Vp. Kovach et al., Age limits of high-grade metamorphic supracrustal complexes in the centralAldan Shield: Sm-Nd isotopic data, STRATI GEOL, 7(1), 1999, pp. 1-14
First investigation results on Sm-Nd isotope systems in elastic metasedimen
tary and metavolcanic rocks from the high-grade metamorphic supracrustal co
mplexes of central Aldan Shield are used to approximately evaluate their ma
ximum age boundary. It is established that the Upper Archean rocks (model a
ge T-Nd(DM) = 3.3-2.6 Ga) served as a principal source material for metapel
ites of the Kurumkan Group; metapelites and metagraywackes of the Amedichi
Group; and also for the metagraywackes of the Kurulta, Zverev, and Seim gro
ups. Provenances with the Early Archean model age (TNd(DM)= 3.5 Ga) are fou
nd to be appropriate only for few rock samples from the Kurumkan and Kurult
a groups. The Early Proterozoic age (T-Nd(DM) = 2.5-2.2 Ga) is inferred for
the protolith material of supracrustal rocks of the Chuga, Kholbolokh, Kyu
rikan, Idzhek, and Fedorov groups. The data obtained suggest that supracrus
tal rocks of the Aldan granulite-gneiss and East Olekma granite-greenstone
terranes were formed not in the Early Archean, as it was formerly believed,
but at the Late Archean and/or Early Proterozoic stages of geologic evolut
ion of the shield.