Publication: Evolución metamórfica hercínica de la región de Segovia (Sierra de Guadarrama)
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Publication Date
1991
Authors
Fúster Casas, José María
González Lodeiro, F.
Macaya, J.
Martín Parra, L.M.
Martínez Catalán, J.R.
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Sociedad Geológica de España
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Abstract
La región de Segovia representa uno de los sectores más profundos de la Sierra de Guadarrama, donde el metamorfismo regional hercínico alcanza la mayor intensidad. La evolución tectonometamórfica de este sector coincide con la que se encuentra en los niveles meso corticales de las cadenas con fuerte engrosamiento cortical. Una primera etapa prograda de media P/T (MI), contemporánea con la tectónica tangencial más intensa, da paso a un estadio paroxismal marcadamente descompresivo (M2) y a una etapa final retrógrada (M3).
Las condiciones metamórficas más extremas tuvieron lugar en la parte de alta temperatura de la facies de las anfibolitas. En las rocas pelíticas y cuarzo feldespáticas la desestabilización de la moscovita conduce a la aparición
de una extensa zona con ortosa + sillimanita, dentro de la cual queda incluida toda la región considerada. En las metabasitas, las condiciones termales más extremas vienen definidas por la coexistencia de hornblenda, diopsido y plagioclasa, que definen texturas subgranoblásticas con bordes de grano netos.
One of the deepest sectors of the Sierra de Guadarrama outcropsin the area around Segovia, where the Hercynian regional metamorphism reached high intensity. The tectonometamorphic evolution of the area is very similar to that considered as tipical of middle crustallevels in orogenic belts characterized by a strongly thickened crust. A first prograde stage of intermediate P/T (MI), coeval with nappe tectonics, was followed by a decbmpressive paroxysmal stage (M2) and, finally, by a last retrograde stage (M3). The metamorphic peak conditions reached the high temperature part of the amphibolite facies. Breaking down of moscovite in pelitic and quartzfeldspatic rocks led to the development of an orthoclase - sillimanite zone, inside of which all the studied area around Segovia is included. Subgranoblastic textures with sharp grain boundaries were developed in metabasic rocks during the thermal peak conditions. In these, coexistence of hornblende, diopsidic clinopyroxene and plagioclase indicate the same conditions for the metamorphic peak.
One of the deepest sectors of the Sierra de Guadarrama outcropsin the area around Segovia, where the Hercynian regional metamorphism reached high intensity. The tectonometamorphic evolution of the area is very similar to that considered as tipical of middle crustallevels in orogenic belts characterized by a strongly thickened crust. A first prograde stage of intermediate P/T (MI), coeval with nappe tectonics, was followed by a decbmpressive paroxysmal stage (M2) and, finally, by a last retrograde stage (M3). The metamorphic peak conditions reached the high temperature part of the amphibolite facies. Breaking down of moscovite in pelitic and quartzfeldspatic rocks led to the development of an orthoclase - sillimanite zone, inside of which all the studied area around Segovia is included. Subgranoblastic textures with sharp grain boundaries were developed in metabasic rocks during the thermal peak conditions. In these, coexistence of hornblende, diopsidic clinopyroxene and plagioclase indicate the same conditions for the metamorphic peak.