Phanerozoic burial and unroofing history of the western Slave craton and Wopmay orogen from apatite (U–Th)/He thermochronometry
Introduction
Cratons are stable and relatively resistant to disruption, largely attributable to their cold, thick, chemically depleted lithospheric mantle roots (Jordan, 1978). Some cratonic regions, such as the interior of North America, have undergone repeated episodes of burial and unroofing as recorded by thick sequences of Phanerozoic strata interspersed with widespread unconformities (e.g., Sloss, 1963, Bond, 1978). Phases of denudation and aggradation may reflect low amplitude, long wavelength vertical cratonic motions, superimposed on the record of eustatic sea level change. These patterns may suggest a more dynamic history of cratonic regions than commonly recognized, possibly linked with deep-seated mantle and far-field plate boundary processes. For example, dynamic topography, or vertical displacement of the Earth's surface by up to several kilometers in response to mantle flow, has been invoked to explain low amplitude subsidence and uplift in some continental interiors (e.g., Mitrovica et al., 1989, Gurnis, 1993, Burgess et al., 1997, Pysklywec and Mitrovica, 1998, Pysklywec and Mitrovica, 2000). Most cratons are pierced by kimberlites and mafic dike swarms that were emplaced following craton stabilization, and reflect younger thermal and mechanical disruptions to the cratonic lithosphere that may be linked with burial and unroofing patterns at the surface. The discrete lithotectonic blocks of variable age and architecture that make up cratons could respond differently to these younger perturbations, manifested as differing depositional and erosional histories across a cratonic region.
The Archean Slave craton and adjacent Paleoproterozoic Wopmay orogen in the northwestern Canadian shield together present an excellent location in which to address these issues (Fig. 1). The Canadian shield is a vast cratonic region consisting of a collage of Archean cratons that were amalgamated in the Paleoproterozoic. The “Slave craton” is an Archean craton that was assimilated into the Canadian shield; “Wopmay orogen” is a Paleoproterozoic orogenic belt that was active in the assembly of the Canadian shield and ultimately became part of the larger cratonic region. The Slave craton has been extensively studied and was repeatedly disrupted by kimberlites in Phanerozoic time (e.g., Heaman et al., 2003). Although the craton currently lacks Phanerozoic cover, some kimberlites contain sedimentary xenoliths that record snapshots of the extent and, in some cases, the thicknesses of Phanerozoic strata across the region. We acquired apatite (U–Th)/He thermochronometry data along a southeast to northwest transect extending over 250 km from the interior of the Slave craton into the adjacent Wopmay orogen to more fully constrain the magnitude, extent, and timing of past burial and unroofing episodes, and to assess whether differential unroofing occurred across the Slave–Wopmay lithospheric boundary. If lithospheric architecture exerts a fundamental control on the lithospheric response to younger thermal and mechanical perturbations, then this would predict contrasts between the low temperature histories of Archean and Proterozoic terranes that were affected by such perturbations. We incorporate our thermochronological data with numerous geologic and stratigraphic constraints to decipher the burial and unroofing history of the northwestern Canadian shield. These results allow a preliminary assessment of potential relationships among phases of cratonic sedimentation and denudation, plate margin tectonism, and kimberlite generation and emplacement in the region.
Section snippets
Geologic setting
The Slave craton is a ~ 210,000 km2 region of > 4.0–2.55 Ga north-northeast striking tonalitic gneisses, plutonic and metavolcanic rocks, and metaturbidites (Fig. 1A; Isachsen and Bowring, 1994, Bowring and Williams, 1999, Davis et al., 2003). The craton is bounded by Proterozoic orogenic belts to the east, south, and west, and covered by younger (ca. 1.66 Ga) basinal sequences to the north (Bowring and Ross, 1985). Within the central Slave craton, Nd and Pb isotopic studies have been used to
Compilation of geologic constraints on the burial and unroofing history of the Slave craton
Geologic constraints on the burial and unroofing history of the western and central Slave craton and Wopmay orogen are numerous. Fourteen key constraints are summarized in Table 1, their locations are marked in Fig. 1A, and location numbers are noted in the text below. Five of these bear on the depth of the present day erosion surface during Proterozoic time. First, 40Ar/39Ar biotite dates from Archean plutonic rocks of the Yellowknife domain indicate that the Archean basement cooled through ~
Apatite (U–Th)/He thermochronometry
Apatite (U–Th)/He thermochronometry is conventionally assumed to be sensitive to temperatures from ~ 70 to 30 °C (Farley, 2000). Recent studies demonstrated that the accumulation of radiation damage increases the apatite He retentivity, and that the elimination of damage reduces it (Shuster et al., 2006, Shuster and Farley, 2009). With sufficient time at the low temperatures required for radiation damage accumulation, an apatite with higher [eU] (effective U concentration, which weights the
Low temperature history of the northwestern Canadian shield
The geologic constraints (Table 1) suggest that the dominant phase of Phanerozoic burial of the Slave craton and Wopmay orogen occurred between Cambrian and Jurassic time, with an ancillary phase of burial in the Cretaceous and Early Tertiary. We integrate this information with our new apatite (U–Th)/He data (Table 2) to further decipher the details of this history. Specifically, the data can better resolve: 1) the minimum peak temperature and associated burial depth during the
Conclusions
New apatite (U–Th)/He data from the western Slave craton and Wopmay orogen yield mean dates of 296 to 242 Ma and 231 to 212 Ma, respectively. The younger dates from Wopmay orogen, although statistically indistinguishable from the Slave craton results, may be due to higher heat flow or slightly younger unroofing in the western portion of the sample transect. These data, when combined with geologic and stratigraphic information, imply that the apatites experienced complete He loss in
Acknowledgements
This worked was supported by National Science Foundation grant EAR-0711451 to RMF and SAB, and a National Science Foundation graduate research fellowship and Spetzler Scholarship to AKA. Many of the samples come from the joint fieldwork of R.S. Hildebrand and SAB. We thank Rich Ketcham and an anonymous reviewer for thorough and insightful comments that improved the clarity of the manuscript.
