Elevator tectonics and orogenic collapse of a Tibetan-style plateau in the European Variscides: the role of the Bohemian shear zone |
| |
| Authors: | W Dörr G Zulauf |
| |
| Institution: | 1. Institut für Geowissenschaften, Universit?t Frankfurt a.M., Altenh?ferallee 1, 60438, Frankfurt am Main, Germany
|
| |
| Abstract: | Variscan collision of peri-Gondwanan terranes led to a doubly vergent crustal wedge that was thicker than 55 km in the area
of the Bohemian Massif. This crustal thickness resulted in a highly elevated Bohemian plateau with a topographic height >3–4 km.
The Bohemian plateau was covered with unmetamorphic Paleozoic strata, all of which are today well preserved in the Tepla–Barrandian
unit because of crustal-scale vertical slip along the Bohemian shear zone (BSZ). The BSZ forms a subvertical, ca. 500-km long
and up to 2-km wide belt of dip–slip mylonites which show several 90° deflections in map view. Tepla-Barrandian-down movements
were active under retrograde metamorphic conditions, starting with granulite and ceasing with greenschist facies conditions.
As slip along the BSZ was largely vertical and led to a minimum throw of 10 km, this type of crustal-scale deformation is referred to as elevator tectonics. The elevator-style movements caused the juxtaposition of the supracrustal Tepla–Barrandian lid (the “elevator”) against
high-grade rocks of the extruding orogenic root. The BSZ has further governed the foci of mantle-derived plutonism. New U–Pb
zircon and monazite TIMS dating of six plutons suggest that emplacement of mantle-derived melts along the BSZ lasted for at
least 20 m.y., starting with the emplacement of the Klatovy granodiorite at 347 +4/−3 Ma and ceasing with the emplacement
of the Drahotin pluton at 328 ± 1 Ma. When taking into account the new ages of synkinematic plutons, the simultaneous vertical
slip along the individual segments of the BSZ (North, West, and Central Bohemian shear zone) is bracketed to the period 343–337 Ma.
Elevator tectonics was probably controlled by delamination of thickened mantle lithosphere that caused a dramatic thermal
turnover and heating-up of the orogenic root. The overheated lower crust was thermally softened by anatexis and diffusion
creep resulting in channel flow, vertical extrusion, fast uplift, and exhumation of the orogenic root. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
