Synkinematic emplacement of lassiter coast intrusive suite plutons during the palmer land event: Evidence for mid-cretaceous sinistral transpression at the beaumont glacier in eastern palmer land

Alan P.M. Vaughan, Craig Storey, Simon P. Kelley, Tiffany L. Barry, Michael L. Curtis

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

New structural and geochronological data from the Eastern Palmer Land Shear Zone, in the vicinity of Beaumont Glacier, provide the first evidence of dated structural control on emplacement of the 119-95 Ma, >13000 km 2 Cretaceous Lassiter Coast Intrusive Suite, during the accretionary mid-Cretaceous Palmer Land Event orogeny. A previously undated >100 m thick dyke-like quartz tonalite intrusion was emplaced at 116.5 ± 1.5 Ma (Ar-Ar biotite cooling age) along a NW-SE axis, coeval with NW-SE compressional deformation, and possibly controlled by sinistral transpression along the Beaumont Glacier shear zone. The quartz tonalite preserves two styles of deformation and was probably progressively deformed by normal-sinistral shearing during magmatic cooling with initial deformation of mafic enclaves in the dyke interior and final formation of proto-mylonite to mylonite on the dyke margin. The quartz tonalite cuts folding associated with Phase 1 of the Palmer Land Event, indicating that this folding is older than 116 Ma, extending the onset of Phase 1 back in time. Mylonite on the quartz tonalite sheet margin was subsequently thermally reset at c. 107 Ma (Ar-Ar biotite method), during a peak in Lassiter Coast Intrusive Suite magmatism.

Original languageEnglish
Pages (from-to)759-771
Number of pages13
JournalJournal of the Geological Society
Volume169
Issue number6
DOIs
Publication statusPublished - 1 Nov 2012

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