Tectonic Development of the North Chilean Andes in Relation to Plate Convergence and Magmatism Since the Jurassic

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Abstract

Since the early Jurassic the magmatic arc of the north Chilean Andes has been displaced from the Coastal Cordillera to the Western Cordillera. This eastward migration happened stepwise and four successive, ± stationary arc systems can be distinguished. The deformation history of the arc systems in relation to plate convergence and igneous activity shows that the magmatic arc, a zone of relative crustal weakness, reacted very sensitively to changing conditions of plate convergence. Both long-term continuous deformations and short-term tectonic events are recognized. They reflect periods of more or less steady state conditions and relatively sudden changes of subduction parameters respectively. Two major periods of different deformational styles, related to differing plate configurations and accompanying convergence obliqueness, can be distinguished: (1) 200–90 Ma (sinistral convergence obliqueness >45°) with general (trans-)tension during tectonic phases and interphases, and (2) since 90 Ma (dextral convergence obliqueness <45°) with transpression during phases and slight extension in interphases.