Download Auxiliary Material for Plate rotation during continental collision and

Auxiliary Material for
Plate rotation during continental collision and its relationship with the exhumation of UHP
metamorphic terranes: application to the Norwegian Caledonides.
A. D. Bottrill1, J. van Hunen1, S. J. Cuthbert2, H.K. Brueckner3, and M. B. Allen1
[1]Department of Earth Sciences, Durham University, Durham, DH1 3LE, UK 5
[2] School of Science, University of the West of Scotland, Paisley PA1 2BE, UK 6
[3] Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA
Introduction
These figures show the mesh (fs01.eps) and the results of a resolution test (fs02.eps) for the
numerical model used in this study. A map of the major tectonic units and structural feature is
included (fs03.eps). Plots that show the subduction history of all markers for both the orthogonal
(fs04.eps) and diachronous (fs08.eps) collision models and P-T paths for all markers used in the
study(fs05.eps, fs06.eps, fs07.eps, fs09.eps, fs10.eps, fs11.eps). A plate reconstruction of the
Laurentia Baltica collision is also provided (fs12.eps) with an animated version (ms02.gif). A 3D
animation showing the dynamics of a diachronous collision (ms01.gif).
1. fs01.eps (Figure i) A section through the numerical grid used in the model calculation the
grid in the region of the collision zone is 10 km by 20 km by 10 km in the x,y,z directions
respectively. The red contour shows the outline of the two plates. The model had ~9×105
nodes.
2. fs02.eps Figure ii Comparison of the P-T paths travelled for the same tracer from the
standard resolution model used in this study and a double resolution model. The standard
model take 36 hours to run on 64cores the double resolution take 7 days on 128 cores.
3. fs03.eps Figure iii Adapted from [Brueckner and Cuthbert, 2013] showing the main structural
and tectonic features of the WGC. The Grey scale of the Calidonized basement represents
the degree of metamorphism experienced with darker being higher temperatures and
pressures. The two nape complexes where formed in the acretionary prism of the Laurentia
Baltic collision and have ridden on top of the basement as it educted.
4. fs04.eps Figure iv Vertical cross sections perpendicular to the subduction trench through the
orthogonal collision model. Colour scheme shows viscosity, white contour highlights crustal
material and stars show the position of followed material markers. The first, second, and
third column shows a slice at y=660, 1320, and 1980 km and contains the red, yellow and
blue family of markers, respectively. Markers follow similar paths at the 3 different locations
along the subduction zone.
5. fs05.eps Figure v P-T paths for markers at y=660 km from the orthogonal collision model.
The P-T paths are organised in the x-z orientation that the markers where originally
positioned in, in the front of the subducting plate’s continental block e.g. the PT paths on
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the top left of the figure is for a tracer that started at the surface and at the front of the
front of the subducting plate’s continental block. Markers are placed between 0-30 km
depth (z-axis) and 0-240 km from the edge of the continental block. See Figure 2 for more
details on the start positions of the markers.
fs06.eps Figure vi P-T paths for markers at y=1320 km from the orthogonal collision model.
The P-T paths are organised in the x-z orientation that the markers where originally
positioned in, in the front of the subducting plate’s continental block e.g. the PT paths on
the top left of the figure is for a tracer that started at the surface and at the front of the
front of the subducting plate’s continental block. Markers are placed between 0-30 km
depth (z-axis) and 0-240km from the edge of the continental block. See Figure 2 for more
details on the start positions of the markers.
fs07.eps Figure vii P-T paths for markers at y=1980 km from the orthogonal collision model.
The P-T paths are organised in the x-z orientation that the markers where originally
positioned in, in the front of the subducting plate’s continental block e.g. the PT paths on
the top left of the figure is for a tracer that started at the surface and at the front of the
front of the subducting plate’s continental block. Markers are placed between 0-30 km
depth (z-axis) and 0-240km from the edge of the continental block. See Figure 2 for more
details on the start positions of the markers.
fs08.eps Figure viii Vertical cross sections perpendicular to the subduction trench through
the diachronous collision model. Colour scheme shows viscosity, white contour highlights
crustal material and stars show the position of followed material markers. The first, second,
and third column shows a slice at y=660, 1320, and 1980 km and contains the red, yellow
and blue family of markers, respectively. Markers follow similar paths at the 3 different
locations along the subduction zone.
fs09.eps Figure ix P-T paths for markers at y = 660 km from the diachronous collision model.
The P-T paths are organised in the x-z orientation that the markers where originally
positioned in, in the front of the subducting plate’s continental block e.g. the PT paths on
the top left of the figure is for a tracer that started at the surface and at the front of the
front of the subducting plate’s continental block. Markers are placed between 0-30 km
depth (z-axis) and 0-240km from the edge of the continental block. See Figure 2 for more
details on the start positions of the markers.
fs10.eps Figure x P-T paths for markers at y = 1320 km from the diachronous collision model.
The P-T paths are organised in the x-z orientation that the markers where originally
positioned in, in the front of the subducting plate’s continental block e.g. the PT paths on
the top left of the figure is for a tracer that started at the surface and at the front of the
front of the subducting plate’s continental block. Markers are placed between 0-30 km
depth (z-axis) and 0-240km from the edge of the continental block. See Figure 2 for more
details on the start positions of the markers.
fs11.eps Figure xi P-T paths for markers at y = 19800 km from the diachronous collision
model. The P-T paths are organised in the x-z orientation that the markers where originally
positioned in, in the front of the subducting plate’s continental block e.g. the PT paths on
the top left of the figure is for a tracer that started at the surface and at the front of the
front of the subducting plate’s continental block. Markers are placed between 0-30 km
depth (z-axis) and 0-240km from the edge of the continental block. See Figure 2 for more
details on the start positions of the marker.
12. fs12.eps Figure xii Plate reconstruction showing the motion of Baltica relative to a stable
Laurentia between 470-430 Ma. The red path shows the associated rotational poles of
Baltica between 445-430 Ma. The reconstruction shows how Baltica rotates anticlockwise during its collision with Laurentia. Baltica’s rotational pole propagates north
roughly parallel to the position of the eventual suture between Laurentia and Baltica.
This reconstruction show that Baltica that the rotation rate of Baltica increases around
435 Ma as the rotational pole continued to move north until 430 Ma. The paleomagnetic
reconstructions are therefore broadly consistent (within the uncertainties in the locations
of paleomagnetic poles) with the diachronous collisional model during initial continental
subduction. Figure produced from data in [Torsvik et al., 2012].
13. ms01.gif Animation showing the dynamics of a diachronous collision and the subsequent
tearing off of the subducted slab. The blue shows and iso-temperature surface and green
shows the position of continental crust.
14. ms02.gif Plate reconstuction based on (Torsvik 2012) showing the collision of Laurentia and
Baltic in a stable Laurentia reference frame. The rotational pole of Baltic moves north
parallel to the collision zone for 15 Myr before collision.