A continuous thermal history for southern Baffin Island, Canada over the
past 1.8 billion years: Implications for the assembly of Rodinia and the
rifting of Greenland
Abstract
New and recently published U-Pb, muscovite-biotite 40Ar/39Ar, K-feldspar
MDD 40Ar/39Ar, zircon and apatite (U-Th)/He, and apatite fission-track
data were compiled and inverted for a comprehensive, thermal history of
southern Baffin Island, Canada. This work is a contribution to the
Geo-mapping for Energy and Minerals (GEM) Baffin Island initiative and
Trans-GEM synthesis of the Phanerozoic exhumation history of the
Canadian Shield. Southern Baffin Island is comprised of Archean plutonic
basement metamorphosed during the Trans-Hudson Orogeny. Monazite U-Pb
dating on the Hall Peninsula suggest peak metamorphic conditions were at
ca. 1850-1820 Ma and remained at >550ºC ca. 100 My after
the thermal peak [1], while 40Ar/39Ar hydrous mineral ages and
modeling suggest temperatures remained at >420-450ºC ca.
150-200 My after peak conditions [2]. New apatite U-Pb age
populations are in agreement and range from 1674 ± 35 Ma to 1796 ± 75 Ma
(2σ), suggesting elevated post-THO temperatures at
~450ºC. During the Meso- to Neoproterozoic the Hall
Peninsula region experienced prolonged slow cooling on the order of
≤0.5ºC/My until ca. 1000 Ma when cooling accelerated to
~1ºC/My due to supercontinent Rodinia assembly.
Sedimentary sequences place minimum timing constraints on basement rocks
being at near-surface conditions in the early Paleozoic. Preliminary
results from apatite fission-track data suggest that southwest Baffin
(Meta-Incognita and Hall Peninsula) was fully exhumed by Paleozoic time
during basement uplift that likely exploited preexisting, regional
structures. Nearby Foxe Basin sediments suggest this region of the
Canadian Shield was exhumed by the Late Ordovician (ca. 450 Ma) and
either remained topographically high, or experienced minor burial during
subsequent continental-wide transgression and shallow marine carbonate
deposition in the Silurian-Devonian. AFT data from a >1890
Ma volcanic tuff cutting the Paleoproterozoic Hoare Bay Group sediments
on the easternmost Cumberland Peninsula record rapid cooling in the
Jurassic. The cooling signal recorded along Cumberland Peninsula is
likely due to early crustal thinning related to rifting of Greenland
from mainland Canada during Pangaea breakup and aligns with a model of
rift-flank uplift. AFT models are in agreement with ages of dike swarms
in West Greenland given as evidence by [3] for the onset of rift
extension. The summarized cooling history of southern Baffin Island
suggests post-THO cooling rates of ~1-3ºC/My from ca.
1700-1500 Ma, followed by slow cooling and Mesoproterozoic cooling
pulses at ca. 1300 Ma and ca. 1000-950 Ma, likely due to Rodinia
assembly. Rocks have been at temperatures <100ºC since ca. 500
Ma. [1] Skipton et al., 2016, J. of Petrology, v.57(8); [2]
Skipton et al., 2017, Lithos, v.284; [3] Larsen et al., 2009, J.
Geol. Soc., v.166.