Temporal and spatial evolution of orogens: a guide for geological mapping

Description

Orogens develop in convergent settings involving twoor more continental and/or oceanic plates. They are tra-ditionally defined as zones of crustal deformation associ-ated with mountain building resulting from either accretionof a terrane and/or an arc, continent-continent collision or rift-inversion. However, this definition does not considerthe genetic link between an oceanic domain and an intra-continental rift, even though extension associated with ascissor-shape opening can be demonstrated in many ocean-floored basins. Consequently, we propose a new conceptof orogenic evolution based on the development of exten-sional margins subsequently subjected to crustal shorten-ing. Thus orogens that develop as a result of the closureof wide basins, are distinguished from mountain belts devel-oped above subduction zones or that result from conti-nental collision and inverted intra-continental rifts. Ourreview of several key orogens identifies similarities anddifferences in geodynamic processes through geologicaltime including prior to the onset of plate tectonics ca. 2.5Ga. We propose that mapping based on comparative tec-tonics is a good way to constrain such an evolution, andthat this can start with a global-scale map of past-to-modernorogens aimed at re-exploring mountain building conceptsspatially and temporarily. This is the primary objective ofIGCP 667 project "World Map of Orogens".

Abstract

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