EUROPROBE News 9
URALIDES: A Key to Understanding Collisional Orogeny
by Andrés Pérez-Estaún, Dennis Brown (Barcelona) and
Uralides colleagues
The
Uralide orogen is one of Earth's great structural discontinuities. It is the geographic
and geological divide between Europe and Asia. Together with the Appalachian, Caledonian
and Variscan orogens, it was one of the major zones of continental convergence that
contributed to the assembly of the late Palaeozoic supercontinent Pangaea. Wedged between
the East-European Craton to the west and the Angara Craton to the east, the Uralides
include a 2500-km-long suture zone that juxtaposes a collage of accreted oceanic, island
arc and microcontinental terranes against a west-vergent thrust stack of foreland basin
and continental margin rocks.
Although
the Uralide orogen has many features in common with other Palaeozoic orogens, it has a
number of important distinguishing characteristics; not least, it remains more or less
intact, uninfluenced by Mesozoic or Tertiary sea-floor spreading. Some of these unique
characteristics offer opportunities for significant advances in our general understanding
of orogenesis.
A
major objective of EUROPROBE's URALIDES Project is a multidisciplinary investigation into
the structure and evolution of the Uralide orogen. In addition to resolving key problems
related to the general architecture and formation of the orogen itself and to the assembly
of Pangaea, several other world-class issues will be addressed, as follows:
Studies
of anomalously thick crust along the axis of the orogen may yield clues as to how mountain
roots are generated and preserved.
Exceptionally
well-preserved ophiolites and volcanic-arc assemblages, which extend throughout the length
of the mountain belt, allow processes associated with Palaeozoic ocean crust formation and
subduction to be explored.
Mechanisms
that control the exhumation of crustal material from great depth (50-80 km) will be
examined through investigations of spectacular outcrops of high pressure metamorphic
rocks.
The
well-documented peneplanation of the mountain belt by the Jurassic and the relatively
recent anomalous uplift history lend the Uralides to studies of post-orogenic exhumation
and uplift mechanisms.
Comparison
of seismic reflection data with very deep borehole information (current depth of the
Uralian superdeep drillhole is 5.3 km; target depth is 15 km) should provide new
constraints on the origin of seismic reflections from crystalline crust.
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