Uranium Contents in the Lithological Formations of Santiago Island, Cape Verde

We present the uranium contents in the different lithological formations of Santiago. The island is constituted by basaltic-basanite rocks, but phonolitic-trachytic rocks also occur. The highest contents of uranium occur in the phonolitic-trachytics rocks of Ancient Complex and Pico Antónia Formations, and also in other formations of heterogeneous materials, which have phonolitic-trachytics fragments, reaching 62.8μg.g-1 of uranium. These contents are much higher than those of the MORB (0.047-0.18μg g-1) and OIB (1.02μg.g-1) and even higher than those of the upper crust. The source of uranium in the rocks of Santiago is related with the occurrence of zircon