Australian Journal of Earth Sciences (2004) 51, 645–664 U–Pb zircon geochronology of Late Devonian to Early Carboniferous extension-related silicic volcanism in the northern New England Fold Belt* S. E. BRYAN, 1† C. M. ALLEN, 2 R. J. HOLCOMBE 1 AND C. R. FIELDING 1‡ 1 Department of Earth Sciences, University of Queensland, Qld 4072, Australia. 2 Research School of Earth Sciences, Australian National University, ACT 0200, Australia. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis of zircons confirm a Late Devonian to Early Carboniferous age (ca 360–350 Ma) for silicic volcanic rocks of the Campwyn Volcanics and Yarrol terrane of the northern New England Fold Belt (Queensland). These rocks are coeval with silicic volcanism recorded elsewhere in the fold belt at this time (Connors Arch, Drummond Basin). The new U–Pb zircon ages, in combination with those from previous studies, show that silicic magmatism was both widespread across the northern New England Fold Belt (>250 000 km 2 and 500 km inboard of plate margin) and protracted, occurring over a period of ~15 million years. Zircon inheritance is commonplace in the Late Devonian – Early Carboniferous volcanics, reflecting anatectic melting and considerable reworking of continental crust. Inherited zircon components range from ca 370 to ca 2050 Ma, with Middle Devonian (385–370 Ma) zircons being common to almost all dated units. Precambrian zircon components record either Precambrian crystalline crust or sedimentary accumulations that were present above or within the zone of magma formation. This contrasts with a lack of significant zircon inheritance in younger Permo-Carboniferous igneous rocks intruded through, and emplaced on top of, the Devonian–Carboniferous successions. The inheritance data and location of these volcanic rocks at the eastern margins of the northern New England Fold Belt, coupled with Sr–Nd, Pb isotopic data and depleted mantle model ages for Late Palaeozoic and Mesozoic magmatism, imply that Precambrian mafic and felsic crustal materials (potentially as old as 2050 Ma), or at the very least Lower Palaeozoic rocks derived from the reworking of Precambrian rocks, comprise basement to the eastern parts of the fold belt. This crustal basement architecture may be a relict from the Late Proterozoic breakup of the Rodinian supercontinent. KEY WORDS: Carboniferous, crustal reworking, Devonian, inheritance, New England Fold Belt, uranium–lead dating, zircon. INTRODUCTION The Late Devonian to Early Carboniferous (ca 360–340 Ma) is one of several periods in the Palaeozoic and Mesozoic in which silicic magmatism occurred across the northern New England Fold Belt of Queensland. However, many igneous rocks previously assumed to be Devonian and Early Carboniferous in age are now known from recent studies to be distinctly younger (mostly Late Carbon- iferous – Early Permian: Allen et al. 1998). These igneous rocks had been interpreted as supra-subduction zone magmatic – arc rocks and therefore provided an important reference frame for tectonic models of the fold belt (Day et al. 1978; Murray et al. 1987). Relatively limited geochronological data have consequently required that age constraints for the Devonian–Carboniferous tectonic elements of the northern New England Fold Belt be based upon biostratigraphic data (Jensen et al. 1966; Dear et al. 1971; Roberts & Engel 1980; Yarrol Project Team 1997). We present U–Pb geochronological data for silicic volcanic and intrusive rocks from the Upper Devonian to Lower Carboniferous Campwyn Volcanics and correlative formations (Mt Alma Formation and Rockhampton Group) of the Yarrol terrane along-strike to the south in the northern New England Fold Belt (Figure 1). The new data complement stratigraphic and facies analysis studies of the Yarrol terrane (Bryan et al. 2001) and Campwyn Volcanics (Bryan et al. 2003a). These data are used to constrain the Devonian–Carboniferous silicic magmatic history of the northern New England Fold Belt, particu- larly the timing of the transition from mafic to silicic magmatism (Bryan et al. 2001, 2003a). This transition is also recognised near the Devonian–Carboniferous bound- ary in the southern New England Fold Belt (Leitch 1974). The new data further indicate that silicic volcanics from the Campwyn Volcanics and Yarrol terrane are contem- poraneous with silicic volcanism that occurred elsewhere *Appendix 1 [indicated by an asterisk (*) in the text and listed at the end of the paper] is a Supplementary Paper; copies may be obtained from the Geological Society of Australia’s website (http://www.gsa.org.au) or from the National Library of Australia’s Pandora archive (http://nla.gov.au/nla.arc-25194). † Corresponding author and present address: Geology & Geophysics Department, Yale University, PO Box 208109, New Haven, CT 06520–8109, USA (scott.bryan@yale.edu). ‡ Present address: Department of Geosciences, University of Nebraska, 214 Bessey Hall, Lincoln, NE 68588–0340, USA.