Application of multi‐kinetic apatite fission track and (U‐Th)/He thermochronology to source rock thermal history: a case study from the Mackenzie Plain, NWT, Canada

Abstract

Shale of the Upper Cretaceous Slater River Formation extends across the Mackenzie Plain of the Canadian Northwest Territories and has potential as a regional source rock because of the high organic content and presence of both oil-and gas-prone kerogen. An understanding of the thermal history experienced by the shale is required to predict any potential petroleum systems. Our study integrates multi-kinetic apatite fission track (AFT) and apatite (U-Th)/He (AHe) thermochronometers from a basal bentonite unit to understand the timing and magnitude of Late Cretaceous burial experienced by the Slater River Formation along the Imperial River. We use LA-ICP-MS and EPMA methods to assess the chemistry of apatite, and use these values to derive the AFT kinetic parameter r mr0 . Our AFT dates and track lengths, respectively, range from 201.5 AE 36.9 Ma to 47.1 AE 12.3 Ma, and 16.8 to 10.2 lm, and single crystal AHe dates are between 57.9 AE 3.5 and 42.0 AE 2.5 Ma with effective uranium concentrations from 17 ppm to 36 ppm. The fission track data show no relationship with the kinetic parameter D par and fail the v 2 -test indicating that the data do not comprise a single statistically significant population. However, when plotted against their r mr0 value, the data are separated into two statistically significant kinetic populations with distinct track length distributions. Inverse thermal history modelling of both the multi-kinetic AFT and AHe datasets, reveal that the Slater River Formation reached maximum burial temperatures of 65-90°C between the Turonian and Paleocene, indicating that the source rock matured to the early stages of hydrocarbon generation, at best. Ultimately, our data highlight the importance of kinetic parameter choice for AFT and AHe thermochronology, as slight variations in apatite chemistry may have significant implications on fission track and radiation damage annealing in apatite with protracted thermal histories through the uppermost crust.

Deformation at the eastern margin of the Northern Canadian Cordillera: Potentially related to opening of the North Atlantic

“…These samples (MAC‐12,‐39,‐41) experienced very slow cooling or steady state conditions within 120–80°C throughout the Late Cretaceous followed by Paleocene–Early Eocene rapid cooling to below 50°C (Figure ). These two phases of rock exhumation in the Mackenzie Mountains correlate well with the burial histories of the Devonian (MAC‐44) and Upper Cretaceous (MAC‐45) strata collected in the Mackenzie Plain (Figure b), and the apatite fission track multi‐kinetic thermal models of Devonian (Issler et al., ) and Cretaceous strata (Powell, Schneider, & Issler, ) farther south. Our thermal history models of strata in the Mackenzie Plain suggest burial and heating up to ~140°C during Paleocene–Eocene time, which is coeval with cooling phase two documented in the Mackenzie Mountains (Figure ).…”

Reconstructing deep‐time histories from integrated thermochronology: An example from southern Baffin Island, Canada

“…() and Ketcham et al. (), respectively, to model AFT ages and c‐axis projected track length distributions (see Powell, Schneider, and Issler () and Schneider and Issler () for recent examples of this approach). The kinetic populations for the samples on Cumberland Peninsula are much younger and suggest greater resetting later in their respective histories when compared to the southwestern Baffin samples.…”

Exhuming the Canadian Shield: preliminary interpretations from low-temperature thermochronology and significance for the sedimentary succession of the Hudson Bay Basin

“…The implications for modelling are that multikinetic AFT behaviour narrows the possibilities of thermal-history solutions that satisfy the FT data for all grain-age populations from a single sample during simultaneous thermal-history modelling [43,47,16,45]. A single sample may contain between two to four resolvable kinetic populations ranging in thermal sensitivity from under 70 • C to over 200 • C [44], extending the temperature range of the modelled thermal histories beyond the canonical "100-110 • C" quoted in most AFT studies, which employ a mono-compositional scheme and assume a typical fluorapatite composition.…”

“…The CRS approach is described thoroughly in Willett [69], Harrison et al [71], McDannell [15], McDannell et al [8,16], and McDannell and Flowers [18]. The most current AFTINV modelling approaches are discussed in Powell et al [47,72], McDannell et al [16], and Schneider and Issler [45].…”