Journal of Petrology Advance Access published online on November 21, 2006
Journal of Petrology, doi:10.1093/petrology/egl064
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Resetting of the U–Pb Zircon System in Cambro-Ordovician Intrusives of the Deep Freeze Range, Northern Victoria Land, Antarctica
1Dipartimento Di Scienze Della Terra, Università Di Siena, 53100 siena, Italy
2Gemoc Arc National Key Centre, Department of Earth and Planetary Sciences, Macquarie University, Sydney, Nsw 2109, Australia
Received February 25, 2005; Revised typescript accepted September 29, 2006
 |
Abstract |
|---|
A detailed in situ isotopic (U–Pb, Lu–Hf) and geochemical study of zircon populations in a composite sequence of foliated to massive Cambro-Ordovician intrusions in the Deep Freeze Range (North Victoria Land, Antarctica), has highlighted great complexity in zircon systematics. Zircons in deformed granitoids and tonalites display complex internal textures, a wide spread of concordant U–Pb ages (between 522 and 435 Ma) and unusual trace-element compositions (anomalous enrichment of light rare earth elements, U, Th and Y) within single zircon grains. In contrast, zircons from undeformed samples display a limited range of U–Pb ages and trace-element compositions. Zircons from all age and textural populations in most of the deformed and undeformed samples show a relatively narrow range of 
Hf values, suggesting that the Lu–Hf system remained undisturbed. Inferred emplacement ages cover a time interval of about 30 Myr: from 508 to 493 Ma for the oldest strongly foliated synkinematic Howard Peaks megacrystic monzogranites and high-K calc-alkaline mafic to intermediate rocks of the ‘Corner Tonalite’ unit; from about 489 to 481 Ma for the younger massive shoshonitic mafic dyke suite and the high-K calc-alkaline Keinath granite. The observed isotopic and chemical variations in zircon are attributed to a sub-solidus recrystallization under hydrous conditions and varying temperature, in a setting characterized by a transpressional to extensional stress regime.
KEY WORDS: Antarctica; Cambro-Ordovician intrusives; Ross Orogen; zircon U–Pb geochronology
*Corresponding author. +39-0577233970. +39-0577233938. bomparola{at}unisi.it
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  L. Bracciali, G. Di Vincenzo, S. Rocchi, and C. Ghezzo The Tiger Gabbro from northern Victoria Land, Antarctica: the roots of an island arc within the early Palaeozoic margin of Gondwana Journal of the Geological Society, July 1, 2009; 166(4): 711 - 724. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Rocchi, G. Di Vincenzo, C. Ghezzo, and I. Nardini Granite-lamprophyre connection in the latest stages of the early Paleozoic Ross Orogeny (Victoria Land, Antarctica) Geological Society of America Bulletin, May 1, 2009; 121(5-6): 801 - 819. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Tiepolo and R. Tribuzio Petrology and U-Pb Zircon Geochronology of Amphibole-rich Cumulates with Sanukitic Affinity from Husky Ridge (Northern Victoria Land, Antarctica): Insights into the Role of Amphibole in the Petrogenesis of Subduction-related Magmas J. Petrology, May 1, 2008; 49(5): 937 - 970. [Abstract] [Full Text] [PDF]
|
|