Thursday, 30 August 2007
4.PS-97
New evidences for the early Archaean evolution of Aker Peaks, Napier Mountains, Enderby Land (East Antarctica)
Boris V. Belyatsky1, Nickolay V. Rodionov2, Sergey A. Sergeev2, German L. Leitchenkov1, and Eugene N. Kamenev1. (1) Department of Antarctic Geology, VNIIOkeangeologia, Angliisky str., 1, St.-Petersburg, Russia, (2) CIR, VSEGEI, Sredniy ave., 74, St.Petersburg, 199106, Russia
Zircons from charnockite-enderbite rocks (Aker Peaks, Napier Mountains), which we have dated by SHRIMP-II, were analyzed earlier by conventional multigrain U-Pb ID-TIMS methods (Belyatsky et al., 1990) but gave equivocal ages. Our study demonstrates that the most optimal way to evaluate geologic events in such rocks is by ion-probe analysis of complex zircons (CL, BSE, REE composition). We have obtained, for the first time, reliable ages of magmatic crystallization for studied charnockite-enderbites (3620 ± 30 Ma) and the age of the primary enderbite's protolith origin (3950-3970 Ma). Moreover, in all dated zircons a metamorphic event of 2450-2480 Ma is clearly recorded and is in agreement with the granulite-facies metamorphism described by many authors. These conclusions coincide well with Sm-Nd isotope data for these enderbite-charnockite gneisses.