The Cameros Basin ( N W o f the Iberian Range) is m a in ly composed o f very homogeneous silicic d e tr ita l m aterials in Weald facies. The occurrence o f c h lo rito id , cookeite, p y rite an d muscovite/p aragonite is related to a cretacic very low grade metamorphism. The geochemical analysis of this materials displays differences linked to lithologic features; comparison between metamorphic and no metamorphic materials shows no main differences in the chemical contents, but in the relationships between elements