Volume 38: January - December 1997
Issue 1: January 1997
and A .Azor M .Ballevre 2 , 1Departamento de Geodinamica, Universidad de Granada, Facultad de Ciencias, Campus Fuentenueva S/N, E-18002 Granada ,Spain and 2Laboratoire de Petrologie-Geochimie, Geosciences Rennes (UPR-CNRS 4661), Universite Rennes I, F-35042 Rennes cedex,France Corresponding author
ABSTRACT A low-pressure metamorphic zonation ranging from biotite to migmatite zones occurs in the Sierra Albarrana area (Varican Belt of southwestern Iberian Peninsula) in uppermost Precambrian to Lower Palaeozoic metasedimentary rocks. The principal deformation in this area is related to a major ductile shear zone whose central part is localized immediately to the southwest of the Sierra Albarrana Quartzites. The metamorphism is synchronous with respect to this deformation. The metamorphic zones are symmetrically distributed with respect to the Sierra Albarrana Quartzites. Pressure-temperature (P-T) conditions are 3.5-4 bar and range for 400oC (biotite zone) to 500oC (staurolite-garnet zone) up to 650-700oC (migmatite zone). We have not detected pressure variations along the different metamorphic zones. Relic kyanite is observed in the form of inclusions in andalusite within veins in the lower-grade part of the staurolite-andalusite zone. The low-pressure metamorphism of the Sierra Albarrana area arises for a two-stage history including moderate crustal thickening followed by subsequent localization of deformation in a transcurrent shear zone during peak P-T conditions. Channelized fluid flow within the major ductile shear zone may have contributed to the heat budget of the low-pressure metamorphism.
: fluid flows; Iberian Massif; low-pressure metamorphism; shear zone; Sierra Albarrana area Keywords
Pages:
35 -64
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