Geochemistry of the polymetamorphic mafic-ultramafic complex at Cabo Ortegal (NW Spain)

The Paleozoic Cabo Ortegal complex (Galicia, NW Spain) contains (1) a mafic rock series, now high-grade metamorphic rocks, that is equivalent to modern continental plateau basalts; this can be deduced from its trace element ‘fingerprint’, the [La/Sm]_a ratio of 3.25 and the quartz normative composition, (2) a younger mafic rock series equivalent to modern (Icelandic) ‘plume’ tholeiites, as can be inferred again from the trace element ‘fingerprint’, the [La/Sm]_a ratio of around unity and the olivine normative composition, (3) an ultramafic rock series that was the melt phase and then the residual phase in two subsequent melting events as can be inferred from the low La, Sm, K, and Rb contents compared with the high [La/Sm]_a and K/Rb ratios. The data are fitted into an evolution model of continental rifting, mantle-plume diapirism and rejuvenation of the lowe, crust.