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

摘要

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 (~. 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).