New evidence for the early Archean evolution of Aker Peaks, Napier Mountains

• Main Authors: Enderby L, East Antarctica
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Aker Peaks; Napier; Napier Mountains
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.578.967; http://pubs.usgs.gov/of/2007/1047/ea/of2007-1047ea187.pdf

Summary 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. This study shows that the optimal way to evaluate geologic events in such rocks is local ion-probe analysis of complex zircons with preliminary study of CL, BSE, REE patterns. Due to this approach 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 (3950 – 3970 Ma). Moreover, in all dated zircons a metamorphic event of 2450 – 2480 Ma is clearly recorded that is in agreement with the granulite-facies metamorphism described by many authors. These conclusions coincide well with our Sm-Nd isotope data for these enderbite-charnockite gneisses.