TY - JOUR N2 - The Blue Dyke and Jardine Peak are subvertical hypabyssal intrusions cutting a stratiform volcanic sequence in the Admiralty Bay area on King George Island (South Shetlands, Antarctica ). The rocks are porphyritic, crystal-rich basaltic andesites. Tiny zircon crystals were used for single grain SHRIMP U-Pb dating. The mean ages calculated for the zircon populations from both intrusions indicates Late Oligocene (Chattian) formations. Zircon grains from the Blue Dyke gave the mean age of 27.9±0.3 Ma, whereas those from the Jardine Peak are slightly younger displaying the mean age of 25.4 ± 0.4 Ma: a Late Oligocene (Chattian) crystallization age the inferred of both these intrusions. These are much younger than previous Eocene K-Ar and Ar-Ar ages for such rocks and suggest that formation of the King George Island intrusions can be related to tectonic processes that accompanied the opening of the Drake Passage. L1 - http://www.czasopisma.pan.pl/Content/110559/PDF/PPR30-379.pdf L2 - http://www.czasopisma.pan.pl/Content/110559 PY - 2009 IS - No 4 EP - 391 KW - Antarctica KW - King George Island KW - Late Oligocene KW - U-Pb SHRIMP dating A1 - Pańczyk, Magdalena A1 - Nawrocki, Jerzy A1 - Williams, Ian S. PB - Polish Academy of Sciences PB - Committee on Polar Research VL - vol. 30 DA - 2009 T1 - Isotope age constraint for the Blue Dyke and Jardine Peak subvertical intrusions of King George Island , West Antarctica SP - 379 UR - http://www.czasopisma.pan.pl/dlibra/publication/edition/110559 T2 - Polish Polar Research ER -