subvertical intrusions of King George Island

• Main Authors: Jardine Peak, Magdalena Pańczyk, Jerzy Nawrocki, Ian S. Williams
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Key words; Antarctica; King George Island; Late Oligocene; U−Pb SHRIMP dating; Admiralty Bay; Blue Dyke; Drake Passage; Jardine Peak; Antarc*
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.625.7611; http://www.polar.pan.pl/ppr30/PPR30-379.pdf

Abstract: 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.