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TitleBurial and exhumation history of the Mackenzie Plain, NWT, Canada: integration of apatite (U-Th)/He and fission track thermochronometry
AuthorPowell, JORCID logo; Schneider, D; Issler, DORCID logo; Stockli, D
SourceThermo 2016: 15th International Conference on Thermochronology, abstracts; 2016 p. 141-142 Open Access logo Open Access
LinksOnline - En ligne (complete volume - volume complet, PDF, 36.9 MB)
Alt SeriesNatural Resources Canada, Contribution Series 20190422
MeetingThermo 2016: 15th International Conference on Thermochronology; Maresias; BR; September 18-23, 2016
Mediaon-line; digital
File formatpdf
ProvinceNorthwest Territories
AreaMackenzie Plain
Subjectsgeochronology; sedimentology; Science and Technology; Nature and Environment
ProgramGEM2: Geo-mapping for Energy and Minerals Mackenzie Corridor, Shield to Selwyn
Released2016 09 01
AbstractSedimentary strata from the Mackenzie Plain, currently in the foreland of the Mackenzie Mountains of the northern Canadian Cordillera, record a dynamic geologic history from the Paleozoic through to the Paleogene. Whereas Late Cretaceous to Paleogene foreland basin strata presently cover the Plain, uncomformities throughout the sedimentary succession indicate that episodic burial and exhumation are a common theme through deep time. Knowledge of the timing and magnitude of these events is especially critical for understanding potential hydrocarbon systems, as the timing of maturation for the Devonian source rock is a major uncertainty for oil and gas exploration. Howeer, quantitative thermochronology studies for the region are sparse, and limited to Neoproterozoic strata from the mackenzie Mountains and a single well in the Mackenzie Plain. To better understand the tectonic and thermal evolution of the study area, samples were collected for apatite (U-Th)/He (AHe) and fission track (AFT) thermochronometry. Strategic sampling followed a transect along the deformation front and across the Plain. We targeted outcrops of the Devonian Imperial Formation and the Late Cretaceous Slater River Formation. These formations straddle a significant regional unconformity, and ultimately help to quantify the magnitude of the late Paleozoic to early Mesozoic thermal history in comparison with the Late Cretaceous to Paleocene thermal event related to foreland basin development. We report 61 single-grain AHe dates from seven samples. AHe dates vary from 225 ± 14 Ma to 3 ± 0.2 Ma, with the majority of dates recording cooling between the Late Cretaceous to Miocene. Whereas several samples exhibit correlations between AHe date and parameters such as radiation damage (eU) and grain size, all samples demonstrate varying degrees of intra-sample date dispersion. All five samples chosen for AFT thermochronology display an even greater degree of variation, with AFT dates scattered between the Cambrian and Miocene throughout out dataset. Although no correlations exist between DPAR and AFT age or track length distribution, we note a strong relationship between grain chemistry and ages. We use the parameter rmr03 to distinguish up to four discrete kinetic populations per sample, with consistent Triassic, Cretaceous and Miocene pooled ages. Inverse thermal history modeling of AFT and AHe samples reveals that the Devonian strata likely reached maximum burial temperatures (130ºC-180ºC) prior to Triassic unroofing. Strata were reheated to lower temperatures in the Cretaceous to Paleogene (90ºC-120ºC), and have a dog-legged Cenozoic cooling history, with an initial Paleocene phase related to Cordilleran deformation and a final Miocene phase. This t-T information is used to assess 1D burial histories of local wells and the hydrocarbon potential of regional Devonian and Cretaceous source rocks. Ultimately, these data reflect the complications, and possibilities, of low-temperature thermochronology in sedimentary rocks where detrital variance results in a broad chemistry range in the apatite population. We used chemistry-dependent fission track annealing kinetics to explain dispersion in both our AFT and AHe datasets and detail the thermal history of strata that have experienced a protracted cooling history through the uppermost crust.

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