Field trip guide: Ridge-trench collision—The southern Patagonian Cordillera east of the Chile Triple Junction
Published:January 01, 2008
Matthew L. Gorring, 2008. "Field trip guide: Ridge-trench collision—The southern Patagonian Cordillera east of the Chile Triple Junction", Field Trip Guides to the Backbone of the Americas in the Southern and Central Andes: Ridge Collision, Shallow Subduction, and Plateau Uplift, Suzanne Mahlburg Kay, Víctor A. Ramos
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The southern Patagonian Cordillera south of the present location of the Chile Triple Junction (46.5°S) preserves distinctive deformational and backarc magmatic features that are a consequence of a series of northward-propagating ridge collision events that started at ca. 14 Ma. An abrupt increase of ~2000 m of topographic elevation and the exhumation and uplift of mid-Miocene to Pliocene plutons within the cordillera south of the Chile Triple Junction is accomplished by horizontal compressive deformation (both thin- and thick-skinned) within the Patagonian fold-thrust belt. Ridge-trench collisions have formed asthenospheric slab windows beneath the southern Patagonian Cordillera. Backarc magmatism associated with slab window formation includes a distinctive suite of adakites and extensive outpourings of oceanic island basalt (OIB)-like plateau basalts. The adakites formed from the partial melting of the young, hot trailing edge of the Nazca plate that preceded slab window opening, whereas the OIB-like plateau basalts formed from dynamic asthenospheric flow as the slab windows opened up beneath the backarc.
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Field Trip Guides to the Backbone of the Americas in the Southern and Central Andes: Ridge Collision, Shallow Subduction, and Plateau Uplift
The geologic field guides in this volume to the Andes of Argentina and Chile were written for the five field trips accompanying the 2006 Backbone of the Americas conference in Mendoza, Argentina, which was sponsored by the Geological Society of America and the Asociación Geológica Argentina. The meeting was organized around three processes influential in the evolution of the western margin and cordilleras of the Americas—ridge collision, shallowing and steepening subduction zones, and plateau and orogenic uplift. Designed for use in the office or the field, the field guides are to regions that highlight these themes and present up-to-date overviews with references. The trip in chapter 1 to southern Patagonia highlights the ridge-trench collision theme; the next three to different regions of the south-central Andes examine temporal and spatial issues related to shallowing subduction; and the trip in the last chapter to the central Andean Puna plateau highlights plateau uplift in the context of steepening subduction and lithospheric delamination.