U-Pb Age of Igneous and Metamorphic Events on the Fisher Massif (East Antarctica) and Its Significance for Geodynamic Reconstruction

摘要

This report presents the main results of LA-ICPMS studies of zircon from metamorphosed mag-matic rocks of the Fisher Massif in East Antarctica. The minimum age of crystallization for still unexplored granitoid intrusion in the southeastern part of the massif amounts to 1399 ± 11 Ma. The presence of inherited zircon of 1786 ± 23 Ma age in the rocks points to their fusion from a crustal source of Paleoproterozoic age. The time of the eruption of vulcanites of basite composition amounts to 1244 ± 11 Ma. The vulcanites contain xenogenic zircon of Late Archean and Middle Proterozoic age; hence, their initial melt interacted with the heterogeneous continental crust. The earliest metamorphism of the amphibolite facies proceeded 1213 ± 16 Ma ago, and was accompanied with intense shift deformations. The time of volcanism complies with the age of a large basite dike swarm in Vestfold Hills, intruded about 1250 Ma ago, which is associated with the destruction of the hypothetical Paleoproterozoic Nuna (Columbia) continent.