situ as inclusions in garnet, kyanite and zircon, either as single crystals or as polyphase inclusions with Fe-Mg carbonates, rutile and CO2. Both monazite and diamond occur in the rims of garnet showing the highest pyrope content and a secondary peak of yttrium. Such a position indicates thermally activated diffusion under high temperature at the end of prograde metamorphism. Monazite compositions show negative Eu anomalies, which we interpret to be inherited from the source rock, not reflecting the coexistence with plagioclase and/or K-feldspar, which are unstable at UHP conditions. Our results suggest that the effect of whole-rock composition may be more important than that of coexisting phases. The UHP monazite was most probably formed from allanite during subduction and prograde metamorphism. The monazites included in garnet and kyanite are mostly unaltered, whereas those in the matrix show breakdown coronas consisting of apatite, REE-epidote/allanite and REE-carbonate, probably formed as a result of pressure decrease and cooling. U-Th-Pb chemical age dating of monazites yields an isochron centroid age of 472 +/- 3 Ma. We interpret this age as monazite growth under UHP conditions related to subduction of the Baltica continental margin in Early Ordovician time.