References (80)
- et al.
Assembling and reactivating the Proterozoic Capricorn orogen: lithotectonic elements, orogenies, and significance
Precambrian Res.
(2004) - et al.
Kimberlites: their relation to mantle hotspots
Earth Planet. Sci. Lett.
(1980) - et al.
Lithosphere development in the Slave craton: a linked crustal and mantle perspective
Lithos
(2003) - et al.
The effects of long alpha-stopping distances on (U–Th)/He ages
Geochim. Cosmochim. Acta
(1996) Exploiting radiation damage control on apatite (U–Th)/He dates in cratonic regions
Earth Planet. Sci. Lett.
(2009)Superkimberlites: a geodynamic diamond window to the Earth's core
Earth Planet. Sci. Lett.
(1994)- et al.
The timing of kimberlite magmatism in North America: implications for global kimberlite genesis and diamond exploration
Lithos
(2003) - et al.
Tectono-magmatic evolution of the 1.9 Ga Great Bear magmatic zone, Wopmay orogen, northwestern Canada
J. Volcanol. Geotherm. Res.
(1987) - et al.
Mackenzie igneous event, Canada: Middle Proterozoic hotspot magmatism associated with ocean opening
Earth Planet. Sci. Lett.
(1989) - et al.
Influence of terrain on bedrock temperatures
Glob. Planet. Change
(1992)
Combined apatite fission track and (U–Th)/He thermochronometry in a slowly cooled terrane: results from a 3440-m-deep drill hole in the southern Canadian shield
Earth Planet. Sci. Lett.
Thermal history of the Williston Basin from apatite fission-track thermochronometry—implications for petroleum systems and geodynamic history
Tectonophysics
Thermal structure, thickness and composition of continental lithosphere
Chem. Geol.
A plate tectonic origin for diamond-bearing kimberlites
Earth Planet. Sci. Lett.
The influence of artificial radiation damage and thermal annealing on helium diffusion kinetics in apatite
Geochim. Cosmochim. Acta
The influence of natural radiation damage on helium diffusion kinetics in apatite
Earth Planet. Sci. Lett.
Reconstruction of burial history of eroded Mesozoic strata using kimberlite shale xenoliths, volcaniclastic and crater facies, Northwest Territories, Canada
Int. J. Coal Geol.
Evidence for simultaneous contraction and extension at different crustal levels during the Caledonian orogeny in NE Greenland
J. Geol. Soc. (Lond.)
Structure, seismic data, and orogenic evolution of the southern Canadian Rockies
Bull. Can. Pet. Geol.
Longitudinal petrochemical variation in the Mackenzie Dyke swarm, northwestern Canadian Shield
J. Petrol.
Laser 40Ar/39Ar thermochronology of Archean rocks in Yellowknife Domain, southwestern Slave Province: insights into the cooling history of an Archean granite–greenstone terrane
Can. J. Earth Sci.
Speculations of real sea-level changes and vertical motions of continents at selected times in the Cretaceous and Tertiary periods
Geology
Geochronology of the Narakay volcanic complex: implications for the age of the Coppermine Homocline and Mackenzie igneous events
Can. J. Earth Sci.
Growth, stabilization, and reactivation of Proterozoic lithosphere in the southwestern United States
Geology
Implications of new chronostratigraphy for tectonic evolution of Wopmay orogen, Northwest Canadian Shield
Am. J. Sci.
Priscoan (4.00–4.03 Ga) orthogneisses from northwestern Canada
Contrib. Mineral. Petrol.
Formation of sequences in the cratonic interior of North America by interaction between mantle, eustatic, and stratigraphic processes
GSA Bull.
Canada's craton: a bottoms-up view
GSA Today
Thermal gradients in the continental crust
Remnants of Paleozoic cover on the Archean Canadian Shield: limestone xenoliths from kimberlite in the central Slave craton
Geology
Neodymium isotopic evidence for the accretionary development of the Late Archean Slave Province
Contrib. Mineral. Petrol.
Evolution of the North American Cordillera
Annu. Rev. Earth Planet. Sci.
Isopach and structure contour maps of Mesozoic to Tertiary strata in the northern Interior Plains, N.W.T. Open File 3150
Evolution of the Precambrian lithosphere: seismological and geochemical constraints
J. Geophys. Res.
Helium diffusion from apatite: general behavior as illustrated by Durango fluorapatite
J. Geophys. Res.
Radiation damage control on apatite (U–Th)/He dates from the Grand Canyon region, Colorado Plateau
Geology
Rejuvenation and erosion of the cratonic lithosphere
Nat. Geosci.
Phanerozoic marine inundation of continents driven by dynamic topography above subducting slabs
Nature
Petroleum potential of the Cambrian Mount Clarke Formation (Tedji Lake Play), Colville Hills area, Northwest Territories
Cited by (52)
Investigating apatite (U-Th)/He thermochronologic ages to understand exhumation history of the Ethiopian Plateau
2023, Journal of African Earth SciencesThe post-Caledonian thermo-tectonic evolution of Fennoscandia
2022, Gondwana Research(U-Th)/He Chronology
2020, Encyclopedia of Geology: Volume 1-6, Second Edition