Sr-Nd isotopic composition of lamprophyre dykes from Queen Maud Land, EastAntarctica

Alkali basaltic-lamprophyric dykes intrude Precambrian gneisses in the Schi rmacher Oasis, Queen Maud Land, East Antarctica. Rb-Sr and sm-Nd isotopic d ata on two lamprophyre dykes are reported from the Schirmacher Oasis. The l amprophyre dykes have given Rb-Sr biotite/whole rock isochron age of 439 +/ - 10 Ma (2 sigma). Large variations in epsilon Sr and epsilon Nd indicate h igher degree of crustal assimilation. Higher epsilon Sr (+54 to +72) and lo wer epsilon Nd (-7 to -13) of these dykes also suggest that the source was contaminated by older crust. Biotite/whole rock Rb-Sr isotope data on lampr ophyre dykes show that the terrain was affected by thermal event during ear ly Paleozoic which is correlated with the end of Pan-African orogeny.