Unconformities as mineralogical breaks in the burial metamorphism of the Andes |
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| Authors: | Luis Aguirre Beatriz Levi Robin Offler |
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| Institution: | (1) Department of Geology, University of Liverpool, Liverpool, Great Britain;(2) Geologiska Institutionen, Stockholms Universitet, Stockholm, Sweden;(3) Geology Department, University of Newcastle, N.S.W., Australia |
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| Abstract: | Stratigraphical-structural units separated by regional unconformities in the Andes of Peru and Chile, display a pattern of low grade burial metamorphism. Each stratigraphical-structural unit shows a particular facies series covering part or all the range between the zeolite and the greenschist facies. These facies series were episodically generated as part of the geological evolution of each unit prior to its own folding. Mineralogical breaks are found to coincide with the regional unconformities and often cases of higher grade assemblages on top of lower grade ones occur. This pattern may be explained by a process of  sealing of each unit after its particular metamorphic episode took place. Porosity and permeability conditioning P
f, as demonstrated for individual lava flows, are the significant controlling factors in the production of the metamorphic assemblages. |
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