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

作者：Powell Jeremy W^*; Schneider David A; Issler Dale R

来源：Basin Research, 2018, 30: 497-512.

DOI：10.1111/bre.12233

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 +/- 36.9Ma to 47.1 +/- 12.3Ma, and 16.8 to 10.2m, and single crystal AHe dates are between 57.9 +/- 3.5 and 42.0 +/- 2.5Ma with effective uranium concentrations from 17ppm to 36ppm. The fission track data show no relationship with the kinetic parameter D-par and fail the (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 similar to 65-90 degrees 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.

• 出版日期2018-2