Contrasting Archaean crustal records in western part of the Napier Complex, East Antarctica: New constraints from SHRIMP geochronology

U-Pb zircon geochronology of 6 samples collected from Fyfe Hills (2 felsic orthogneisses and 1 quartzo-feldspathic gneiss) and Mt. Cronus (1 quartzo-feldspathic gneiss and 2 quartzites) in the western part of the Napier Complex, East Antarctica, revealed an Archaean-Proterozoic history ranging from 3128 to 1824 Ma. The absence of ancient evidence >3800-3600 Ma indicates that these ages were not always dominant in these two areas. The 3128-2580 Ma protolith ages are similar to those of other areas (e.g., Mt. Riiser-Larsen, Tonagh Island), while the magmatic protolith age of 2741 Ma obtained for the Fyfe Hills orthogneiss is a new component of the Archaean magmatic protolith in the Napier Complex. Metamorphic overgrowth or recrystallized zircons yielded systematic disconformable ages for both Fyfe Hills (>2518 Ma) and Mt. Cronus (similar to 2490 Ma). The presence of 2580 Ma inherited zircons provides important constraints that place the ultrahigh temperature metamorphic peak later than 2580 Ma. The post metamorphic ages suggest local fluid infiltration or local deformation event(s). (C) 2011 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.