Archean crustal evolution in the northern Yilgam Craton: U-Pb and Hf-isotope evidence from detrital zircons

The integrated application of U-Pb dating, Hf-isotope analysis and trace-element analysis to detrital zircon populations offers a rapid means of assessing the geochronology and crustal evolution history of different terranes within a composite craton. In situ U-Pb and Hf-isotope analyses of 550 zircons from 21 modem drainages across the northern part of the Yilgarn Craton and the adjacent Capricorn Orogen provide a broad view of crustal evolution in Archean and Proterozoic time. The oldest crustal components (3.7 Ga) are identified in the Yeelirrie geophysical domain [A.J. Whitaker, Proceedings of Fourth International Archaean Symposium Ext. Abstracts AGSO-Geoscience Australia Record, vol. 37, 2001, p. 536] that runs N-S down the middle of the craton; these components are represented by ancient zircons and also are reflected in the Hf model ages of younger magmas. Ancient (>3.4 Ga) crust contributed to the generation of younger magmas in the Narryer Province, and the proportion of ancient recycled material increases from east to west across the Murchison Province. In contrast, the Hf-isotope data provide no evidence for crust older than 2.9-3.0 Ga in the Southern Cross or Eastern Goldfields (including the Marymia Inlier) domains. The Yeelirrie domain and the composite Narryer-Murchison block are interpreted as ancient microcontinents, sandwiched with the juvenile terranes of the Southern Cross and Eastern Goldfields domains. There is little evidence for the existence of a Depleted Mantle reservoir beneath the Yilgarn Craton prior to 3.1-3.2 Ga, but this reservoir is a major contributor to crustal generation from 3.1 to 2.6 Ga; this suggests that much of the continental crust in the craton was generated after ca. 3.2 Ga. 1.8-2.3 Ga magmatism, associated with the Capricorn Orogen, involved the recycling of older crust with little obvious contribution from the Depleted Mantle. A significant (and previously unrecognised) 540 Ma episode in the NE part of the craton involved metamorphism or remelting of the 2.7-3.0 Ga crust of the Eastern Goldfields Province. (C) 2004 Elsevier B.V. All rights reserved.