Phanerozoic surface history of the Slave craton

Abstract

[1] New apatite (U-Th)/He (AHe) thermochronometry data and key geologic constraints from Slave craton kimberlites are used to develop a model for the Phanerozoic burial, unroofing, and hypsometric history of the northwestern Canadian shield. AHe dates range from 210 ± 13 to 382 ± 79 Ma, are older in the eastern Slave craton and decrease westward, and resolve the spatial extent, thickness, and history of now-denuded sedimentary units. Results indicate Paleozoic heating to temperatures ≥85-90°C, suggesting regional burial beneath ≥2.8 km of strata while the region was at sea level, followed by the westward migration of unroofing across the craton. This Paleozoic-Mesozoic history does not correlate with sea level change, instead requiring Paleozoic subsidence of the craton followed by surface uplift. The AHe data restrict Cretaceous burial to ≤1.6 km, followed by unroofing, Eocene terrestrial sediment deposition, and removal of Phanerozoic sedimentary cover across the region by present day. The craton underwent ≥300 m of post-100 Ma elevation gain, based on~100 Ma marine sedimentary xenoliths entrained in~75-45 Ma kimberlites at modern elevations of 550-600 m. The transition from Paleozoic-Mesozoic subsidence to surface uplift may signal a change from predominantly northern (Franklinian-Innuitian) to western (Canadian Cordillera) plate boundary controls on continental interior processes, with the latter driving the east-to-west wave of unroofing. Canadian Cordillera evolution also affected the Cretaceous-early Tertiary history. Dynamic topography due to changing mantle flow regimes and proximity to sediment sources influenced the Phanerozoic surface evolution of the northwestern Canadian shield.

Zircon (U‐Th)/He thermochronology of Neoproterozoic strata from the Mackenzie Mountains, Canada: Implications for the Phanerozoic exhumation and deformation history of the northern Canadian Cordillera

“…[] in the Keele Tectonic Zone of the Mackenzie Plain partially overlaps with the Permo‐Triassic cooling history reported here for the Mackenzie Mountains and by Ault et al . [] for the western Slave craton.…”

“…The stratigraphic record of this depositional history was eroded by the early Mesozoic, recording the Middle Triassic cooling ages common in many samples in our data set. Our modeled Middle Triassic cooling event overlaps with circa 240 Ma exhumation modeled on the western margin of the Slave craton [ Ault et al ., , ]. We propose that this early Mesozoic cooling occurred diachronously throughout the region, potentially in response to far‐field stresses on the western margin of the continent.…”

Innovations in (U–Th)/He, Fission Track, and Trapped Charge Thermochronometry with Applications to Earthquakes, Weathering, Surface‐Mantle Connections, and the Growth and Decay of Mountains

“…In addition, the low‐temperature sensitivity and radiation damage influences on the apatite He system make it ideal for quantifying the timing, magnitude, and extent of low (<2 km) amplitude deposition and denudation episodes in cratonic regions, even when the deposited rocks have been completely eroded from the rock record. Apatite He date‐eU relationships inform long‐term thermal histories linked to these surface processes (e.g., Ault et al, , ; Ault, Flowers, & Bowring, ; Flowers, ; Flowers et al, ; Guenthner et al, ; Mackintosh et al, ). Figure presents apatite He, AFT, and zircon He data patterns from across the interior of continental North America.…”

Long-term cooling history of the Albertine Rift: new evidence from the western rift shoulder, D.R. Congo

“…The eU factor (effective Uranium concentration) was introduced (Shuster et al 2006) to account for the dependency of 4 He diffusion on the amount of accumulated crystal defects created by alpha-recoil in the crystal lattice. Radiation damage-influenced samples commonly show a positive age-eU correlation (single-grain age vs. eU concentration) and can provide valuable information on their thermal history (Flowers 2009;Ault et al 2013).…”