Resetting of the U-Pb zircon system in Cambro-Ordovician intrusives of the deep freeze range, Northern Victoria Land, Antarctica
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 gr...
| Published in: | Journal of Petrology |
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| Main Authors: | , , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
2007
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| Subjects: | |
| Online Access: | https://researchers.mq.edu.au/en/publications/f9304c7c-1802-4f98-89b0-5faf06312c9b https://doi.org/10.1093/petrology/egl064 http://www.scopus.com/inward/record.url?scp=34247217002&partnerID=8YFLogxK |
| Summary: | 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 ε 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. |
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