Abstract
40Ar/39Ar mineral ages have been determined from basement gneisses and cover sequences exposed in the Caledonides of North-East Greenland. These range between c. 438 Ma and c. 370 Ma (Early Silurian – Middle Devonian). They are interpreted as dating cooling folIowing polyphase Caledonian metamorphism which completely rejuvenated intracrystalline argon systems within the (early Proterozoic) basement gneisses. The 40Ar/39Ar results indicate that thrust-related regional deformation.
Highlights
4()ArP9Ar mineral ages have been determined from basement gneisses and cover sequences exposed in the Caledonides of North-East Greenland
AmphiboLe and muscovite from various lithologic units within the North-East Greenland Caledonides have been anaLysed using 4OArf39Ar incrementalreLease dating techniques to provide constraints on the timing of tectonothermal events, and in particular to establish an upper limit for regional deformation and metamorphism
The reliability of K-Ar mineral ages obtained by conventional methods is difficult to assess, because such ages may result from partial isotopic disturbance or excess argon
Summary
""AIpoAr apparent age spectrum of a muscovite concentrate from cleaved Trekant metasandstone within the Caledonian thrust zone exposed at Garde Nunatak (Iocation shown in Fig. l) (from Dallmeyer et al, 1994). Methods of York (1969). LS23 7BQ, U.K., and the Geological Society of London Library. Signiticant results are displayed as age spectra in Pigs 2-7. Most of the hornblende concentrates display slightly discordant 4°Arp9Ar age spectra in which variable apparent ages are tN
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