U–Pb zircon ages and field relationships of Archean basement and Proterozoic intrusions, south-central Wopmay Orogen, NWT: implications for tectonic assignments

Abstract

New field and U–Pb zircon data from the south-central Wopmay Orogen (south of 65°N) establish crystallization ages of basement and plutonic phases and bring to the forefront questions on the architecture of the orogen. The complex and extensive >3300–2575 Ma basement domain was derived from the adjacent Slave craton. Paleoproterozoic supracrustal rocks, dominated by an extensive pelitic–psammitic sequence with basal arenite, conglomerate, and carbonate, unconformably overlie this basement. Pre- to post-kinematic Paleoproterozoic plutons intrude both basement and overlying strata and crystallized at 1877, 1867–1862, and 1858–1850 Ma. The first pulse of plutonism constrains an early generation of metamorphism and deformation to younger than 1877 Ma and is corroborated by metamorphic zircon in Archean basement. The interval from 1867 to 1862 Ma brackets ductile deformation in granite and granodiorite intrusions; although corresponding structure in the metasedimentary strata is equivocal. Post-kinematic ca. 1858–1850 Ma plutons were coeval with localized high-grade metamorphism and concomitant recrystallization of Archean basement. The absence of older (>1880 Ma) phases of the Hepburn intrusive suite in south-central Wopmay Orogen demonstrates a previously unrecognized north–south plutonic dichotomy and that the historical assignment of Calderian metamorphism to ca. 1885 Ma may be too old. The designation of part of the area to a klippe of Hottah terrane is not compatible with field and zircon age data which shows that basement and the overlying strata can be tied directly to the Slave craton. The study raises questions regarding the tectonic relationship between the Hottah terrane and Slave craton.

Chronostratigraphy of the Hottah terrane and Great Bear magmatic zone of Wopmay Orogen, Canada, and exploration of a terrane translation model

“…1, 2;Fraser et al 1972;Badham 1973;Hoffman 1973Hoffman , 1980Hoffman , 1984Hoffman , 1988aHoffman and McGlynn 1977;Hoffman et al 1976;King 1986, 1987;Villeneuve et al 1991Villeneuve et al , 1993Aspler et al 2003;Cook and Erdmer 2005;Jackson 2008;Hildebrand et al 1987aHildebrand et al , 1987bHildebrand et al , 2010aHildebrand et al , 2010bJackson and Ootes 2012;Jackson et al 2013;Ootes et al 2013). The Coronation margin includes Archean crust, the ca.…”

“…2.014 Ga Melville Group rift-to-drift sequence, the 1.97 Ga Epworth Group passive margin sedimentary rocks, and the ca. 1.88 Ga Recluse Group foredeep sedimentary rocks preserved in the east-verging Asiak thrust-fold belt, as well as correlatives preserved as supracrustal, gneissic, and intrusive rocks in the metamorphic internal zone (Hoffman 1973(Hoffman , 1980(Hoffman , 1984King 1986, 1987;Bowring and Grotzinger 1992;Hoffman et al 2011;Jackson et al 2013). The Wopmay fault zone is a north-south-striking crustal-scale fault that delimits the western extent of exposed Archean rocks in the Wopmay Orogen (Figs.…”

“…The Wopmay fault zone is a north-south-striking crustal-scale fault that delimits the western extent of exposed Archean rocks in the Wopmay Orogen (Figs. 1, 2;St-Onge et al 1983;King 1986;Bowring and Podosek 1989;Housh et al 1989;Jackson 2008;Jackson et al 2006Jackson et al , 2013Spratt et al 2009;Jackson and Ootes 2012: also called medial zone by Hildebrand et al 1991Hildebrand et al , 2010a. West of Wopmay fault zone are the remnants of the >1.9 Ga Hottah terrane, which was extensively overprinted by ca.…”

“…Bedrock mapping and U-Pb zircon geochronology of Archean basement in the metamorphic internal zone of the Wopmay Orogen and bedrock mapping in the vicinity of Hottah Lake have raised a number of questions about the previously ascribed relationship of the Slave craton and Hottah terrane (Jackson and Ootes 2012;Jackson et al 2013). For this study we collected and dated key volcanic and plutonic units within the central area of the Wopmay Orogen, mostly between 64°N and 65°N (Fig.…”

“…The Hottah terrane figures prominently in proposed evolutionary models for the Wopmay Orogen, and it was recognized early on that understanding the Hottah terrane was key to deciphering the Wopmay Orogen (Hoffman 1973;McGlynn 1976McGlynn , 1979Hoffman and McGlynn 1977;Hildebrand 1981). Forty years later, while new evidence continues to accumulate regarding the development of the Wopmay Orogen (e.g., Hoffman et al 2011;Jackson et al 2013), details regarding the evolution of the Hottah terrane remain sparse (Bowring 1984). Presented herein are new high-precision U-Pb zircon ages from the Hottah terrane and select volcanic horizons in the central Great Bear magmatic zone, complemented with trace-element and Nd-isotope data.…”