Geochemical characterization of serpentinites at Cabo Ortegal, northwestern Spain

Cabo Ortegal is one of the major ultramafic complexes outcropping in Iberia. Most rocks are variably serpentinized, and the characteristics of the process can be traced through the composition of the rocks. The major and trace elements change in the different units of the complex. Together with the wide range of oxygen isotope values (delta O-18 from 3.9 up to 6.6 parts per thousand), these changes lead to the conclusion that several stages of serpentinization took place at Cabo Ortegal. Each stage is characterized by the composition of the fluid that produced the serpentinization. Seawater does not have to be the main fluid in the process; ail ultimate stage of serpentinization can mask the characteristics of a previous one.