| Popis: |
The Upper Neoproterozoic shales of the West Asturian-Leonese and Cantabrian Zones are geochemically very homogeneous and show similar mean contents of Zr, Hf, Nb, rare earth elements, Y, Th, U, V, Cr, Co and Ni andelement ratios such as A!2OJTiOy Rb/Zr, (LalYb)n, Th/Yb, Ti/Zr, and Ti/Nb. The Lower Cambrian shales in the same Zones are'not as homogeneous although their Al2OJTiOy Rb/Zr, (La/Yb)n, Th/Yb, Ti/Zr, and Cr/Zr average ratios are systematically higher, and the Ti/Nb ratio lower, than those of the Upper Neoproterozoic.rocks. These distinctive features are coincident with those of the corresponding shales in the Central Iberian Zone. Thus, the geochemical data strongly support the notion that all three Zones shared a very extensive and homogeneous source area |
