Precambrian Research 135 (2004) 149–176 Evolution of an Archean basement complex and its autochthonous cover, southern Slave Province, Canada John W.F. Ketchum a,∗ , Wouter Bleeker b , Richard A. Stern b,1 a Jack Satterly Geochronology Laboratory, Royal Ontario Museum, 100 Queen’s Park, Toronto, Ontario, Canada M5S 2C6 b Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario, Canada K1A 0E8 Received 24 July 2003; accepted 25 August 2004 Abstract The Sleepy Dragon Complex (SDC) is one of several antiformal exposures of a 4.0–2.85 Ga basement block underlying the west-central region of the Archean Slave Province, northwestern Canada. This basement block, the Central Slave Basement Complex (CSBC), is overlain by an autochthonous to locally parautochthonous, dominantly quartz-rich clastic sequence, the 2.85–2.80Ga Central Slave Cover Group. Together these units comprised a fundamental building block during Neoarchean growth and assembly of the Slave craton. The well-exposed Patterson Lake–Morose Lake area represents a type locality for study of the CSBC, Central Slave Cover Group, and overlying rocks of the Yellowknife Supergroup. Field mapping and U–Pb geochronology, employing both thermal ionisation mass spectrometry (TIMS) and sensitive high resolution ion microprobe (SHRIMP), document a prolonged crustal history. Oldest intact basement units consist of foliated to gneissic tonalite dated in two places at 2955 ± 12 Ma and 2944 ± 9 Ma. Indirect evidence for a ca. 3150 Ma basement component is obtained both from xenocrystic zircon in tonalite and detrital zircons from the overlying Central Slave Cover Group, which here consists of the Patterson Lake Formation. A granite boulder from this formation is dated at 2934 ± 3 Ma and may be locally derived. A sheared mafic volcanic unit along the basement-cover contact contains 2942 ± 3 Ma metamorphic titanite which provides a minimum deposition age. This volcanic unit is therefore also a part of the basement complex. Younger events in the SDC mainly reflect tonalite-trondhjemite-granodiorite plutonism during construction of the overlying Cameron River and Beaulieu River greenstone belts of the Yellowknife Supergroup. A unit of K-feldspar megacrystic granodiorite is dated at 2726 ± 3 Ma, and tonalite and granodiorite bodies located toward the centre of the SDC have primary crystallization ages of 2683 + 3/-2 Ma, 2677 ± 2 Ma, and 2672 + 7/-6 Ma. The core of the southern SDC is occupied by a late-tectonic to post-tectonic granite pluton previously dated at 2586 ± 2 Ma. An intravolcanic unconformity along the southern margin of the SDC (developed in part on 2.7 Ga granodiorite) is constrained by existing U–Pb data to have formed sometime between ∗ Corresponding author. Present address: GEMOC ARC National Key Centre, Department of Earth and Planetary Sciences, Macquarie University, New South Wales 2109, Australia. Fax: +612 9850 8943. E-mail address: jketchum@els.mq.edu.au (J.W.F. Ketchum). 1 Present address: Centre for Microscopy and Microanalysis, M010, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia. 0301-9268/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.precamres.2004.08.005