Temporal and spatial evolution of orogens: a guide for geological mapping
Résumé
Orogens develop in convergent settings involving two
or more continental and/or oceanic plates. They are traditionally defined as zones of crustal deformation associated with mountain building resulting from either accretion
of a terrane and/or an arc, continent-continent collision
or rift-inversion. However, this definition does not consider
the genetic link between an oceanic domain and an intracontinental rift, even though extension associated with a
scissor-shape opening can be demonstrated in many oceanfloored basins. Consequently, we propose a new concept
of orogenic evolution based on the development of extensional margins subsequently subjected to crustal shortening. Thus orogens that develop as a result of the closure
of wide basins, are distinguished from mountain belts developed above subduction zones or that result from continental collision and inverted intra-continental rifts. Our
review of several key orogens identifies similarities and
differences in geodynamic processes through geological
time including prior to the onset of plate tectonics ca. 2.5
Ga. We propose that mapping based on comparative tectonics is a good way to constrain such an evolution, and
that this can start with a global-scale map of past-to-modern
orogens aimed at re-exploring mountain building concepts
spatially and temporarily. This is the primary objective of
IGCP 667 project “World Map of Orogens”
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