| Abstract: | K-Ar measurements on minerals extracted from alkaline magmatic rocks evenly distributed along the Pyrenean belt show that magmatic activity took place between 110 and 85 Ma. Three age groups are observed: the first falls around 110 Ma, the second and by far the most important, within the interval 100-90 Ma and the third, restricted to samples from the far western part of the belt, within the interval 90-85 Ma. K-Ar dates on mesozonal metamorphics constitute two groups: the first corresponds to a cluster around 95 Ma while the second falls in the 87-81 Ma range.Assuming that magmatism on land is a tracer of the rotation of the Iberian Peninsula relative to Europe, we propose that the phenomenon took place between 110 Ma and 85 Ma. This conclusion agrees well with that recently put forward by marine geophysicists. On the other hand, our results on metamorphics confirm that the main phase of metamorphism in the Pyrenees is disconnected from the most important tectonic motions. Doubts remain, however, as to the interpretation of the two groups of data. In the light of our results, it cannot be said whether they correspond to one or two metamorphic phases. |
