Paleoproterozoic intracratonic basin processes, from breakup of Kenorland to assembly of Laurentia: Hurwitz Basin, Nunavut, Canada

The evolution of Hurwitz Basin records discontinuous tectonic processes in the Hearne domain (northern Canada) resulting from changing distant boundar y conditions. Magmatic, eustatic and paleoclimatic influences, although sig nificant, are considered to have been of secondary importance. In agreement with recent models, lower Hurwitz Group units record intracratonic basin f ormation during initial breakup stages of a speculative Neoarchean supercon tinent (Kenorland). In contrast to recent models, new Sm-Nd and Pb-Pb data and recent detrital zircon geochronology document a hitherto unsuspected ti me break (at least 200 My) within the Hurwitz Group (ca. 2.11-1.91 Ga). The se data indicate that the deposition of upper Hurwitz Group units overlappe d with ca. 2.0-1.7 Ga amalgamation of the Slave, Superior, Sask, Wyoming an d Nain cratons during assembly of Laurentia. Initiation of Hurwitz Basin an d deposition of predominantly continental siliciclastic rocks in sequence 1 (Noomut, Padlei and Kinga Formations) were due to regional sagging in resp onse to early lithospheric stretching. Immature deep-water pelites of seque nce 2 (Ameto Formation) reflect basin-margin arching and basin-centered dee pening related to a second episode of stretching. Gabbro sills and dykes (2 .11 Ga), emplaced after lithification of the Ameto Formation represent cont inued stretching that ultimately led to dispersion of Kenorland's daughter fragments. The gap in the sedimentary record signifies a time when processe s required to generate permanent subsidence were lacking. Mixed siliciclast ic-carbonate ramp and fluvial deposits of sequences 3 and 4 (Watterson, Duc ker and Tavani Formations) were deposited after ca. 1.91 Ga, during shorten ing from the west (related to Taltson-Thelon and Wopmay orogens), but bound ary conditions to the south are less certain. These may have involved eithe r extension related to late fragmentation and dispersion of the southern He arne margin, or shortening due to early (ca. 1.87 Ga) collisional processes in western Trans-Hudson orogen. Similar to the classic Phanerozoic intracr atonic basins of North America, we infer that tectonic subsidence in Hurwit z Basin is a reflection of plate tectonics, reinforcing similarities in bas in-forming processes between the early Paleoproterozoic and the Phanerozoic . (C) 2001 Elsevier Science B.V. All rights reserved.