The Andes Active Subduction Orogeny
Convergent plate margins and subduction zones are first order features shaping the Earth. Convergent continental margins combine the majority of processes that affect the internal architecture thermal and geochemical character of continental lith- phere.
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Chapter 1 Deformation of the Central Andean Upper Plate System – Facts, Fiction, and Constraints for Plateau Models Chapter 2 The Time-Space Distribution of Cenozoic Volcanism in the South-Central Andes: a New Data Compilation and Some Tectonic Implications Chapter 3 Crustal Evolution at the Central Andean Continental Margin: a Geochemical Record of Crustal Growth, Recycling and Destruction Chapter 4 Long-Term Signals in the Present-day Deformation Field of the Central and Southern Andes and Constraints on the Viscosity of the Earth’s Upper Mantle Chapter 5 Tectonic Processes along the Chile Convergent Margin
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he introductory part comprises five chapters which deal with several of the largescale and first-order features that characterize the present architecture and the past evolution of the Central and Southern Andes. In the first chapter, O. Oncken et al. present a first complete quantitative assessment of the spatial and temporal pattern of deformation accumulation in the Central Andes. By means of time-series analysis they evaluate the alternative mechanisms that are considered to be most important for driving Andean deformation. They conclude that two factors: the rate of advance of the upper plate, and the rheologic properties of the plate interface, played the key roles in plateau building at the convergent plate margin. R. Trumbull et al. (Chap. 2) explore the time-space evolution of Cenozoic magmatism in the Central Andes, a key feature of the convergent plate margin, using a new compilation of volcanism and analysis by various statistical methods. They assess regional patterns of volcanic intensity with time, and compare these with the deformation record and with key structural-geometric features of the subduction system. The analysis reveals complex relationships of magmatism with processes operating at both regional and local scales, but there is clearly no direct relationship with upper-plate deformation. The compositional evolution of the Andean crust since the late Proterozoic is analyzed by G. Franz et al. in Chap. 3, with an emphasis on the issue of crustal growth vs. destruction at the convergent margin. Although convergent margins are commonly controlled by the addition of juvenile crust, the Andean case is shown not to be one of major continental growth, but of long term steady-state, where processes of growth, recycling, and destruction balance out. J. Klotz et al. (Chap. 4) provide a complete image of the ongoing deformation of the Central to South American Plate margin employing GPS measurements. Their results clearly indicate that elastic deformation associated with the seismic cycle governs the present-day situation in the fore-arc, whereas in the back-arc, the GPS record coincides with the signal of long-term geological deformation, documenting a progressive southward decrease of shortening velocity. C. Ranero et al. conclude this part from the marine perspective, showing the extreme diversity of the offshore fore-arc architecture from Northern to Southern Chile based mainly on high-res
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