Transition from diagenesis to metamorphism in a calcareous tectonic unit of the Iberian Variscan belt; Central Massif of the Picos de Europa, NW Spain

Transition from diagenesis to metamorphism has been characterized in the central part of the Picos de Europa unit (Cantabrian Zone) using conodont colour alteration index (CAI) complemented with Kubler index (KI) data. This unit essentially comprises Carboniferous limestone. The study leads us to de...

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Bibliographic Details
Published in:Geological magazine 2004-09, Vol.141 (5), p.617-628
Main Authors: Bastida, Fernando, Blanco-Ferrera, Silvia, García-López, Susana, Sanz-López, Javier, Valín, M. Luz
Format: Article
Language:English
Subjects:
absolute age
Alpine Orogeny
alteration
Cantabrian Mountains
carbonate rocks
Carboniferous
color alteration index
contact metamorphism
dates
deformation
diagenesis
Europe
extension
faults
fold and thrust belts
hydrothermal alteration
Iberian Peninsula
igneous and metamorphic rocks
K/Ar
low-grade metamorphism
metamorphism
metasomatism
mineralization
northwestern Spain
orogenic belts
orogeny
Paleozoic
petrography
Petrology
Picos de Europa
Pisuerga-Carrion Unit
sedimentary rocks
Southern Europe
Spain
stratigraphic boundary
Structural geology
tectonics
tectonostratigraphic units
thrust faults
Variscides
X-ray diffraction data
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Summary:Transition from diagenesis to metamorphism has been characterized in the central part of the Picos de Europa unit (Cantabrian Zone) using conodont colour alteration index (CAI) complemented with Kubler index (KI) data. This unit essentially comprises Carboniferous limestone. The study leads us to deduce two successive tectonothermal events. The first event generated a pattern with palaeotemperatures increasing towards the Pisuerga-Carrion unit, located S of the Picos de Europa unit. The present pattern is the result of an original dip to the N of the isothermal surfaces and the subsequent rising of the Picos de Europa unit along the frontal ramp of a deep Alpine thrust. This episode is interpreted as related to an extensional tectonic regime that occurred close to the Carboniferous-Permian boundary. The second event, which gave rise to thermal anomalies in the pattern of the first episode, was the result of hydrothermal processes in which fluid movement was facilitated by a dense network of fractures in the area close to the E section of the studied region. These processes gave rise to numerous mineralization events and have been related to a Permian extensional tectonic regime.
ISSN:0016-7568
1469-5081
DOI:10.1017/S0016756804009653