Isotope age constraint for the Blue Dyke and Jardine Peak subvertical intrusions of King George Island, West Antarctica

• Published in: Polish Polar Research
• Main Authors: Pańczyk, Magdalena, Nawrocki, Jerzy, Williams, Ian S.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Polska Akademia Nauk (Polish Academy of Sciences)
• Subjects: Antarctica; King George Island; Late Oligocene; U−Pb SHRIMP dating; West Antarctica; Drake Passage; Admiralty Bay; Blue Dyke; Jardine Peak; Antarc*; Polar Research
• Online Access: http://hdl.handle.net/1885/104124; https://doi.org/10.4202/ppres.2009.20; https://openresearch-repository.anu.edu.au/bitstream/1885/104124/4/01_PA%C5%83CZYK_Isotope_age_constraint_for_the_2009.pdf.jpg

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 zir− con 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 ac− companied the opening of the Drake Passage.