serie NOVA TERRA nº 49

77 deposition of turbiditic rocks in intra-arc basins, regional deformation, and the intrusion of a swarm of diabase dykes, suggest a very dynamic setting, which is typical of volcanic arcs developed on active con- tinental margins or of island arcs. Structuralanalysis of thelowest grade partofthe upper unitallowsthe oldestdynamichistoryofthisterranetobeexamined.Thisstudydescribes the structure of D 1 in the turbiditic series above the D 2 deformation front, and the link between the younger deformation to the pervasive regional Fig. 7. Rare earth element (REE) patterns for the different age groups de fi ned by the Ares dyke zircon crystals, illustrating their magmatic character. R33 zircon standard patterns are shown for reference (grey area), Chondrite normalization values after Anders and Grevesse (1989) modi fi ed by Korotev (1996) . Fig. 8. Plots of (a) Yb/Gd versus Th/U, and (b) Ce/Sm versus Yb/Gd for the zircon grains analyzed in the Ares dyke. Data from R33 zircon standard (open diamonds) are included for comparison and typical magmatic fractionation trends for the standard are shown. 360 F. Díaz García et al. / Gondwana Research 17 (2010) 352 – 362