Publication: El metamorfismo en la Cuenca de los Cameros.
Geocronología e implicaciones tectónicas
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Publication Date
1992
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Sociedad Geológica de España
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Abstract
A case of hydrothermal metamorphism is described from the Cameros Basin along the rio Cidacos
transect. The highest grade is reached at the base of the Urbión Group, a fluvial sequence Upper
Jurassic to Lower Cretaceous in age (Weald facies). Physical conditions at the thermal peak are
estimated at abo 1 Kb (PL) and 326± 13°C (i.e. very low grade metamorphism). Fluids were largely
water brines with minor amounts of gases, CO2 and CH4• f02 and f52 were close to the graphite
and Po-Py buffers respectively. This metamorphism is spatially associated with a deformation band
(5-6 km. ín wídth) wíth schístosíty ín the pelitíc beds and promínent tensíonal, quartz ínfílled veíns
in the more samítíc ones. K-Ar dating on authígeníc illites has gíven ages from 108 to 86 M.a., i.e.
Míddle Cretaceous, and thus younger than the basín fílling (Urbíón Group+Enciso F.+Olívan F.).
Metamorphism migth be related wíth the circulatíon of hot mígratory fluíds (i.e. tectoníc brínes),
along the deformation bando The tectonic sígníficance of this deformation band is slill uncertain.