The arc of the western Alps in the light of geophysical data on deep crustal structure

Article Abstract:

It has been possible to distinguish three episodes of post-collisional crustal shortening along the Etude Continentale et Oceanique par Reflexion et Refraction Sismique - Progetto Strategico Crosta Profonda (ECORS-CROP) transect in the western and central Alps. Direct comparison of the three transects indicates that the style of deformation and, especially, dating of individual tectonic and metamorphic events differ considerably. It is suggested that the creation of the western Alpine arc was initiated by head-on early Tertiary collision of the convex European plate boundary zone with the Adriatic microplate in what later became the central and eastern Alps.

Alps

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Tectonic entrapment and its role in the evolution of continental lithosphere: An example from the Precambrian of western Canada

Article Abstract:

New Lithoprobe geophysical data collected in 1992 in central Alberta, Canada, supply new constraints on the nature of the boundary zone and the internal structure of the Hearne province, an Archean continental fragment. These data are particularly significant in offering constraints on the internal deformation of the crust and mantle of the Hearne province and give new insights into the bounding orogens to the Hearne province. The current reflection geometries are a result of a Proterozoic tectonic vise that formed during coeval underthrusting of the Archean Hearne province along subduction zones with opposing dips.

Alberta

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Role of melt in the formation of a deep-crustal compressive shear zone: the Maclaren Galcier metamorphic belt, south central Alaska

Article Abstract:

Studies of the Maclaren metamorphic belt in south central Alaska shed light on deep-crustal shear zone formation. The belt is composed of a cool, low-grade rock layer overlain by hot, upper amphibolite facies. Analysis indicates that melt intrusion occured repeatedly during shear zone compression. A thermal model for sill-like plutons predicts the presence of melt in deep crust for extended periods. The belt's tonalite is estimated to have crystallized within a minimum of 90,000 years. Ten kilometers of displacement across the sill in the presence of melt is also suggested.

Alaska, Glaciology, Glaciers, Sills (Geology)

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