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Evidence from Rb–Sr mineral ages for multiple orogenic events in the Caledonides of Shetland, Scotland by S. Walker, M. F. Thirlwall, R. A. Strachan, and.

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Presentation on theme: "Evidence from Rb–Sr mineral ages for multiple orogenic events in the Caledonides of Shetland, Scotland by S. Walker, M. F. Thirlwall, R. A. Strachan, and."— Presentation transcript:

1 Evidence from Rb–Sr mineral ages for multiple orogenic events in the Caledonides of Shetland, Scotland by S. Walker, M. F. Thirlwall, R. A. Strachan, and A. F. Bird Journal of the Geological Society Volume 173(3): May 3, 2016 © 2016 The Author(s)‏

2 (a) Simplified geological map of Shetland including sample sites on Mainland.
(a) Simplified geological map of Shetland including sample sites on Mainland. (b) Regional context of Shetland in its pre-Mesozoic rifting setting (modified from Bird et al. 2013). Ages shown in grey are biotite–feldspar ages; all others are white mica–feldspar. WBF, Walls Boundary Fault; WKSZ, Wester Keolka Shear Zone; IS, Iapetus Suture; SUF, Southern Uplands Fault; HBF, Highland Boundary Fault; GGF, Great Glen Fault; MTZ, Moine Thrust Zone; NHT, Northern Highland Terrane; MTrFZ, Møre–Trøndelag Fault Zone; ESB, East Shetland Basin; UH, Utsira High; CB, Clew Bay. Asterisk indicates ages that are not robust. S. Walker et al. Journal of the Geological Society 2016;173: © 2016 The Author(s)‏

3 Geology of the North Roe region of northern Mainland Shetland, including sample sites and age determinations. Geology of the North Roe region of northern Mainland Shetland, including sample sites and age determinations. S. Walker et al. Journal of the Geological Society 2016;173: © 2016 The Author(s)‏

4 Geology of the islands of Yell, Unst and Fetlar in Shetland, including sample sites and age determinations. Geology of the islands of Yell, Unst and Fetlar in Shetland, including sample sites and age determinations. Ages shown in grey are biotite–feldspar ages; all others are of white mica. Asterisk indicates ages that are not robust. S. Walker et al. Journal of the Geological Society 2016;173: © 2016 The Author(s)‏

5 Graphical representation of Caledonian ages in Shetland, including data from this study and other modern geochronological work. Graphical representation of Caledonian ages in Shetland, including data from this study and other modern geochronological work. For ages where no error bars are shown, uncertainties are smaller than the marker symbol. S. Walker et al. Journal of the Geological Society 2016;173: © 2016 The Author(s)‏

6 Rb–Sr isochron diagrams for samples where multiple mica separates were analysed.
Rb–Sr isochron diagrams for samples where multiple mica separates were analysed. Pl, plagioclase fraction; Ms, white mica, with fraction indicated numerically. Error bars are smaller than symbols. S. Walker et al. Journal of the Geological Society 2016;173: © 2016 The Author(s)‏

7 Representative thin section photomicrographs in plane-polarized light: (a) SW12-07; (b) SW13-17; (c) SW12-14; (d) SW13-25. Representative thin section photomicrographs in plane-polarized light: (a) SW12-07; (b) SW13-17; (c) SW12-14; (d) SW Mineral name abbreviations taken from Kretz (1983). S. Walker et al. Journal of the Geological Society 2016;173: © 2016 The Author(s)‏

8 Thin section photomicrographs in plane-polarized light from North Roe: (a) SW12-01; (b) SW12-02; (c) SW13-01; (d) SW13-03. Thin section photomicrographs in plane-polarized light from North Roe: (a) SW12-01; (b) SW12-02; (c) SW13-01; (d) SW Mineral name abbreviations taken from Kretz (1983). S. Walker et al. Journal of the Geological Society 2016;173: © 2016 The Author(s)‏


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