| Title | Syncing fault rock clocks: Direct comparison of U-Pb carbonate and K-Ar illite fault dating methods |
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| Author | Mottram, C M; Kellett, D A ; Barresi, T; Zwingmann, H; Friend, M; Todd, A; Percival, J B |
| Source | Geology vol. 48, no. 12, 2020 p. 1179-1183, https://doi.org/10.1130/G47778.1  Open Access |
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| Year | 2020 |
| Alt Series | Natural Resources Canada, Contribution Series 20200143 |
| Publisher | Geological Society of America |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Subjects | geochronology; tectonics; Science and Technology; Nature and Environment; faults; fault zones; fault systems; uranium lead dating; potassium argon dating |
| Illustrations | tables; plots; photographs; figures; location maps |
| Program | GEM2: Geo-mapping for Energy and Minerals Western Cordillera |
| Released | 2020 08 19 |
| Abstract | The timing of slip on brittle faults in Earth's upper crust is difficult to constrain, and direct radiometric dating of fault-generated materials is the most explicit approach. Here we make a direct
comparison between K-Ar dating of fault gouge clay (authigenic illite) and U-Pb dating of carbonate slickenfibers and veins from the same fault. We have dated fault generated materials from the Big Creek fault, a northwest-striking, dextral
strike-slip fault system in Yukon Territory, Canadian Cordillera. Both methods yielded dates at ca. 73 Ma and ca. 60-57 Ma, representing at least two periods of fault slip that form part of a complex fault and fluid-flow history. The Cretaceous
result lies within previous indirect estimates for major slip on the fault. The Paleocene-Eocene result coincides with the estimated timing of slip of the nearby Tintina and Denali faults, which are crustal-scale, northwest-striking dextral faults,
indicating Big Creek fault reactivation during regional faulting. The coincidence of periods of carbonate-crystallizing fracturing and fluid flow with intervals of seismic, gouge-generating slip supports the fault valve model, where fault strength is
mediated by fluid pressures, and fluid emplacement requires seismic pumping in otherwise impermeable aseismic fault zones. The reproducibility of slip periods for distinct fault-generated materials using different decay systems indicates that these
methods provide complimentary results and can be reliably applied to date brittle fault slip, opening new opportunities for investigating fault conditions with associated mineralizing fluid events. |
| Summary | (Plain Language Summary, not published)
Faults, or breaks in the Earth's crust across which rocks are displaced, are difficult to precisely situate in geological history. However, there are a
few established and emerging methods for dating rock materials generated in faults. In this study we make the first comparison between two of those methods: dating fault-related calcite using the U-Pb method and dating fault gouge illite using the
K-Ar method. Our results show that both methods reproduce the same fault slip history, with slip occurring at ca. 73 Ma and ca. 58 Ma. |
| GEOSCAN ID | 327889 |
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