Analysis of dredged samples from the Gulden Draak Knoll demonstrates that it is a submarine rifted continental fragment that lies at the boundary between the western Perth Abyssal Plain and Wharton Basin, Indian Ocean. The Knoll comprises a granulite facies basement, including pelitic paragneiss and mafic orthogneiss, with a Cambrian granite inferred to intrude the other rocks. Boulders and cobbles of felsic gneiss with Mesoproterozoic and Cambrian protolith ages were also sampled likely reflecting a complex basement to variable sedimentary and volcanic rocks. The U–Pb isotopic system in the Archean and Mesoproterozoic zircon is significantly disturbed, reflecting Cambrian orogenesis that affected all samples. The protolith to garnet–sillimanite–biotite paragneiss has a maximum deposition age of 1163 ± 24 Ma and includes older detrital zircon grains with populations at c. 2.65 Ga and between 1.4 and 1.1 Ga. A younger population in this sample is interpreted as a mix of newly grown metamorphic zircon and isotopically reset zircon, implying that the granulite facies metamorphism occurred at c. 511 ± 5 Ma. Protracted Cambrian orogenesis is indicated by a metamorphic age in the mafic orthogneiss of 530 ± 6 Ma and isotopic disturbance shortly following emplacement of granite (c. 540 Ma with zircon ages disturbed to 509 ± 7 Ma) and the protolith to the felsic orthogneiss (c. 528 Ma with zircon ages disturbed to 510 ± 3 Ma). Xenocrystic zircon grains in the Cambrian rocks include Archean (c. 2839 ± 9 Ma) and Mesoproterozoic (1230–1370 Ma) populations also isotopically disturbed during Cambrian orogenesis. Igneous Cambrian zircon grains have less radiogenic Hf-isotope compositions (Hf_i = 0.281821–0.281367) than Mesoproterozoic xenocrysts (Hf_i = 0.282267–0.281993), indicating limited involvement of the Mesoproterozoic crust in granite production. A more likely source includes Archean crust represented by xenocrysts with Hf_i = 0.281399–0.280863. The Gulden Draak Knoll is reconstructed in Gondwana (‘Leeuwin’ full-fit model) along strike of a major structure termed the Indo–Australo–Antarctic Suture (IAAS), recently mapped from geophysical interpretations in Wilkes Land, Antarctica. New isotopic data suggest that basement rocks from the Gulden Draak Knoll have affinity to crust exposed either side of the IAAS. Determining if this structure is a suture zone sensu stricto remains to be tested.

Item Type:	Refereed Article
Keywords:	Gondwana, East Antarctica, Kuunga Orogen, zircon age, Hf-isotopes, reconstruction
Research Division:	Earth Sciences
Research Group:	Geology
Research Field:	Structural geology and tectonics
Objective Division:	Expanding Knowledge
Objective Group:	Expanding knowledge
Objective Field:	Expanding knowledge in the earth sciences
UTAS Author:	Halpin, JA (Dr Jacqueline Halpin)
UTAS Author:	Whittaker, JM (Associate Professor Jo Whittaker)
ID Code:	95969
Year Published:	2015 (online first 2014)
Web of Science® Times Cited:	28
Deposited By:	Centre for Ore Deposit Research - CODES CoE
Deposited On:	2014-10-13
Last Modified:	2017-10-31
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