Tectonothermal evolution in the core of an arcuate fold and thrust belt: the south-eastern sector of the Cantabrian Zone (Variscan belt, north-western Spain)
The tectonothermal evolution of an area located in the core of the Ibero-Armorican Arc (Variscan belt) has been determined by using the conodont colour alteration index (CAI), Kübler index of illite (KI), the Árkai index of chlorite (AI) and the analysis of clay minerals and rock cleavage. The area...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-07-01
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| Series: | Solid Earth |
| Online Access: | http://www.solid-earth.net/7/1003/2016/se-7-1003-2016.pdf |
| Summary: | The tectonothermal evolution of an area located in the core of the
Ibero-Armorican Arc (Variscan belt) has been determined by using the conodont
colour alteration index (CAI), Kübler index of illite (KI), the Árkai
index of chlorite (AI) and the analysis of clay minerals and rock cleavage.
The area is part of the Cantabrian Zone (CZ), which represents the foreland
fold and thrust belt of the orogen. It has been thrust by several large units
of the CZ, what resulted in the generation of a large number of synorogenic
Carboniferous sediments. CAI, KI and AI values show an irregular distribution
of metamorphic grade, independent of stratigraphic position. Two
tectonothermal events have been distinguished in the area. The first one,
poorly defined, is mainly located in the northern part. It gave rise to very-low-grade metamorphism in some areas and it was associated with a deformation
event that resulted in the emplacement of the last large thrust unit and
development of upright folds and associated cleavage (<i>S</i><sub>1</sub>). The second
tectonothermal event gave rise to low-grade metamorphism and cleavage
(<i>S</i><sub>2</sub>) crosscutting earlier upright folds in the central, western and
southern parts of the study area. The event continued with the intrusion of
small igneous rock bodies, which gave rise to contact metamorphism and
hydrothermal alteration. This event was linked to an extensional episode due
to a gravitational instability at the end of the Variscan deformation. This
tectonothermal evolution occurred during the Gzhelian–Sakmarian.
Subsequently, several hydrothermal episodes took place and local crenulation
cleavage developed during the Alpine deformation. |
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| ISSN: | 1869-9510 1869-9529 |